Janet 1.17.1-e1c4fc2 Documentation
(Other Versions:
1.16.1
1.15.0
1.13.1
1.12.2
1.11.1
1.10.1
1.9.1
1.8.1
1.7.0
1.6.0
1.5.1
1.5.0
1.4.0
1.3.1
)
Core API
Index
% %= * *= + ++ += - -- -= -> ->> -?> -?>> / /= < <= = > >= abstract? accumulate accumulate2 all all-bindings all-dynamics and any? apply array array/clear array/concat array/ensure array/fill array/insert array/new array/new-filled array/peek array/pop array/push array/remove array/slice array/trim array? as-> as-macro as?-> asm assert bad-compile bad-parse band blshift bnot boolean? bor brshift brushift buffer buffer/bit buffer/bit-clear buffer/bit-set buffer/bit-toggle buffer/blit buffer/clear buffer/fill buffer/format buffer/new buffer/new-filled buffer/popn buffer/push buffer/push-byte buffer/push-string buffer/push-word buffer/slice buffer/trim buffer? bxor bytes? cancel case cfunction? chr cli-main cmp comment comp compare compare< compare<= compare= compare> compare>= compif compile complement comptime compwhen cond coro count curenv debug debug/arg-stack debug/break debug/fbreak debug/lineage debug/stack debug/stacktrace debug/step debug/unbreak debug/unfbreak debugger-env dec deep-not= deep= def- default default-peg-grammar defer defglobal defmacro defmacro- defn defn- describe dictionary? disasm distinct doc doc* doc-format doc-of dofile drop drop-until drop-while dyn each eachk eachp edefer eflush empty? env-lookup eprin eprinf eprint eprintf error errorf ev/call ev/cancel ev/capacity ev/chan ev/chan-close ev/chunk ev/close ev/count ev/deadline ev/do-thread ev/full ev/gather ev/give ev/give-supervisor ev/go ev/read ev/rselect ev/select ev/sleep ev/spawn ev/spawn-thread ev/take ev/thread ev/thread-chan ev/with-deadline ev/write eval eval-string even? every? extreme false? fiber-fn fiber/can-resume? fiber/current fiber/getenv fiber/last-value fiber/maxstack fiber/new fiber/root fiber/setenv fiber/setmaxstack fiber/status fiber? file/close file/flush file/open file/popen file/read file/seek file/temp file/write filter find find-index first flatten flatten-into flush flycheck for forever forv freeze frequencies from-pairs function? gccollect gcinterval gcsetinterval generate gensym get get-in getline group-by hash idempotent? identity if-let if-not if-with import import* in inc index-of indexed? int/s64 int/u64 int? interleave interpose invert janet/build janet/config-bits janet/version juxt juxt* keep keys keyword keyword/slice keyword? kvs label last length let load-image load-image-dict loop macex macex1 maclintf make-env make-image make-image-dict map mapcat marshal match math/-inf math/abs math/acos math/acosh math/asin math/asinh math/atan math/atan2 math/atanh math/cbrt math/ceil math/cos math/cosh math/e math/erf math/erfc math/exp math/exp2 math/expm1 math/floor math/gamma math/hypot math/inf math/int-max math/int-min math/int32-max math/int32-min math/log math/log10 math/log1p math/log2 math/nan math/next math/pi math/pow math/random math/rng math/rng-buffer math/rng-int math/rng-uniform math/round math/seedrandom math/sin math/sinh math/sqrt math/tan math/tanh math/trunc max mean merge merge-into merge-module min mod module/add-paths module/cache module/expand-path module/find module/loaders module/loading module/paths nan? nat? native neg? net/accept net/accept-loop net/address net/chunk net/close net/connect net/flush net/listen net/read net/recv-from net/send-to net/server net/shutdown net/write next nil? not not= number? odd? one? or os/arch os/cd os/chmod os/clock os/cryptorand os/cwd os/date os/dir os/environ os/execute os/exit os/getenv os/link os/lstat os/mkdir os/mktime os/open os/perm-int os/perm-string os/pipe os/proc-close os/proc-kill os/proc-wait os/readlink os/realpath os/rename os/rm os/rmdir os/setenv os/shell os/sleep os/spawn os/stat os/symlink os/time os/touch os/umask os/which pairs parse parser/byte parser/clone parser/consume parser/eof parser/error parser/flush parser/has-more parser/insert parser/new parser/produce parser/state parser/status parser/where partial partition partition-by peg/compile peg/find peg/find-all peg/match peg/replace peg/replace-all pos? postwalk pp prewalk prin prinf print printf product prompt propagate protect put put-in quit range reduce reduce2 repeat repl require resume return reverse reverse! root-env run-context scan-number seq setdyn short-fn signal slice slurp some sort sort-by sorted sorted-by spit stderr stdin stdout string string/ascii-lower string/ascii-upper string/bytes string/check-set string/find string/find-all string/format string/from-bytes string/has-prefix? string/has-suffix? string/join string/repeat string/replace string/replace-all string/reverse string/slice string/split string/trim string/triml string/trimr string? struct struct? sum symbol symbol/slice symbol? table table/clear table/clone table/getproto table/new table/rawget table/setproto table/to-struct table? take take-until take-while thread/close thread/current thread/exit thread/new thread/receive thread/send trace tracev true? truthy? try tuple tuple/brackets tuple/setmap tuple/slice tuple/sourcemap tuple/type tuple? type unless unmarshal untrace update update-in use values var- varfn varglobal walk warn-compile when when-let when-with with with-dyns with-syms with-vars xprin xprinf xprint xprintf yield zero? zipcoll
(% dividend divisor) Returns the remainder of dividend / divisor.
(% 10 3) # -> 1
(% -10 3) # -> -1
(% 10 -3) # -> 1
(% -10 -3) # -> -1
(% 1.4 1) # -> 0.4
(% -1.4 1) # -> -0.4
(% 1.4 1) # -> 0.4
(% -1.4 1) # -> -0.4
(% -1.4 0) # -> -nan
(% -1.4 0) # -> -nan
Community Examples(%= x n) Shorthand for (set x (% x n)).
(var x 10) # -> 10
(%= x 3) # -> 1
x # -> 1
Community Examples(* & xs) Returns the product of all elements in xs. If xs is empty, returns 1.
(*) # -> 1
(* 10) # -> 10
(* 10 20) # -> 200
(* 1 2 3 4 5 6 7) #-> 5040
# Can take product of array with splice, but 'product' is better
(* ;(range 1 20)) #-> 1.21645e+17
(product (range 1 20)) #-> 1.21645e+17
Community Examples(*= x n) Shorthand for (set x (* x n)).
(var x 100) # -> 100
x # -> 100
(*= x 10) # -> 1000
x # -> 1000
Community Examples(+ & xs) Returns the sum of all xs. xs must be integers or real numbers only. If xs is empty, return 0.
(+) # -> 0
(+ 10) # -> 10
(+ 1 2) # -> 3
(+ 1.4 -4.5) # -> -3.1
(+ 1 2 3 4 5 6 7 8 9 10) # -> 55
# Splice can be used to sum arrays, but 'sum' is better
(+ ;(range 101)) # -> 5050
(sum (range 101)) # -> 5050
# Janet can add types that support the :+ or :r+ method
(+ (int/s64 "10") 10) # -> <core/s64 20>
# Bad types give errors
(+ nil 10) # -> error: could not find method :+ for nil, or :r+ for 10
Community Examples(+= x n) Increments the var x by n.
(var x 100) # -> 100
x # -> 100
(+= x 10) # -> 110
x # -> 110
Community Examples(- & xs) Returns the difference of xs. If xs is empty, returns 0. If xs has one element, returns the negative value of that element. Otherwise, returns the first element in xs minus the sum of the rest of the elements.
(-) # -> 0
(- 10) # -> -10
(- 1 2) # -> -1
(+ 1.4 -4.5) # -> 5.9
# Equivalent to (- first (+ ;rest))
(- 1 2 3 4 5 6 7 8 9 10) # -> -53
# Janet can subtract types that support the :- or :r- method
(- (int/s64 "10") 10) # -> <core/s64 0>
Community Examples(-= x n) Decrements the var x by n.
(var x 10) # -> 10
(-= x 20) # -> -10
x # -> -10
Community Examples(-> x & forms) Threading macro. Inserts x as the second value in the first form in forms, and inserts the modified first form into the second form in the same manner, and so on. Useful for expressing pipelines of data.Community Examples
(->> x & forms) Threading macro. Inserts x as the last value in the first form in forms, and inserts the modified first form into the second form in the same manner, and so on. Useful for expressing pipelines of data.Community Examples
(-?> x & forms) Short circuit threading macro. Inserts x as the second value in the first form in forms, and inserts the modified first form into the second form in the same manner, and so on. The pipeline will return nil if an intermediate value is nil. Useful for expressing pipelines of data.Community Examples
(-?>> x & forms) Short circuit threading macro. Inserts x as the last value in the first form in forms, and inserts the modified first form into the second form in the same manner, and so on. The pipeline will return nil if an intermediate value is nil. Useful for expressing pipelines of data.Community Examples
(/ & xs) Returns the quotient of xs. If xs is empty, returns 1. If xs has one value x, returns the reciprocal of x. Otherwise return the first value of xs repeatedly divided by the remaining values.Community Examples
(accumulate f init ind) Similar to reduce, but accumulates intermediate values into an array. The last element in the array is what would be the return value from reduce. The init value is not added to the array (the return value will have the same number of elements as ind). Returns a new array.Community Examples
(accumulate2 f ind) The 2-argument version of accumulate that does not take an initialization value. The first value in ind will be added to the array as is, so the length of the return value will be (length ind).Community Examples
(all pred xs) Returns true if all xs are truthy, otherwise the result of first falsey predicate value, (pred x).Community Examples
(all-bindings &opt env local) Get all symbols available in an environment. Defaults to the current fiber's environment. If local is truthy, will not show inherited bindings (from prototype tables).Community Examples
(all-dynamics &opt env local) Get all dynamic bindings in an environment. Defaults to the current fiber's environment. If local is truthy, will not show inherited bindings (from prototype tables).Community Examples
(and & forms) Evaluates to the last argument if all preceding elements are truthy, otherwise evaluates to the first falsey argument.Community Examples
(any? ind) Returns the first truthy value in ind, otherwise nil. falsey value.Community Examples
(apply f & args) Applies a function to a variable number of arguments. Each element in args is used as an argument to f, except the last element in args, which is expected to be an array-like. Each element in this last argument is then also pushed as an argument to f. For example: (apply + 1000 (range 10)) sums the first 10 integers and 1000.
(apply + (range 10)) # -> 45
(apply + []) # -> 0
(apply + 1 2 3 4 5 6 7 [8 9 10]) # -> 55
(apply + 1 2 3 4 5 6 7 8 9 10) # -> error: expected array|tuple, got number
# Can also be used to call macros like functions.
# Will return the macro expanded code of the original macro.
(apply for 'x 0 10 ['(print x)])
# -> (do (var _000000 0) (def _000001 10) (while ...
Community Examples(array & items) Create a new array that contains items. Returns the new array.Community Examples
(array/clear arr) Empties an array, setting it's count to 0 but does not free the backing capacity. Returns the modified array.Community Examples
(array/concat arr & parts) Concatenates a variable number of arrays (and tuples) into the first argument, which must be an array. If any of the parts are arrays or tuples, their elements will be inserted into the array. Otherwise, each part in `parts` will be appended to `arr` in order. Return the modified array `arr`.Community Examples
(array/ensure arr capacity growth) Ensures that the memory backing the array is large enough for `capacity` items at the given rate of growth. Capacity and growth must be integers. If the backing capacity is already enough, then this function does nothing. Otherwise, the backing memory will be reallocated so that there is enough space.Community Examples
(array/fill arr &opt value) Replace all elements of an array with `value` (defaulting to nil) without changing the length of the array. Returns the modified array.Community Examples
(array/insert arr at & xs) Insert all `xs` into array `arr` at index `at`. `at` should be an integer between 0 and the length of the array. A negative value for `at` will index backwards from the end of the array, such that inserting at -1 appends to the array. Returns the array.Community Examples
(array/new capacity) Creates a new empty array with a pre-allocated capacity. The same as (array) but can be more efficient if the maximum size of an array is known.
(def arr (array/new 100)) # -> @[]
# Now we can fill up the array without triggering a resize
(for i 0 100
(put arr i i))
Community Examples(array/new-filled count &opt value) Creates a new array of `count` elements, all set to `value`, which defaults to nil. Returns the new array.Community Examples
(array/peek arr) Returns the last element of the array. Does not modify the array.Community Examples
(array/pop arr) Remove the last element of the array and return it. If the array is empty, will return nil. Modifies the input array.Community Examples
(array/push arr x) Insert an element in the end of an array. Modifies the input array and returns it.Community Examples
(array/remove arr at &opt n) Remove up to `n` elements starting at index `at` in array `arr`. `at` can index from the end of the array with a negative index, and `n` must be a non-negative integer. By default, `n` is 1. Returns the array.Community Examples
(array/slice arrtup &opt start end) Takes a slice of array or tuple from `start` to `end`. The range is half open, [start, end). Indexes can also be negative, indicating indexing from the end of the array. By default, `start` is 0 and `end` is the length of the array. Note that index -1 is synonymous with index `(length arrtup)` to allow a full negative slice range. Returns a new array.Community Examples
(array/trim arr) Set the backing capacity of an array to its current length. Returns the modified array.Community Examples
(as-> x as & forms) Thread forms together, replacing as in forms with the value of the previous form. The first for is the value x. Returns the last value.Community Examples
(as-macro f & args) Use a function or macro literal `f` as a macro. This lets any function be used as a macro. Inside a quasiquote, the idiom `(as-macro ,my-custom-macro arg1 arg2...)` can be used to avoid unwanted variable capture.Community Examples
(as?-> x as & forms) Thread forms together, replacing as in forms with the value of the previous form. The first for is the value x. If any intermediate values are falsey, return nil; otherwise, returns the last value.Community Examples
(asm assembly) Returns a new function that is the compiled result of the assembly. The syntax for the assembly can be found on the Janet website, and should correspond to the return value of disasm. Will throw an error on invalid assembly.Community Examples
(assert x &opt err) Throw an error if x is not truthy. Will not evaluate `err` if x is truthy.Community Examples
(bad-compile msg macrof where &opt line col) Default handler for a compile error.Community Examples
(band & xs) Returns the bit-wise and of all values in xs. Each x in xs must be an integer.Community Examples
(blshift x & shifts) Returns the value of x bit shifted left by the sum of all values in shifts. x and each element in shift must be an integer.Community Examples
(bor & xs) Returns the bit-wise or of all values in xs. Each x in xs must be an integer.Community Examples
(brshift x & shifts) Returns the value of x bit shifted right by the sum of all values in shifts. x and each element in shift must be an integer.Community Examples
(brushift x & shifts) Returns the value of x bit shifted right by the sum of all values in shifts. x and each element in shift must be an integer. The sign of x is not preserved, so for positive shifts the return value will always be positive.Community Examples
(buffer & xs) Creates a buffer by concatenating the elements of `xs` together. If an element is not a byte sequence, it is converted to bytes via `describe`. Returns the new buffer.Community Examples
(buffer/bit buffer index) Gets the bit at the given bit-index. Returns true if the bit is set, false if not.Community Examples
(buffer/bit-clear buffer index) Clears the bit at the given bit-index. Returns the buffer.Community Examples
(buffer/bit-set buffer index) Sets the bit at the given bit-index. Returns the buffer.Community Examples
(buffer/bit-toggle buffer index) Toggles the bit at the given bit index in buffer. Returns the buffer.Community Examples
(buffer/blit dest src &opt dest-start src-start src-end) Insert the contents of src into dest. Can optionally take indices that indicate which part of src to copy into which part of dest. Indices can be negative to index from the end of src or dest. Returns dest.Community Examples
(buffer/clear buffer) Sets the size of a buffer to 0 and empties it. The buffer retains its memory so it can be efficiently refilled. Returns the modified buffer.Community Examples
(buffer/fill buffer &opt byte) Fill up a buffer with bytes, defaulting to 0s. Does not change the buffer's length. Returns the modified buffer.Community Examples
(buffer/format buffer format & args) Snprintf like functionality for printing values into a buffer. Returns the modified buffer.Community Examples
(buffer/new capacity) Creates a new, empty buffer with enough backing memory for capacity bytes. Returns a new buffer of length 0.Community Examples
(buffer/new-filled count &opt byte) Creates a new buffer of length count filled with byte. By default, byte is 0. Returns the new buffer.Community Examples
(buffer/popn buffer n) Removes the last n bytes from the buffer. Returns the modified buffer.Community Examples
(buffer/push buffer & xs) Push both individual bytes and byte sequences to a buffer. For each x in xs, push the byte if x is an integer, otherwise push the bytesequence to the buffer. Thus, this function behaves like both `buffer/push-string` and `buffer/push-byte`. Returns the modified buffer. Will throw an error if the buffer overflows.Community Examples
(buffer/push-byte buffer & xs) Append bytes to a buffer. Will expand the buffer as necessary. Returns the modified buffer. Will throw an error if the buffer overflows.Community Examples
(buffer/push-string buffer & xs) Push byte sequences onto the end of a buffer. Will accept any of strings, keywords, symbols, and buffers. Returns the modified buffer. Will throw an error if the buffer overflows.Community Examples
(buffer/push-word buffer & xs) Append machine words to a buffer. The 4 bytes of the integer are appended in twos complement, little endian order, unsigned for all x. Returns the modified buffer. Will throw an error if the buffer overflows.Community Examples
(buffer/slice bytes &opt start end) Takes a slice of a byte sequence from start to end. The range is half open, [start, end). Indexes can also be negative, indicating indexing from the end of the end of the array. By default, start is 0 and end is the length of the buffer. Returns a new buffer.Community Examples
(buffer/trim buffer) Set the backing capacity of the buffer to the current length of the buffer. Returns the modified buffer.Community Examples
(bxor & xs) Returns the bit-wise xor of all values in xs. Each in xs must be an integer.Community Examples
(bytes? x) Check if x is a string, symbol, keyword, or buffer.Community Examples
(cancel fiber err) Resume a fiber but have it immediately raise an error. This lets a programmer unwind a pending fiber. Returns the same result as resume.Community Examples
(case dispatch & pairs) Select the body that equals the dispatch value. When pairs has an odd number of arguments, the last is the default expression. If no match is found, returns nil.Community Examples
(chr c) Convert a string of length 1 to its byte (ascii) value at compile time.Community Examples
(cli-main args) Entrance for the Janet CLI tool. Call this function with the command line arguments as an array or tuple of strings to invoke the CLI interface.Community Examples
(cmp x y) Returns -1 if x is strictly less than y, 1 if y is strictly greater than x, and 0 otherwise. To return 0, x and y must be the exact same type.Community Examples
(comp & functions) Takes multiple functions and returns a function that is the composition of those functions.Community Examples
(compare x y) Polymorphic compare. Returns -1, 0, 1 for x < y, x = y, x > y respectively. Differs from the primitive comparators in that it first checks to see whether either x or y implement a `compare` method which can compare x and y. If so, it uses that method. If not, it delegates to the primitive comparators.Community Examples
(compare< & xs) Equivalent of `<` but using polymorphic `compare` instead of primitive comparator.Community Examples
(compare<= & xs) Equivalent of `<=` but using polymorphic `compare` instead of primitive comparator.Community Examples
(compare= & xs) Equivalent of `=` but using polymorphic `compare` instead of primitive comparator.Community Examples
(compare> & xs) Equivalent of `>` but using polymorphic `compare` instead of primitive comparator.Community Examples
(compare>= & xs) Equivalent of `>=` but using polymorphic `compare` instead of primitive comparator.Community Examples
(compif cnd tru &opt fals) Check the condition cnd at compile time - if truthy, compile tru, else compile fals.Community Examples
(compile ast &opt env source lints) Compiles an Abstract Syntax Tree (ast) into a function. Pair the compile function with parsing functionality to implement eval. Returns a new function and does not modify ast. Returns an error struct with keys :line, :column, and :error if compilation fails. If a `lints` array is given, linting messages will be appended to the array. Each message will be a tuple of the form `(level line col message)`.Community Examples
(complement f) Returns a function that is the complement to the argument.Community Examples
(comptime x) Evals x at compile time and returns the result. Similar to a top level unquote.Community Examples
(compwhen cnd & body) Check the condition cnd at compile time - if truthy, compile (upscope ;body), else compile nil.Community Examples
(cond & pairs) Evaluates conditions sequentially until the first true condition is found, and then executes the corresponding body. If there are an odd number of forms, and no forms are matched, the last expression is executed. If there are no matches, return nil.Community Examples
(coro & body) A wrapper for making fibers that may yield multiple values (coroutine). Same as (fiber/new (fn [] ;body) :yi).Community Examples
(count pred ind) Count the number of items in ind for which (pred item) is true.Community Examples
(curenv &opt n) Get the current environment table. Same as (fiber/getenv (fiber/current)). If n is provided, gets the nth prototype of the environment table.Community Examples
(debug &opt x) Throws a debug signal that can be caught by a parent fiber and used to inspect the running state of the current fiber. Returns the value passed in by resume.Community Examples
(debug/arg-stack fiber) Gets all values currently on the fiber's argument stack. Normally, this should be empty unless the fiber signals while pushing arguments to make a function call. Returns a new array.Community Examples
(debug/break source line col) Sets a breakpoint in `source` at a given line and column. Will throw an error if the breakpoint location cannot be found. For example (debug/break "core.janet" 10 4) will set a breakpoint at line 10, 4th column of the file core.janet.Community Examples
(debug/fbreak fun &opt pc) Set a breakpoint in a given function. pc is an optional offset, which is in bytecode instructions. fun is a function value. Will throw an error if the offset is too large or negative.Community Examples
(debug/lineage fib) Returns an array of all child fibers from a root fiber. This function is useful when a fiber signals or errors to an ancestor fiber. Using this function, the fiber handling the error can see which fiber raised the signal. This function should be used mostly for debugging purposes.Community Examples
(debug/stack fib) Gets information about the stack as an array of tables. Each table in the array contains information about a stack frame. The top-most, current stack frame is the first table in the array, and the bottom-most stack frame is the last value. Each stack frame contains some of the following attributes: * :c - true if the stack frame is a c function invocation * :column - the current source column of the stack frame * :function - the function that the stack frame represents * :line - the current source line of the stack frame * :name - the human-friendly name of the function * :pc - integer indicating the location of the program counter * :source - string with the file path or other identifier for the source code * :slots - array of all values in each slot * :tail - boolean indicating a tail callCommunity Examples
(debug/stacktrace fiber &opt err) Prints a nice looking stacktrace for a fiber. Can optionally provide an error value to print the stack trace with. If `err` is nil or not provided, will skip the error line. Returns the fiber.Community Examples
(debug/step fiber &opt x) Run a fiber for one virtual instruction of the Janet machine. Can optionally pass in a value that will be passed as the resuming value. Returns the signal value, which will usually be nil, as breakpoints raise nil signals.Community Examples
(debug/unbreak source line column) Remove a breakpoint with a source key at a given line and column. Will throw an error if the breakpoint cannot be found.Community Examples
(debug/unfbreak fun &opt pc) Unset a breakpoint set with debug/fbreak.Community Examples
An environment that contains dot prefixed functions for debugging.Community Examples
(deep-not= x y) Like not=, but mutable types (arrays, tables, buffers) are considered equal if they have identical structure. Much slower than not=.Community Examples
(deep= x y) Like =, but mutable types (arrays, tables, buffers) are considered equal if they have identical structure. Much slower than =.Community Examples
(def- name & more) Define a private value that will not be exported.
# In a file module.janet
(def- private-thing :encapsulated)
(def public-thing :exposed)
# In a file main.janet
(import module)
module/private-thing # -> Unknown symbol
module/public-thing # -> :exposed
# Same as normal def with :private metadata
(def :private x private-thing :encapsulated)
Community Examples(default sym val) Define a default value for an optional argument. Expands to (def sym (if (= nil sym) val sym))Community Examples
The default grammar used for pegs. This grammar defines several common patterns that should make it easier to write more complex patterns.Community Examples
(defer form & body) Run form unconditionally after body, even if the body throws an error. Will also run form if a user signal 0-4 is received.
# Evaluates to 6 after printing "scope left!"
(defer (print "scope left!")
(+ 1 2 3))
# cleanup will always be called, even if there is a failure
(defer (cleanup)
(step-1)
(step-2)
(if (< 0.1 (math/random)) (error "failure"))
(step-3))
Community Examples(defmacro- name & more) Define a private macro that will not be exported.Community Examples
(defn name & more) Define a function. Equivalent to (def name (fn name [args] ...)).
(defn simple
[x]
(print (+ x 1)))
(simple 10) # -> 11
(defn long-body
[y]
(print y)
(print (+ y 1))
(print (+ y 2))
(+ y 3))
(defn with-docstring
"This function has a docstring"
[]
(print "hello!"))
(defn with-tags
:tag1 :tag2 :private
"Also has a docstring and a variadic argument 'more'!"
[x y z & more]
[x y z more])
(with-tags 1 2) # raises arity error
(with-tags 1 2 3) # -> (1 2 3 ())
(with-tags 1 2 3 4) # -> (1 2 3 (4))
(with-tags 1 2 3 4 5) # -> (1 2 3 (4 5))
# Tags (and other metadata) are (usually) visible in the environment.
(dyn 'with-tags) # -> @{:tag2 true :value <function with-tags> :doc "(with-tags x y z & more)\n\nAlso has a docstring..." :source-map ("repl" 4 1) :tag1 true :private true}
Community Examples(defn- name & more) Define a private function that will not be exported.
# In a file module.janet
(defn- not-exposed-fn
[x]
(+ x x))
(not-exposed-fn 10) # -> 20
# In a file main.janet
(import module)
(module/not-exposed-fn 10) # -> Unknown symbol error
# Same as
(defn not-exposed-fn
:private
[x]
(+ x x))
Community Examples(describe x) Returns a string that is a human-readable description of a value x.Community Examples
(disasm func &opt field) Returns assembly that could be used to compile the given function. func must be a function, not a c function. Will throw on error on a badly typed argument. If given a field name, will only return that part of the function assembly. Possible fields are: * :arity - number of required and optional arguments. * :min-arity - minimum number of arguments function can be called with. * :max-arity - maximum number of arguments function can be called with. * :vararg - true if function can take a variable number of arguments. * :bytecode - array of parsed bytecode instructions. Each instruction is a tuple. * :source - name of source file that this function was compiled from. * :name - name of function. * :slotcount - how many virtual registers, or slots, this function uses. Corresponds to stack space used by function. * :constants - an array of constants referenced by this function. * :sourcemap - a mapping of each bytecode instruction to a line and column in the source file. * :environments - an internal mapping of which enclosing functions are referenced for bindings. * :defs - other function definitions that this function may instantiate.Community Examples
(distinct xs) Returns an array of the deduplicated values in xs.Community Examples
(doc &opt sym) Shows documentation for the given symbol, or can show a list of available bindings. If `sym` is a symbol, will look for documentation for that symbol. If `sym` is a string or is not provided, will show all lexical and dynamic bindings in the current environment containing that string (all bindings will be shown if no string is given).Community Examples
(doc* &opt sym) Get the documentation for a symbol in a given environment. Function form of doc.Community Examples
(doc-format str &opt width indent colorize) Reformat a docstring to wrap a certain width. Docstrings can either be plaintext or a subset of markdown. This allows a long single line of prose or formatted text to be a well-formed docstring. Returns a buffer containing the formatted text.Community Examples
(doc-of x) Searches all loaded modules in module/cache for a given binding and prints out its documentation. This does a search by value instead of by name. Returns nil.Community Examples
(dofile path &keys {:read read :parser parser :source src :evaluator evaluator :expander expander :env env :exit exit}) Evaluate a file and return the resulting environment. :env, :expander, :evaluator, :read, and :parser are passed through to the underlying run-context call. If exit is true, any top level errors will trigger a call to (os/exit 1) after printing the error.Community Examples
(drop n ind) Drop the first n elements in an indexed or bytes type. Returns a new tuple or string instance, respectively.Community Examples
(drop-until pred ind) Same as `(drop-while (complement pred) ind)`.Community Examples
(drop-while pred ind) Given a predicate, remove elements from an indexed or bytes type that satisfy the predicate, and abort on first failure. Returns a new tuple or string, respectively.Community Examples
(dyn key &opt default) Get a dynamic binding. Returns the default value (or nil) if no binding found.Community Examples
(eachp x ds & body) Loop over each (key, value) pair in ds. Returns nil.Community Examples
(edefer form & body) Run form after body in the case that body terminates abnormally (an error or user signal 0-4). Otherwise, return last form in body.
# Half of the time, return "ok", the other
# half of the time, print there was an error and throw "oops".
(edefer (print "there was an error")
(if (< (math/random) 0.5)
(error "oops")
"ok"))
Community Examples(eflush) Flush (dyn :err stderr) if it is a file, otherwise do nothing.Community Examples
(env-lookup env) Creates a forward lookup table for unmarshalling from an environment. To create a reverse lookup table, use the invert function to swap keys and values in the returned table.Community Examples
(eprin & xs) Same as prin, but uses (dyn :err stderr) instead of (dyn :out stdout).Community Examples
(eprinf fmt & xs) Like eprintf but with no trailing newline.Community Examples
(eprint & xs) Same as print, but uses (dyn :err stderr) instead of (dyn :out stdout).Community Examples
(eprintf fmt & xs) Prints output formatted as if with (string/format fmt ;xs) to (dyn :err stderr) with a trailing newline.Community Examples
(error e) Throws an error e that can be caught and handled by a parent fiber.Community Examples
(errorf fmt & args) A combination of error and string/format. Equivalent to (error (string/format fmt ;args))Community Examples
(ev/call f & args) Call a function asynchronously. Returns a fiber that is scheduled to run the function.Community Examples
(ev/cancel fiber err) Cancel a suspended fiber in the event loop. Differs from cancel in that it returns the canceled fiber immediatelyCommunity Examples
(ev/capacity channel) Get the number of items a channel will store before blocking writers.Community Examples
(ev/chan &opt capacity) Create a new channel. capacity is the number of values to queue before blocking writers, defaults to 0 if not provided. Returns a new channel.Community Examples
(ev/chan-close chan) Close a channel. A closed channel will cause all pending reads and writes to return nil. Returns the channel.Community Examples
(ev/chunk stream n &opt buffer timeout) Same as ev/read, but will not return early if less than n bytes are available. If an end of stream is reached, will also return early with the collected bytes.Community Examples
(ev/close stream) Close a stream. This should be the same as calling (:close stream) for all streams.Community Examples
(ev/count channel) Get the number of items currently waiting in a channel.Community Examples
(ev/deadline sec &opt tocancel tocheck) Set a deadline for a fiber `tocheck`. If `tocheck` is not finished after `sec` seconds, `tocancel` will be canceled as with `ev/cancel`. If `tocancel` and `tocheck` are not given, they default to `(fiber/root)` and `(fiber/current)` respectively. Returns `tocancel`.Community Examples
(ev/do-thread & body) Run some code in a new thread. Suspends the current fiber until the thread is complete, and evaluates to nil.Community Examples
(ev/gather & bodies) Run a number of fibers in parallel on the event loop, and join when they complete. Returns the gathered results in an array.Community Examples
(ev/give channel value) Write a value to a channel, suspending the current fiber if the channel is full. Returns the channel if the write succeeded, nil otherwise.Community Examples
(ev/give-supervisor tag & payload) Send a message to the current supervior channel if there is one. The message will be a tuple of all of the arguments combined into a single message, where the first element is tag. By convention, tag should be a keyword indicating the type of message. Returns nil.Community Examples
(ev/go fiber &opt value supervisor) Put a fiber on the event loop to be resumed later. Optionally pass a value to resume with, otherwise resumes with nil. Returns the fiber. An optional `core/channel` can be provided as a supervisor. When various events occur in the newly scheduled fiber, an event will be pushed to the supervisor. If not provided, the new fiber will inherit the current supervisor.Community Examples
(ev/read stream n &opt buffer timeout) Read up to n bytes into a buffer asynchronously from a stream. `n` can also be the keyword `:all` to read into the buffer until end of stream. Optionally provide a buffer to write into as well as a timeout in seconds after which to cancel the operation and raise an error. Returns the buffer if the read was successful or nil if end-of-stream reached. Will raise an error if there are problems with the IO operation.Community Examples
(ev/rselect & clauses) Similar to ev/select, but will try clauses in a random order for fairness.Community Examples
(ev/select & clauses) Block until the first of several channel operations occur. Returns a tuple of the form [:give chan], [:take chan x], or [:close chan], where a :give tuple is the result of a write and :take tuple is the result of a read. Each clause must be either a channel (for a channel take operation) or a tuple [channel x] for a channel give operation. Operations are tried in order, such that the first clauses will take precedence over later clauses. Both and give and take operations can return a [:close chan] tuple, which indicates that the specified channel was closed while waiting, or that the channel was already closed.Community Examples
(ev/sleep sec) Suspend the current fiber for sec seconds without blocking the event loop.Community Examples
(ev/spawn & body) Run some code in a new fiber. This is shorthand for (ev/call (fn [] ;body)).Community Examples
(ev/spawn-thread & body) Run some code in a new thread. Like `ev/do-thread`, but returns nil immediately.Community Examples
(ev/take channel) Read from a channel, suspending the current fiber if no value is available.Community Examples
(ev/thread fiber &opt value flags supervisor) Resume a (copy of a) `fiber` in a new operating system thread, optionally passing `value` to resume with. Unlike `ev/go`, this function will suspend the current fiber until the thread is complete. If you want to run the thread without waiting for a result, pass the `:n` flag to return nil immediately. Otherwise, returns nil. Available flags: * `:n` - return immediately * `:a` - don't copy abstract registry to new thread (performance optimization) * `:c` - don't copy cfunction registry to new thread (performance optimization)Community Examples
(ev/thread-chan &opt limit) Create a threaded channel. A threaded channel is a channel that can be shared between threads and used to communicate between any number of operating system threads.Community Examples
(ev/with-deadline deadline & body) Run a body of code with a deadline, such that if the code does not complete before the deadline is up, it will be canceled.Community Examples
(ev/write stream data &opt timeout) Write data to a stream, suspending the current fiber until the write completes. Takes an optional timeout in seconds, after which will return nil. Returns nil, or raises an error if the write failed.Community Examples
(eval form) Evaluates a form in the current environment. If more control over the environment is needed, use `run-context`.
(eval '(+ 1 2 3)) # -> 6
(eval '(error :oops)) # -> raises error :oops
(eval '(+ nil nil)) # -> raises error
Community Examples(eval-string str) Evaluates a string in the current environment. If more control over the environment is needed, use `run-context`.
(eval-string "(+ 1 2 3 4)") # -> 10
(eval-string ")") # -> parse error
(eval-string "(bloop)") # -> compile error
(eval-string "(+ nil nil)") # -> runtime error
Community Examples(every? ind) Returns true if each value in is truthy, otherwise the first falsey value.Community Examples
(extreme order args) Returns the most extreme value in args based on the function order. order should take two values and return true or false (a comparison). Returns nil if args is empty.Community Examples
(fiber-fn flags & body) A wrapper for making fibers. Same as (fiber/new (fn [] ;body) flags).Community Examples
(fiber/can-resume? fiber) Check if a fiber is finished and cannot be resumed.Community Examples
(fiber/current) Returns the currently running fiber.Community Examples
(fiber/getenv fiber) Gets the environment for a fiber. Returns nil if no such table is set yet.Community Examples
(fiber/last-value) Get the last value returned or signaled from the fiber.Community Examples
(fiber/maxstack fib) Gets the maximum stack size in janet values allowed for a fiber. While memory for the fiber's stack is not allocated up front, the fiber will not allocated more than this amount and will throw a stack-overflow error if more memory is needed.Community Examples
(fiber/new func &opt sigmask) Create a new fiber with function body func. Can optionally take a set of signals to block from the current parent fiber when called. The mask is specified as a keyword where each character is used to indicate a signal to block. If the ev module is enabled, and this fiber is used as an argument to `ev/go`, these "blocked" signals will result in messages being sent to the supervisor channel. The default sigmask is :y. For example, (fiber/new myfun :e123) blocks error signals and user signals 1, 2 and 3. The signals are as follows: * :a - block all signals * :d - block debug signals * :e - block error signals * :t - block termination signals: error + user[0-4] * :u - block user signals * :y - block yield signals * :0-9 - block a specific user signal The sigmask argument also can take environment flags. If any mutually exclusive flags are present, the last flag takes precedence. * :i - inherit the environment from the current fiber * :p - the environment table's prototype is the current environment tableCommunity Examples
(fiber/root) Returns the current root fiber. The root fiber is the oldest ancestor that does not have a parent.Community Examples
(fiber/setenv fiber table) Sets the environment table for a fiber. Set to nil to remove the current environment.Community Examples
(fiber/setmaxstack fib maxstack) Sets the maximum stack size in janet values for a fiber. By default, the maximum stack size is usually 8192.Community Examples
(fiber/status fib) Get the status of a fiber. The status will be one of: * :dead - the fiber has finished * :error - the fiber has errored out * :debug - the fiber is suspended in debug mode * :pending - the fiber has been yielded * :user(0-9) - the fiber is suspended by a user signal * :alive - the fiber is currently running and cannot be resumed * :new - the fiber has just been created and not yet runCommunity Examples
(file/close f) Close a file and release all related resources. When you are done reading a file, close it to prevent a resource leak and let other processes read the file. If the file is the result of a file/popen call, close waits for and returns the process exit status.Community Examples
(file/flush f) Flush any buffered bytes to the file system. In most files, writes are buffered for efficiency reasons. Returns the file handle.Community Examples
(file/open path &opt mode) Open a file. `path` is an absolute or relative path, and `mode` is a set of flags indicating the mode to open the file in. `mode` is a keyword where each character represents a flag. If the file cannot be opened, returns nil, otherwise returns the new file handle. Mode flags: * r - allow reading from the file * w - allow writing to the file * a - append to the file Following one of the initial flags, 0 or more of the following flags can be appended: * b - open the file in binary mode (rather than text mode) * + - append to the file instead of overwriting it * n - error if the file cannot be opened instead of returning nilCommunity Examples
(file/popen command &opt mode) (DEPRECATED for os/spawn) Open a file that is backed by a process. The file must be opened in either the :r (read) or the :w (write) mode. In :r mode, the stdout of the process can be read from the file. In :w mode, the stdin of the process can be written to. Returns the new file.Community Examples
(file/read f what &opt buf) Read a number of bytes from a file `f` into a buffer. A buffer `buf` can be provided as an optional third argument, otherwise a new buffer is created. `what` can either be an integer or a keyword. Returns the buffer with file contents. Values for `what`: * :all - read the whole file * :line - read up to and including the next newline character * n (integer) - read up to n bytes from the fileCommunity Examples
(file/seek f &opt whence n) Jump to a relative location in the file `f`. `whence` must be one of: * :cur - jump relative to the current file location * :set - jump relative to the beginning of the file * :end - jump relative to the end of the file By default, `whence` is :cur. Optionally a value `n` may be passed for the relative number of bytes to seek in the file. `n` may be a real number to handle large files of more than 4GB. Returns the file handle.Community Examples
(file/temp) Open an anonymous temporary file that is removed on close. Raises an error on failure.Community Examples
(file/write f bytes) Writes to a file. 'bytes' must be string, buffer, or symbol. Returns the file.Community Examples
(filter pred ind) Given a predicate, take only elements from an array or tuple for which (pred element) is truthy. Returns a new array.Community Examples
(find pred ind &opt dflt) Find the first value in an indexed collection that satisfies a predicate. Returns dflt if not found.Community Examples
(find-index pred ind &opt dflt) Find the index of indexed type for which pred is true. Returns dflt if not found.Community Examples
(first xs) Get the first element from an indexed data structure.Community Examples
(flatten xs) Takes a nested array (tree), and returns the depth first traversal of that array. Returns a new array.Community Examples
(flatten-into into xs) Takes a nested array (tree), and appends the depth first traversal of that array to an array 'into'. Returns array into.Community Examples
(flush) Flush (dyn :out stdout) if it is a file, otherwise do nothing.Community Examples
(flycheck path &keys kwargs) Check a file for errors without running the file. Found errors will be printed to stderr in the usual format. Macros will still be executed, however, so arbitrary execution is possible. Other arguments are the same as dofile. `path` can also be a file value such as stdin. Returns nil.Community Examples
(for i start stop & body) Do a C-style for-loop for side effects. Returns nil.Community Examples
(forever & body) Evaluate body forever in a loop, or until a break statement.Community Examples
(forv i start stop & body) Do a C-style for-loop for side effects. The iteration variable `i` can be mutated in the loop, unlike normal `for`. Returns nil.Community Examples
(freeze x) Freeze an object (make it immutable) and do a deep copy, making child values also immutable. Closures, fibers, and abstract types will not be recursively frozen, but all other types will.Community Examples
(frequencies ind) Get the number of occurrences of each value in a indexed structure.Community Examples
(from-pairs ps) Takes a sequence of pairs and creates a table from each pair. The inverse of `pairs` on a table.Community Examples
(function? x) Check if x is a function (not a cfunction).Community Examples
(gccollect) Run garbage collection. You should probably not call this manually.Community Examples
(gcinterval) Returns the integer number of bytes to allocate before running an iteration of garbage collection.Community Examples
(gcsetinterval interval) Set an integer number of bytes to allocate before running garbage collection. Low values for interval will be slower but use less memory. High values will be faster but use more memory.Community Examples
(generate head & body) Create a generator expression using the loop syntax. Returns a fiber that yields all values inside the loop in order. See loop for details.
# An infinite stream of random numbers, but doubled.
(def g (generate [_ :iterate true :repeat 2] (math/random)))
# -> <fiber 0x5562863141E0>
(resume g) # -> 0.487181
(resume g) # -> 0.487181
(resume g) # -> 0.507917
(resume g) # -> 0.507917
# ...
Community Examples(gensym) Returns a new symbol that is unique across the runtime. This means it will not collide with any already created symbols during compilation, so it can be used in macros to generate automatic bindings.Community Examples
(get ds key &opt dflt) Get the value mapped to key in data structure ds, and return dflt or nil if not found. Similar to in, but will not throw an error if the key is invalid for the data structure unless the data structure is an abstract type. In that case, the abstract type getter may throw an error.Community Examples
(get-in ds ks &opt dflt) Access a value in a nested data structure. Looks into the data structure via a sequence of keys.Community Examples
(getline &opt prompt buf env) Reads a line of input into a buffer, including the newline character, using a prompt. An optional environment table can be provided for auto-complete. Returns the modified buffer. Use this function to implement a simple interface for a terminal program.Community Examples
(group-by f ind) Group elements of `ind` by a function `f` and put the results into a table. The keys of the table are the distinct return values of `f`, and the values are arrays of all elements of `ind` that are equal to that value.Community Examples
(hash value) Gets a hash for any value. The hash is an integer can be used as a cheap hash function for all values. If two values are strictly equal, then they will have the same hash value.Community Examples
(idempotent? x) Check if x is a value that evaluates to itself when compiled.Community Examples
(if-let bindings tru &opt fal) Make multiple bindings, and if all are truthy, evaluate the tru form. If any are false or nil, evaluate the fal form. Bindings have the same syntax as the let macro.Community Examples
(if-not condition then &opt else) Shorthand for (if (not condition) else then).Community Examples
(if-with [binding ctor dtor] truthy &opt falsey) Similar to with, but if binding is false or nil, evaluates the falsey path. Otherwise, evaluates the truthy path. In both cases, ctor is bound to binding.Community Examples
(import path & args) Import a module. First requires the module, and then merges its symbols into the current environment, prepending a given prefix as needed. (use the :as or :prefix option to set a prefix). If no prefix is provided, use the name of the module as a prefix. One can also use :export true to re-export the imported symbols. If :exit true is given as an argument, any errors encountered at the top level in the module will cause (os/exit 1) to be called. Dynamic bindings will NOT be imported. Use :fresh to bypass the module cache.Community Examples
(import* path & args) Function form of import. Same parameters, but the path and other symbol parameters should be strings instead.Community Examples
(in ds key &opt dflt) Get value in ds at key, works on associative data structures. Arrays, tuples, tables, structs, strings, symbols, and buffers are all associative and can be used. Arrays, tuples, strings, buffers, and symbols must use integer keys that are in bounds or an error is raised. Structs and tables can take any value as a key except nil and will return nil or dflt if not found.Community Examples
(index-of x ind &opt dflt) Find the first key associated with a value x in a data structure, acting like a reverse lookup. Will not look at table prototypes. Returns dflt if not found.Community Examples
(int/s64 value) Create a boxed signed 64 bit integer from a string value.Community Examples
(int/u64 value) Create a boxed unsigned 64 bit integer from a string value.Community Examples
(int? x) Check if x can be exactly represented as a 32 bit signed two's complement integer.Community Examples
(interleave & cols) Returns an array of the first elements of each col, then the second, etc.Community Examples
(interpose sep ind) Returns a sequence of the elements of ind separated by sep. Returns a new array.Community Examples
(invert ds) Returns a table where the keys of an associative data structure are the values, and the values are the keys. If multiple keys in `ds` are mapped to the same value, only one of those values will become a key in the returned table.Community Examples
The flag set of config options from janetconf.h which is used to check if native modules are compatible with the host program.Community Examples
(juxt & funs) Macro form of juxt*. Same behavior but more efficient.Community Examples
(juxt* & funs) Returns the juxtaposition of functions. In other words, ((juxt* a b c) x) evaluates to [(a x) (b x) (c x)].Community Examples
(keep pred ind) Given a predicate `pred`, return a new array containing the truthy results of applying `pred` to each element in the indexed collection `ind`. This is different from `filter` which returns an array of the original elements where the predicate is truthy.Community Examples
(keyword & xs) Creates a keyword by concatenating the elements of `xs` together. If an element is not a byte sequence, it is converted to bytes via `describe`. Returns the new keyword.Community Examples
(keyword/slice bytes &opt start end) Same a string/slice, but returns a keyword.Community Examples
(kvs dict) Takes a table or struct and returns and array of key value pairs like @[k v k v ...]. Returns a new array.Community Examples
(label name & body) Set a label point that is lexically scoped. Name should be a symbol that will be bound to the label.Community Examples
(last xs) Get the last element from an indexed data structure.Community Examples
(length ds) Returns the length or count of a data structure in constant time as an integer. For structs and tables, returns the number of key-value pairs in the data structure.Community Examples
(let bindings & body) Create a scope and bind values to symbols. Each pair in bindings is assigned as if with def, and the body of the let form returns the last value.Community Examples
(load-image image) The inverse operation to make-image. Returns an environment.Community Examples
A table used in combination with unmarshal to unmarshal byte sequences created by make-image, such that (load-image bytes) is the same as (unmarshal bytes load-image-dict).Community Examples
(loop head & body) A general purpose loop macro. This macro is similar to the Common Lisp loop macro, although intentionally much smaller in scope. The head of the loop should be a tuple that contains a sequence of either bindings or conditionals. A binding is a sequence of three values that define something to loop over. They are formatted like: binding :verb object/expression Where `binding` is a binding as passed to def, `:verb` is one of a set of keywords, and `object` is any expression. The available verbs are: * `:iterate` - repeatedly evaluate and bind to the expression while it is truthy. * `:range` - loop over a range. The object should be a two-element tuple with a start and end value, and an optional positive step. The range is half open, [start, end). * `:range-to` - same as :range, but the range is inclusive [start, end]. * `:down` - loop over a range, stepping downwards. The object should be a two-element tuple with a start and (exclusive) end value, and an optional (positive!) step size. * `:down-to` - same as :down, but the range is inclusive [start, end]. * `:keys` - iterate over the keys in a data structure. * `:pairs` - iterate over the key-value pairs as tuples in a data structure. * `:in` - iterate over the values in a data structure or fiber. `loop` also accepts conditionals to refine the looping further. Conditionals are of the form: :modifier argument where `:modifier` is one of a set of keywords, and `argument` is keyword-dependent. `:modifier` can be one of: * `:while expression` - breaks from the loop if `expression` is falsey. * `:until expression` - breaks from the loop if `expression` is truthy. * `:let bindings` - defines bindings inside the loop as passed to the `let` macro. * `:before form` - evaluates a form for a side effect before the next inner loop. * `:after form` - same as `:before`, but the side effect happens after the next inner loop. * `:repeat n` - repeats the next inner loop `n` times. lets try putting a loop item on multiple lines. * `:when condition` - only evaluates the loop body when condition is true. The `loop` macro always evaluates to nil.
# -> prints 0123456789 (not followed by newline)
(loop [x :range [0 10]]
(prin x))
# Cartesian product (nested loops)
# -> prints 00010203101112132021222330313233
# Same as (for x 0 4 (for y 0 4 (prin x y)))
(loop [x :range [0 4]
y :range [0 4]]
(prin x y))
# -> prints bytes of "hello, world" as numbers
(loop [character :in "hello, world"]
(print character))
# -> prints 1, 2, and 3, in an unspecified order
(loop [value :in {:a 1 :b 2 :c 3}]
(print value))
# -> prints 0 to 99 inclusive
(loop [x :in (range 100)]
(print x))
# Complex body
(loop [x :in (range 10)]
(print x)
(print (inc c))
(print (+ x 2)))
# Iterate over keys
(loop [k :keys {:a 1 :b 2 :c 3}]
(print k))
# print a, b, and c in an unspecified order
(loop [index :keys [:a :b :c :d]]
(print index))
# print 0, 1, 2, and 3 in order.
(defn print-pairs
[x]
(loop [[k v] :pairs x]
(printf "[%v]=%v" k v)))
(print-pairs [:a :b :c])
# [0]=:a
# [1]=:b
# [2]=:c
(print-pairs {:a 1 :b 2 :c 3})
# [:a]=1
# [:b]=2
# [:c]=3
# Some modifiers - allow early termination and conditional execution
# of the loop
(loop [x :range [0 100] :when (even? x)]
(print x))
# prints even numbers 0, 2, 4, ..., 98
(loop [x :range [1 100] :while (pos? (% x 7))]
(print x))
# prints 1, 2, 3, 4, 5, 6
# Consume fibers as generators
(def f
(fiber/new
(fn []
(for i 0 100
(yield i)))))
(loop [x :in f]
(print x))
# print 0, 1, 2, ... 99
# Modifiers in nested loops
(loop [x :range [0 10]
:after (print)
y :range [0 x]]
(prin y " "))
# 0
# 0 1
# 0 1 2
# 0 1 2 3
# 0 1 2 3 4
# 0 1 2 3 4 5
# 0 1 2 3 4 5 6
# 0 1 2 3 4 5 6 7
# 0 1 2 3 4 5 6 7 8
Community Examples(macex x &opt on-binding) Expand macros completely. on-binding is an optional callback whenever a normal symbolic binding is encounter. This allows macros to easily see all bindings use by their arguments by calling macex on their contents. The binding itself is also replaced by the value returned by on-binding within the expand macro.Community Examples
(macex1 x &opt on-binding) Expand macros in a form, but do not recursively expand macros. See `macex` docs for info on on-binding.Community Examples
(maclintf level fmt & args) When inside a macro, call this function to add a linter warning. Takes a `fmt` argument like `string/format` which is used to format the message.Community Examples
(make-env &opt parent) Create a new environment table. The new environment will inherit bindings from the parent environment, but new bindings will not pollute the parent environment.Community Examples
(make-image env) Create an image from an environment returned by require. Returns the image source as a string.Community Examples
A table used in combination with marshal to marshal code (images), such that (make-image x) is the same as (marshal x make-image-dict).Community Examples
(map f & inds) Map a function over every value in a data structure and return an array of the results.Community Examples
(mapcat f ind) Map a function over every element in an array or tuple and use array to concatenate the results.Community Examples
(marshal x &opt reverse-lookup buffer) Marshal a value into a buffer and return the buffer. The buffer can then later be unmarshalled to reconstruct the initial value. Optionally, one can pass in a reverse lookup table to not marshal aliased values that are found in the table. Then a forward lookup table can be used to recover the original value when unmarshalling.Community Examples
(match x & cases) Pattern matching. Match an expression `x` against any number of cases. Each case is a pattern to match against, followed by an expression to evaluate to if that case is matched. Legal patterns are: * symbol -- a pattern that is a symbol will match anything, binding `x`'s value to that symbol. * array -- an array will match only if all of its elements match the corresponding elements in `x`. * table or struct -- a table or struct will match if all values match with the corresponding values in `x`. * tuple -- a tuple pattern will match if its first element matches, and the following elements are treated as predicates and are true. * `\_` symbol -- the last special case is the `\_` symbol, which is a wildcard that will match any value without creating a binding. While a symbol pattern will ordinarily match any value, the pattern `(@ <sym>)`, where <sym> is any symbol, will attempt to match `x` against a value already bound to `<sym>`, rather than matching and rebinding it. Any other value pattern will only match if it is equal to `x`.Community Examples
(math/atan2 y x) Returns the arctangent of y/x. Works even when x is 0.Community Examples
(math/atanh x) Returns the hyperbolic arctangent of x.Community Examples
(math/ceil x) Returns the smallest integer value number that is not less than x.Community Examples
(math/erfc x) Returns the complementary error function of x.Community Examples
(math/floor x) Returns the largest integer value number that is not greater than x.Community Examples
(math/hypot a b) Returns c from the equation c^2 = a^2 + b^2.Community Examples
The maximum contiguous integer represtenable by a double (-(2^53))Community Examples
The minimum contiguous integer representable by a double (2^53)Community Examples
The maximum contiguous integer represtenable by a 32 bit signed integerCommunity Examples
The minimum contiguous integer representable by a 32 bit signed integerCommunity Examples
(math/log1p x) Returns (log base e of x) + 1 more accurately than (+ (math/log x) 1)Community Examples
(math/next x y) Returns the next representable floating point vaue after x in the direction of y.Community Examples
(math/random) Returns a uniformly distributed random number between 0 and 1Community Examples
(math/rng &opt seed) Creates a Psuedo-Random number generator, with an optional seed. The seed should be an unsigned 32 bit integer or a buffer. Do not use this for cryptography. Returns a core/rng abstract type.Community Examples
(math/rng-buffer rng n &opt buf) Get n random bytes and put them in a buffer. Creates a new buffer if no buffer is provided, otherwise appends to the given buffer. Returns the buffer.Community Examples
(math/rng-int rng &opt max) Extract a random random integer in the range [0, max] from the RNG. If no max is given, the default is 2^31 - 1.Community Examples
(math/rng-uniform rng) Extract a random number in the range [0, 1) from the RNG.Community Examples
(math/seedrandom seed) Set the seed for the random number generator. seed should be an integer or a buffer.Community Examples
(math/trunc x) Returns the integer between x and 0 nearest to x.Community Examples
(merge & colls) Merges multiple tables/structs to one. If a key appears in more than one collection, then later values replace any previous ones. Returns a new table.Community Examples
(merge-into tab & colls) Merges multiple tables/structs into a table. If a key appears in more than one collection, then later values replace any previous ones. Returns the original table.Community Examples
(merge-module target source &opt prefix export) Merge a module source into the target environment with a prefix, as with the import macro. This lets users emulate the behavior of import with a custom module table. If export is truthy, then merged functions are not marked as private. Returns the modified target environment.Community Examples
(module/add-paths ext loader) Add paths to `module/paths` for a given loader such that the generated paths behave like other module types, including relative imports and syspath imports. `ext` is the file extension to associate with this module type, including the dot. `loader` is the keyword name of a loader in `module/loaders`. Returns the modified `module/paths`.Community Examples
Table mapping loaded module identifiers to their environments.Community Examples
(module/expand-path path template) Expands a path template as found in `module/paths` for `module/find`. This takes in a path (the argument to require) and a template string, to expand the path to a path that can be used for importing files. The replacements are as follows: * :all: -- the value of path verbatim * :cur: -- the current file, or (dyn :current-file) * :dir: -- the directory containing the current file * :name: -- the name component of path, with extension if given * :native: -- the extension used to load natives, .so or .dll * :sys: -- the system path, or (dyn :syspath)Community Examples
(module/find path) Try to match a module or path name from the patterns in module/paths. Returns a tuple (fullpath kind) where the kind is one of :source, :native, or :image if the module is found, otherwise a tuple with nil followed by an error message.Community Examples
A table of loading method names to loading functions. This table lets require and import load many different kinds of files as modules.Community Examples
Table mapping currently loading modules to true. Used to prevent circular dependencies.Community Examples
The list of paths to look for modules, templated for module/expand-path. Each element is a two-element tuple, containing the path template and a keyword :source, :native, or :image indicating how require should load files found at these paths. A tuple can also contain a third element, specifying a filter that prevents module/find from searching that path template if the filter doesn't match the input path. The filter can be a string or a predicate function, and is often a file extension, including the period.Community Examples
(nat? x) Check if x can be exactly represented as a non-negative 32 bit signed two's complement integer.Community Examples
(native path &opt env) Load a native module from the given path. The path must be an absolute or relative path on the file system, and is usually a .so file on Unix systems, and a .dll file on Windows. Returns an environment table that contains functions and other values from the native module.Community Examples
(net/accept stream &opt timeout) Get the next connection on a server stream. This would usually be called in a loop in a dedicated fiber. Takes an optional timeout in seconds, after which will return nil. Returns a new duplex stream which represents a connection to the client.Community Examples
(net/accept-loop stream handler) Shorthand for running a server stream that will continuously accept new connections. Blocks the current fiber until the stream is closed, and will return the stream.Community Examples
(net/address host port &opt type) Look up the connection information for a given hostname, port, and connection type. Returns a handle that can be used to send datagrams over network without establishing a connection. On Posix platforms, you can use :unix for host to connect to a unix domain socket, where the name is given in the port argument. On Linux, abstract unix domain sockets are specified with a leading '@' character in port.Community Examples
(net/chunk stream nbytes &opt buf timeout) Same a net/read, but will wait for all n bytes to arrive rather than return early. Takes an optional timeout in seconds, after which will return nil.Community Examples
(net/connect host port &opt type) Open a connection to communicate with a server. Returns a duplex stream that can be used to communicate with the server. Type is an optional keyword to specify a connection type, either :stream or :datagram. The default is :stream.Community Examples
(net/flush stream) Make sure that a stream is not buffering any data. This temporarily disables Nagle's algorithm. Use this to make sure data is sent without delay. Returns stream.Community Examples
(net/listen host port &opt type) Creates a server. Returns a new stream that is neither readable nor writeable. Use net/accept or net/accept-loop be to handle connections and start the server. The type parameter specifies the type of network connection, either a :stream (usually tcp), or :datagram (usually udp). If not specified, the default is :stream. The host and port arguments are the same as in net/address.Community Examples
(net/read stream nbytes &opt buf timeout) Read up to n bytes from a stream, suspending the current fiber until the bytes are available. `n` can also be the keyword `:all` to read into the buffer until end of stream. If less than n bytes are available (and more than 0), will push those bytes and return early. Takes an optional timeout in seconds, after which will return nil. Returns a buffer with up to n more bytes in it, or raises an error if the read failed.Community Examples
(net/recv-from stream nbytes buf &opt timoeut) Receives data from a server stream and puts it into a buffer. Returns the socket-address the packet came from. Takes an optional timeout in seconds, after which will return nil.Community Examples
(net/send-to stream dest data &opt timeout) Writes a datagram to a server stream. dest is a the destination address of the packet. Takes an optional timeout in seconds, after which will return nil. Returns stream.Community Examples
(net/server host port &opt handler type) Start a server asynchronously with net/listen and net/accept-loop. Returns the new server stream.Community Examples
(net/shutdown stream &opt mode) Stop communication on this socket in a graceful manner, either in both directions or just reading/writing from the stream. The `mode` parameter controls which communication to stop on the socket. * `:wr` is the default and prevents both reading new data from the socket and writing new data to the socket. * `:r` disables reading new data from the socket. * `:w` disable writing data to the socket. Returns the original socket.Community Examples
(net/write stream data &opt timeout) Write data to a stream, suspending the current fiber until the write completes. Takes an optional timeout in seconds, after which will return nil. Returns nil, or raises an error if the write failed.Community Examples
(next ds &opt key) Gets the next key in a data structure. Can be used to iterate through the keys of a data structure in an unspecified order. Keys are guaranteed to be seen only once per iteration if they data structure is not mutated during iteration. If key is nil, next returns the first key. If next returns nil, there are no more keys to iterate through.Community Examples
(not= & xs) Check if any values in xs are not equal. Returns a boolean.Community Examples
(or & forms) Evaluates to the last argument if all preceding elements are falsey, otherwise evaluates to the first truthy element.Community Examples
(os/arch) Check the ISA that janet was compiled for. Returns one of: * :x86 * :x86-64 * :arm * :aarch64 * :sparc * :wasm * :unknownCommunity Examples
(os/cd path) Change current directory to path. Returns nil on success, errors on failure.Community Examples
(os/chmod path mode) Change file permissions, where mode is a permission string as returned by os/perm-string, or an integer as returned by os/perm-int. When mode is an integer, it is interpreted as a Unix permission value, best specified in octal, like 8r666 or 8r400. Windows will not differentiate between user, group, and other permissions, and thus will combine all of these permissions. Returns nil.Community Examples
(os/clock) Return the number of whole + fractional seconds since some fixed point in time. The clock is guaranteed to be non decreasing in real time.Community Examples
(os/cryptorand n &opt buf) Get or append n bytes of good quality random data provided by the OS. Returns a new buffer or buf.Community Examples
(os/date &opt time local) Returns the given time as a date struct, or the current time if `time` is not given. Returns a struct with following key values. Note that all numbers are 0-indexed. Date is given in UTC unless `local` is truthy, in which case the date is formatted for the local timezone. * :seconds - number of seconds [0-61] * :minutes - number of minutes [0-59] * :hours - number of hours [0-23] * :month-day - day of month [0-30] * :month - month of year [0, 11] * :year - years since year 0 (e.g. 2019) * :week-day - day of the week [0-6] * :year-day - day of the year [0-365] * :dst - if Day Light Savings is in effectCommunity Examples
(os/dir dir &opt array) Iterate over files and subdirectories in a directory. Returns an array of paths parts, with only the file name or directory name and no prefix.Community Examples
(os/execute args &opt flags env) Execute a program on the system and pass it string arguments. `flags` is a keyword that modifies how the program will execute. * :e - enables passing an environment to the program. Without :e, the current environment is inherited. * :p - allows searching the current PATH for the binary to execute. Without this flag, binaries must use absolute paths. * :x - raise error if exit code is non-zero. * :d - Don't try and terminate the process on garbage collection (allow spawning zombies). `env` is a table or struct mapping environment variables to values. It can also contain the keys :in, :out, and :err, which allow redirecting stdio in the subprocess. These arguments should be core/file values. One can also pass in the :pipe keyword for these arguments to create files that will read (for :err and :out) or write (for :in) to the file descriptor of the subprocess. This is only useful in `os/spawn`, which takes the same parameters as `os/execute`, but will return an object that contains references to these files via (return-value :in), (return-value :out), and (return-value :err). Returns the exit status of the program.Community Examples
(os/exit &opt x) Exit from janet with an exit code equal to x. If x is not an integer, the exit with status equal the hash of x.Community Examples
(os/getenv variable &opt dflt) Get the string value of an environment variable.Community Examples
(os/link oldpath newpath &opt symlink) Create a link at newpath that points to oldpath and returns nil. Iff symlink is truthy, creates a symlink. Iff symlink is falsey or not provided, creates a hard link. Does not work on Windows.Community Examples
(os/lstat path &opt tab|key) Like os/stat, but don't follow symlinks.Community Examples
(os/mkdir path) Create a new directory. The path will be relative to the current directory if relative, otherwise it will be an absolute path. Returns true if the directory was created, false if the directory already exists, and errors otherwise.Community Examples
(os/mktime date-struct &opt local) Get the broken down date-struct time expressed as the number of seconds since January 1, 1970, the Unix epoch. Returns a real number. Date is given in UTC unless local is truthy, in which case the date is computed for the local timezone. Inverse function to os/date.Community Examples
(os/open path &opt flags mode) Create a stream from a file, like the POSIX open system call. Returns a new stream. mode should be a file mode as passed to os/chmod, but only if the create flag is given. The default mode is 8r666. Allowed flags are as follows: * :r - open this file for reading * :w - open this file for writing * :c - create a new file (O_CREATE) * :e - fail if the file exists (O_EXCL) * :t - shorten an existing file to length 0 (O_TRUNC) Posix only flags: * :a - append to a file (O_APPEND) * :x - O_SYNC * :C - O_NOCTTY Windows only flags: * :R - share reads (FILE_SHARE_READ) * :W - share writes (FILE_SHARE_WRITE) * :D - share deletes (FILE_SHARE_DELETE) * :H - FILE_ATTRIBUTE_HIDDEN * :O - FILE_ATTRIBUTE_READONLY * :F - FILE_ATTRIBUTE_OFFLINE * :T - FILE_ATTRIBUTE_TEMPORARY * :d - FILE_FLAG_DELETE_ON_CLOSE * :b - FILE_FLAG_NO_BUFFERINGCommunity Examples
(os/perm-int bytes) Parse a 9 character permission string and return an integer that can be used by chmod.Community Examples
(os/perm-string int) Convert a Unix octal permission value from a permission integer as returned by os/stat to a human readable string, that follows the formatting of unix tools like ls. Returns the string as a 9 character string of r, w, x and - characters. Does not include the file/directory/symlink character as rendered by `ls`.Community Examples
(os/pipe) Create a readable stream and a writable stream that are connected. Returns a two element tuple where the first element is a readable stream and the second element is the writable stream.Community Examples
(os/proc-close proc) Wait on a process if it has not been waited on, and close pipes created by `os/spawn` if they have not been closed. Returns nil.Community Examples
(os/proc-kill proc &opt wait) Kill a subprocess by sending SIGKILL to it on posix systems, or by closing the process handle on windows. If wait is truthy, will wait for the process to finsih and returns the exit code. Otherwise, returns proc.Community Examples
(os/proc-wait proc) Block until the subprocess completes. Returns the subprocess return code.Community Examples
(os/readlink path) Read the contents of a symbolic link. Does not work on Windows.Community Examples
(os/realpath path) Get the absolute path for a given path, following ../, ./, and symlinks. Returns an absolute path as a string. Will raise an error on Windows.Community Examples
(os/rename oldname newname) Rename a file on disk to a new path. Returns nil.Community Examples
(os/rmdir path) Delete a directory. The directory must be empty to succeed.Community Examples
(os/setenv variable value) Set an environment variable.Community Examples
(os/shell str) Pass a command string str directly to the system shell.Community Examples
(os/sleep n) Suspend the program for n seconds. 'nsec' can be a real number. Returns nil.Community Examples
(os/spawn args &opt flags env) Execute a program on the system and return a handle to the process. Otherwise, the same arguments as os/execute. Does not wait for the process.Community Examples
(os/stat path &opt tab|key) Gets information about a file or directory. Returns a table if the second argument is a keyword, returns only that information from stat. If the file or directory does not exist, returns nil. The keys are: * :dev - the device that the file is on * :mode - the type of file, one of :file, :directory, :block, :character, :fifo, :socket, :link, or :other * :int-permissions - A Unix permission integer like 8r744 * :permissions - A Unix permission string like "rwxr--r--" * :uid - File uid * :gid - File gid * :nlink - number of links to file * :rdev - Real device of file. 0 on windows. * :size - size of file in bytes * :blocks - number of blocks in file. 0 on windows * :blocksize - size of blocks in file. 0 on windows * :accessed - timestamp when file last accessed * :changed - timestamp when file last changed (permissions changed) * :modified - timestamp when file last modified (content changed)Community Examples
(os/symlink oldpath newpath) Create a symlink from oldpath to newpath, returning nil. Same as (os/link oldpath newpath true).Community Examples
(os/time) Get the current time expressed as the number of whole seconds since January 1, 1970, the Unix epoch. Returns a real number.Community Examples
(os/touch path &opt actime modtime) Update the access time and modification times for a file. By default, sets times to the current time.Community Examples
(os/which) Check the current operating system. Returns one of: * :windows * :macos * :web - Web assembly (emscripten) * :linux * :freebsd * :openbsd * :netbsd * :posix - A POSIX compatible system (default) May also return a custom keyword specified at build time.Community Examples
(pairs x) Get the key-value pairs of an associative data structure.Community Examples
(parse str) Parse a string and return the first value. For complex parsing, such as for a repl with error handling, use the parser api.Community Examples
(parser/byte parser b) Input a single byte into the parser byte stream. Returns the parser.Community Examples
(parser/clone p) Creates a deep clone of a parser that is identical to the input parser. This cloned parser can be used to continue parsing from a good checkpoint if parsing later fails. Returns a new parser.Community Examples
(parser/consume parser bytes &opt index) Input bytes into the parser and parse them. Will not throw errors if there is a parse error. Starts at the byte index given by index. Returns the number of bytes read.Community Examples
(parser/eof parser) Indicate that the end of file was reached to the parser. This puts the parser in the :dead state.Community Examples
(parser/error parser) If the parser is in the error state, returns the message associated with that error. Otherwise, returns nil. Also flushes the parser state and parser queue, so be sure to handle everything in the queue before calling parser/error.Community Examples
(parser/flush parser) Clears the parser state and parse queue. Can be used to reset the parser if an error was encountered. Does not reset the line and column counter, so to begin parsing in a new context, create a new parser.Community Examples
(parser/has-more parser) Check if the parser has more values in the value queue.Community Examples
(parser/insert parser value) Insert a value into the parser. This means that the parser state can be manipulated in between chunks of bytes. This would allow a user to add extra elements to arrays and tuples, for example. Returns the parser.Community Examples
(parser/new) Creates and returns a new parser object. Parsers are state machines that can receive bytes, and generate a stream of values.Community Examples
(parser/produce parser &opt wrap) Dequeue the next value in the parse queue. Will return nil if no parsed values are in the queue, otherwise will dequeue the next value. If `wrap` is truthy, will return a 1-element tuple that wraps the result. This tuple can be used for source-mapping purposes.Community Examples
(parser/state parser &opt key) Returns a representation of the internal state of the parser. If a key is passed, only that information about the state is returned. Allowed keys are: * :delimiters - Each byte in the string represents a nested data structure. For example, if the parser state is '(["', then the parser is in the middle of parsing a string inside of square brackets inside parentheses. Can be used to augment a REPL prompt. * :frames - Each table in the array represents a 'frame' in the parser state. Frames contain information about the start of the expression being parsed as well as the type of that expression and some type-specific information.Community Examples
(parser/status parser) Gets the current status of the parser state machine. The status will be one of: * :pending - a value is being parsed. * :error - a parsing error was encountered. * :root - the parser can either read more values or safely terminate.Community Examples
(parser/where parser &opt line col) Returns the current line number and column of the parser's internal state. If line is provided, the current line number of the parser is first set to that value. If column is also provided, the current column number of the parser is also first set to that value.Community Examples
(partition n ind) Partition an indexed data structure into tuples of size n. Returns a new array.Community Examples
(partition-by f ind) Partition elements of a sequential data structure by a representative function `f`. Partitions split when `(f x)` changes values when iterating to the next element `x` of `ind`. Returns a new array of arrays.Community Examples
(peg/compile peg) Compiles a peg source data structure into a <core/peg>. This will speed up matching if the same peg will be used multiple times. Will also use `(dyn :peg-grammar)` to suppliment the grammar of the peg for otherwise undefined peg keywords.Community Examples
(peg/find peg text &opt start & args) Find first index where the peg matches in text. Returns an integer, or nil if not found.Community Examples
(peg/find-all peg text &opt start & args) Find all indexes where the peg matches in text. Returns an array of integers.Community Examples
(peg/match peg text &opt start & args) Match a Parsing Expression Grammar to a byte string and return an array of captured values. Returns nil if text does not match the language defined by peg. The syntax of PEGs is documented on the Janet website.Community Examples
(peg/replace peg repl text &opt start & args) Replace first match of peg in text with repl, returning a new buffer. The peg does not need to make captures to do replacement. If no matches are found, returns the input string in a new buffer.Community Examples
(peg/replace-all peg repl text &opt start & args) Replace all matches of peg in text with repl, returning a new buffer. The peg does not need to make captures to do replacement.Community Examples
(postwalk f form) Do a post-order traversal of a data structure and call (f x) on every visitation.Community Examples
(pp x) Pretty print to stdout or (dyn :out). The format string used is (dyn :pretty-format "%q").Community Examples
(prewalk f form) Similar to postwalk, but do pre-order traversal.Community Examples
(prin & xs) Same as print, but does not add trailing newline.Community Examples
(print & xs) Print values to the console (standard out). Value are converted to strings if they are not already. After printing all values, a newline character is printed. Use the value of (dyn :out stdout) to determine what to push characters to. Expects (dyn :out stdout) to be either a core/file or a buffer. Returns nil.Community Examples
(printf fmt & xs) Prints output formatted as if with (string/format fmt ;xs) to (dyn :out stdout) with a trailing newline.Community Examples
(product xs) Returns the product of xs. If xs is empty, returns 1.
(product []) # -> 1
(product @[1 2 3]) # -> 6
(product [0 1 2 3]) # -> 0
(product (range 1 10)) # -> 362880
# Product over byte values [0-255] in a string
(product "hello") # -> 1.35996e+10
# Product over values in a table or struct
(sum {:a 1 :b 2 :c 4}) # -> 8
Community Examples(prompt tag & body) Set up a checkpoint that can be returned to. Tag should be a value that is used in a return statement, like a keyword.Community Examples
(propagate x fiber) Propagate a signal from a fiber to the current fiber. The resulting stack trace from the current fiber will include frames from fiber. If fiber is in a state that can be resumed, resuming the current fiber will first resume fiber. This function can be used to re-raise an error without losing the original stack trace.Community Examples
(protect & body) Evaluate expressions, while capturing any errors. Evaluates to a tuple of two elements. The first element is true if successful, false if an error, and the second is the return value or error.Community Examples
(put ds key value) Associate a key with a value in any mutable associative data structure. Indexed data structures (arrays and buffers) only accept non-negative integer keys, and will expand if an out of bounds value is provided. In an array, extra space will be filled with nils, and in a buffer, extra space will be filled with 0 bytes. In a table, putting a key that is contained in the table prototype will hide the association defined by the prototype, but will not mutate the prototype table. Putting a value nil into a table will remove the key from the table. Returns the data structure ds.Community Examples
(put-in ds ks v) Put a value into a nested data structure. Looks into the data structure via a sequence of keys. Missing data structures will be replaced with tables. Returns the modified, original data structure.Community Examples
(quit &opt value) Tries to exit from the current repl or context. Does not always exit the application. Works by setting the :exit dynamic binding to true. Passing a non-nil value here will cause the outer run-context to return that value.Community Examples
(range & args) Create an array of values [start, end) with a given step. With one argument returns a range [0, end). With two arguments, returns a range [start, end). With three, returns a range with optional step size.
(range 10) # -> @[0 1 2 3 4 6 7 8 9]
(range 5 10) # -> @[5 6 7 8 9]
(range 5 10 2) # -> @[5 7 9]
(range 5 11 2) # -> @[5 7 9]
(range 10 0 -1) # -> @[10 9 8 7 6 5 4 3 2 1]
Community Examples(reduce f init ind) Reduce, also know as fold-left in many languages, transforms an indexed type (array, tuple) with a function to produce a value by applying f to each element in order. f is a function of 2 arguments, (f accum el), where accum is the initial value and el is the next value in the indexed type ind. f returns a value that will be used as accum in the next call to f. reduce returns the value of the final call to f.Community Examples
(reduce2 f ind) The 2-argument version of reduce that does not take an initialization value. Instead, the first element of the array is used for initialization.Community Examples
(repeat n & body) Evaluate body n times. If n is negative, body will be evaluated 0 times. Evaluates to nil.Community Examples
(repl &opt chunks onsignal env parser read) Run a repl. The first parameter is an optional function to call to get a chunk of source code that should return nil for end of file. The second parameter is a function that is called when a signal is caught. One can provide an optional environment table to run the repl in, as well as an optional parser or read function to pass to `run-context.`Community Examples
(require path & args) Require a module with the given name. Will search all of the paths in module/paths. Returns the new environment returned from compiling and running the file.Community Examples
(resume fiber &opt x) Resume a new or suspended fiber and optionally pass in a value to the fiber that will be returned to the last yield in the case of a pending fiber, or the argument to the dispatch function in the case of a new fiber. Returns either the return result of the fiber's dispatch function, or the value from the next yield call in fiber.Community Examples
(reverse t) Reverses the order of the elements in a given array or tuple and returns a new array. If string or buffer is provided function returns array of chars reversed.
(reverse [1 2 3]) # -> @[3 2 1]
(reverse "abcdef") # -> @[102 101 100 99 98 97]
(reverse :abc) # -> @[99 98 97]
Community Examples(reverse! t) Reverses the order of the elements in a given array or buffer and returns it mutated.Community Examples
(run-context opts) Run a context. This evaluates expressions in an environment, and encapsulates the parsing, compilation, and evaluation. Returns (in environment :exit-value environment) when complete. opts is a table or struct of options. The options are as follows: * `:chunks` - callback to read into a buffer - default is getline * `:on-parse-error` - callback when parsing fails - default is bad-parse * `:env` - the environment to compile against - default is the current env * `:source` - string path of source for better errors - default is "<anonymous>" * `:on-compile-error` - callback when compilation fails - default is bad-compile * `:on-compile-warning` - callback for any linting error - default is warn-compile * `:evaluator` - callback that executes thunks. Signature is (evaluator thunk source env where) * `:on-status` - callback when a value is evaluated - default is debug/stacktrace. * `:fiber-flags` - what flags to wrap the compilation fiber with. Default is :ia. * `:expander` - an optional function that is called on each top level form before being compiled. * `:parser` - provide a custom parser that implements the same interface as Janet's built-in parser. * `:read` - optional function to get the next form, called like `(read env source)`. Overrides all parsing.Community Examples
(scan-number str) Parse a number from a byte sequence an return that number, either and integer or a real. The number must be in the same format as numbers in janet source code. Will return nil on an invalid number.Community Examples
(seq head & body) Similar to loop, but accumulates the loop body into an array and returns that. See loop for details.
(seq [x :range [0 5]] (* 2 x)) # -> @[0 2 4 6 8]
Community Examples(short-fn arg) Shorthand for fn. Arguments are given as $n, where n is the 0-indexed argument of the function. $ is also an alias for the first (index 0) argument. The $& symbol will make the anonymous function variadic if it apears in the body of the function - it can be combined with positional arguments. Example usage: * (short-fn (+ $ $)) - A function that doubles its arguments. * (short-fn (string $0 $1)) - accepting multiple args * |(+ $ $) - use pipe reader macro for terse function literals * |(+ $&) - variadic functionsCommunity Examples
(slice x &opt start end) Extract a sub-range of an indexed data structure or byte sequence.
(slice @[1 2 3]) # -> (1 2 3) (a new array!)
(slice @[:a :b :c] 1) # -> (:b :c)
(slice [:a :b :c :d :e] 2 4) # -> (:c :d)
(slice [:a :b :d :d :e] 2 -1) # -> (:c :d :e)
(slice [:a :b :d :d :e] 2 -2) # -> (:c :d)
(slice [:a :b :d :d :e] 2 -4) # -> ()
(slice [:a :b :d :d :e] 2 -10) # -> error: range error
(slice "abcdefg" 0 2) # -> "ab"
(slice @"abcdefg" 0 2) # -> "ab"
Community Examples(slurp path) Read all data from a file with name path and then close the file.Community Examples
(some pred xs) Returns nil if all xs are false or nil, otherwise returns the result of the first truthy predicate, (pred x).Community Examples
(sort ind &opt before?) Sort `ind` in-place, and return it. Uses quick-sort and is not a stable sort. If a `before?` comparator function is provided, sorts elements using that, otherwise uses `<`.Community Examples
(sort-by f ind) Returns `ind` sorted by calling a function `f` on each element and comparing the result with `<`.Community Examples
(sorted ind &opt before?) Returns a new sorted array without modifying the old one. If a `before?` comparator function is provided, sorts elements using that, otherwise uses `<`.Community Examples
(sorted-by f ind) Returns a new sorted array that compares elements by invoking a function `f` on each element and comparing the result with `<`.Community Examples
(spit path contents &opt mode) Write contents to a file at path. Can optionally append to the file.Community Examples
(string & xs) Creates a string by concatenating the elements of `xs` together. If an element is not a byte sequence, it is converted to bytes via `describe`. Returns the new string.Community Examples
(string/ascii-lower str) Returns a new string where all bytes are replaced with the lowercase version of themselves in ASCII. Does only a very simple case check, meaning no unicode support.Community Examples
(string/ascii-upper str) Returns a new string where all bytes are replaced with the uppercase version of themselves in ASCII. Does only a very simple case check, meaning no unicode support.Community Examples
(string/bytes str) Returns an array of integers that are the byte values of the string.Community Examples
(string/check-set set str) Checks that the string str only contains bytes that appear in the string set. Returns true if all bytes in str appear in set, false if some bytes in str do not appear in set.Community Examples
(string/find patt str &opt start-index) Searches for the first instance of pattern patt in string str. Returns the index of the first character in patt if found, otherwise returns nil.Community Examples
(string/find-all patt str &opt start-index) Searches for all instances of pattern patt in string str. Returns an array of all indices of found patterns. Overlapping instances of the pattern are counted individually, meaning a byte in str may contribute to multiple found patterns.Community Examples
(string/format format & values) Similar to snprintf, but specialized for operating with Janet values. Returns a new string.Community Examples
(string/from-bytes & byte-vals) Creates a string from integer parameters with byte values. All integers will be coerced to the range of 1 byte 0-255.Community Examples
(string/has-prefix? pfx str) Tests whether str starts with pfx.Community Examples
(string/has-suffix? sfx str) Tests whether str ends with sfx.Community Examples
(string/join parts &opt sep) Joins an array of strings into one string, optionally separated by a separator string sep.Community Examples
(string/repeat bytes n) Returns a string that is n copies of bytes concatenated.Community Examples
(string/replace patt subst str) Replace the first occurrence of patt with subst in the string str. Will return the new string if patt is found, otherwise returns str.Community Examples
(string/replace-all patt subst str) Replace all instances of patt with subst in the string str. Overlapping matches will not be counted, only the first match in such a span will be replaced. Will return the new string if patt is found, otherwise returns str.Community Examples
(string/reverse str) Returns a string that is the reversed version of str.Community Examples
(string/slice bytes &opt start end) Returns a substring from a byte sequence. The substring is from index start inclusive to index end exclusive. All indexing is from 0. 'start' and 'end' can also be negative to indicate indexing from the end of the string. Note that index -1 is synonymous with index (length bytes) to allow a full negative slice range.Community Examples
(string/split delim str &opt start limit) Splits a string str with delimiter delim and returns an array of substrings. The substrings will not contain the delimiter delim. If delim is not found, the returned array will have one element. Will start searching for delim at the index start (if provided), and return up to a maximum of limit results (if provided).Community Examples
(string/trim str &opt set) Trim leading and trailing whitespace from a byte sequence. If the argument set is provided, consider only characters in set to be whitespace.Community Examples
(string/triml str &opt set) Trim leading whitespace from a byte sequence. If the argument set is provided, consider only characters in set to be whitespace.Community Examples
(string/trimr str &opt set) Trim trailing whitespace from a byte sequence. If the argument set is provided, consider only characters in set to be whitespace.Community Examples
(struct & kvs) Create a new struct from a sequence of key value pairs. kvs is a sequence k1, v1, k2, v2, k3, v3, ... If kvs has an odd number of elements, an error will be thrown. Returns the new struct.Community Examples
(sum xs) Returns the sum of xs. If xs is empty, returns 0.
(sum []) # -> 0
(sum @[1]) # -> 1
(sum (range 100)) # -> 4950
# Sum over bytes values [0-255] in a string
(sum "hello") # -> 532
# Sum over values in a table or struct
(sum {:a 1 :b 2 :c 4}) # -> 7
Community Examples(symbol & xs) Creates a symbol by concatenating the elements of `xs` together. If an element is not a byte sequence, it is converted to bytes via `describe`. Returns the new symbol.Community Examples
(symbol/slice bytes &opt start end) Same a string/slice, but returns a symbol.Community Examples
(table & kvs) Creates a new table from a variadic number of keys and values. kvs is a sequence k1, v1, k2, v2, k3, v3, ... If kvs has an odd number of elements, an error will be thrown. Returns the new table.Community Examples
(table/clear tab) Remove all key-value pairs in a table and return the modified table `tab`.Community Examples
(table/clone tab) Create a copy of a table. Updates to the new table will not change the old table, and vice versa.Community Examples
(table/getproto tab) Get the prototype table of a table. Returns nil if a table has no prototype, otherwise returns the prototype.Community Examples
(table/new capacity) Creates a new empty table with pre-allocated memory for capacity entries. This means that if one knows the number of entries going to go in a table on creation, extra memory allocation can be avoided. Returns the new table.Community Examples
(table/rawget tab key) Gets a value from a table without looking at the prototype table. If a table tab does not contain t directly, the function will return nil without checking the prototype. Returns the value in the table.Community Examples
(table/setproto tab proto) Set the prototype of a table. Returns the original table tab.Community Examples
(table/to-struct tab) Convert a table to a struct. Returns a new struct. This function does not take into account prototype tables.Community Examples
(take n ind) Take the first n elements of a fiber, indexed or bytes type. Returns a new array, tuple or string, respectively.Community Examples
(take-until pred ind) Same as `(take-while (complement pred) ind)`.Community Examples
(take-while pred ind) Given a predicate, take only elements from a fiber, indexed or bytes type that satisfy the predicate, and abort on first failure. Returns a new array, tuple or string, respectively.Community Examples
(thread/close thread) Close a thread, unblocking it and ending communication with it. Note that closing a thread is idempotent and does not cancel the thread's operation. Returns nil.Community Examples
(thread/exit &opt code) Exit from the current thread. If no more threads are running, ends the process, but otherwise does not end the current process.Community Examples
(thread/new func &opt capacity flags) Start a new thread that will start immediately. If capacity is provided, that is how many messages can be stored in the thread's mailbox before blocking senders. The capacity must be between 1 and 65535 inclusive, and defaults to 10. Can optionally provide flags to the new thread - supported flags are: * `:h` - Start a heavyweight thread. This loads the core environment by default, so may use more memory initially. Messages may compress better, though. * `:a` - Allow sending over registered abstract types to the new thread * `:c` - Send over cfunction information to the new thread (no longer supported). Returns a handle to the new thread.Community Examples
(thread/receive &opt timeout) Get a message sent to this thread. If timeout (in seconds) is provided, an error will be thrown after the timeout has elapsed but no messages are received. The default timeout is 1 second, and math/inf cam be passed to turn off the timeout.Community Examples
(thread/send thread msgi &opt timeout) Send a message to the thread. By default, the timeout is 1 second, but an optional timeout in seconds can be provided. Use math/inf for no timeout. Will throw an error if there is a problem sending the message.Community Examples
(trace func) Enable tracing on a function. Returns the function.Community Examples
(tracev x) Print a value and a description of the form that produced that value to stderr. Evaluates to x.Community Examples
(try body catch) Try something and catch errors. Body is any expression, and catch should be a form with the first element a tuple. This tuple should contain a binding for errors and an optional binding for the fiber wrapping the body. Returns the result of body if no error, or the result of catch if an error.Community Examples
(tuple & items) Creates a new tuple that contains items. Returns the new tuple.Community Examples
(tuple/brackets & xs) Creates a new bracketed tuple containing the elements xs.Community Examples
(tuple/setmap tup line column) Set the sourcemap metadata on a tuple. line and column indicate should be integers.Community Examples
(tuple/slice arrtup [,start=0 [,end=(length arrtup)]]) Take a sub sequence of an array or tuple from index start inclusive to index end exclusive. If start or end are not provided, they default to 0 and the length of arrtup respectively. 'start' and 'end' can also be negative to indicate indexing from the end of the input. Note that index -1 is synonymous with index '(length arrtup)' to allow a full negative slice range. Returns the new tuple.Community Examples
(tuple/sourcemap tup) Returns the sourcemap metadata attached to a tuple, which is another tuple (line, column).Community Examples
(tuple/type tup) Checks how the tuple was constructed. Will return the keyword :brackets if the tuple was parsed with brackets, and :parens otherwise. The two types of tuples will behave the same most of the time, but will print differently and be treated differently by the compiler.Community Examples
(type x) Returns the type of `x` as a keyword. `x` is one of: * :nil * :boolean * :number * :array * :tuple * :table * :struct * :string * :buffer * :symbol * :keyword * :function * :cfunction * :fiber or another keyword for an abstract type.
(type nil) # -> :nil
(type true) # -> :boolean
(type false) # -> :boolean
(type 1) # -> :number
(type :key) # -> :keyword
(type (int/s64 "100")) # -> :core/s64
Community Examples(unless condition & body) Shorthand for (when (not condition) ;body).Community Examples
(unmarshal buffer &opt lookup) Unmarshal a value from a buffer. An optional lookup table can be provided to allow for aliases to be resolved. Returns the value unmarshalled from the buffer.Community Examples
(untrace func) Disables tracing on a function. Returns the function.Community Examples
(update ds key func & args) Accepts a key argument and passes its associated value to a function. The key is then re-associated to the function's return value. Returns the updated data structure `ds`.Community Examples
(update-in ds ks f & args) Update a value in a nested data structure by applying f to the current value. Looks into the data structure via a sequence of keys. Missing data structures will be replaced with tables. Returns the modified, original data structure.Community Examples
(use & modules) Similar to import, but imported bindings are not prefixed with a module identifier. Can also import multiple modules in one shot.Community Examples
(values x) Get the values of an associative data structure.Community Examples
(var- name & more) Define a private var that will not be exported.Community Examples
(varfn name & body) Create a function that can be rebound. varfn has the same signature as defn, but defines functions in the environment as vars. If a var 'name' already exists in the environment, it is rebound to the new function. Returns a function.Community Examples
(walk f form) Iterate over the values in ast and apply f to them. Collect the results in a data structure. If ast is not a table, struct, array, or tuple, returns form.Community Examples
(warn-compile msg level where &opt line col) Default handler for a compile warningCommunity Examples
(when condition & body) Evaluates the body when the condition is true. Otherwise returns nil.Community Examples
(when-let bindings & body) Same as (if-let bindings (do ;body)).Community Examples
(when-with [binding ctor dtor] & body) Similar to with, but if binding is false or nil, returns nil without evaluating the body. Otherwise, the same as with.Community Examples
(with [binding ctor dtor] & body) Evaluate body with some resource, which will be automatically cleaned up if there is an error in body. binding is bound to the expression ctor, and dtor is a function or callable that is passed the binding. If no destructor (dtor) is given, will call :close on the resource.
# Print all of poetry.txt, and close the file when done,
# even when there is an error.
(with [f (file/open "poetry.txt")]
(print (:read f :all)))
Community Examples(with-dyns bindings & body) Run a block of code in a new fiber that has some dynamic bindings set. The fiber will not mask errors or signals, but the dynamic bindings will be properly unset, as dynamic bindings are fiber local.Community Examples
(with-syms syms & body) Evaluates body with each symbol in syms bound to a generated, unique symbol.Community Examples
(with-vars vars & body) Evaluates body with each var in vars temporarily bound. Similar signature to let, but each binding must be a var.Community Examples
(xprin to & xs) Print to a file or other value explicitly (no dynamic bindings). The value to print to is the first argument, and is otherwise the same as prin. Returns nil.Community Examples
(xprinf to fmt & xs) Like prinf but prints to an explicit file or value to. Returns nil.Community Examples
(xprint to & xs) Print to a file or other value explicitly (no dynamic bindings) with a trailing newline character. The value to print to is the first argument, and is otherwise the same as print. Returns nil.Community Examples
(xprintf to fmt & xs) Like printf but prints to an explicit file or value to. Returns nil.Community Examples
(yield &opt x) Yield a value to a parent fiber. When a fiber yields, its execution is paused until another thread resumes it. The fiber will then resume, and the last yield call will return the value that was passed to resume.Community Examples
(zipcoll ks vs) Creates a table from two arrays/tuples. Returns a new table.Community Examples