Community documentation for Janet

(let (sinlu (array/new 10))  # 10 element look up table.
  (for i 0 10 (put sinlu i (math/sin (* math/pi (/ i 10)))))
  (pp sinlu))

(type (fiber/new (fn [])))
# =>
:fiber

(def [pipe-r pipe-w] (os/pipe))
(:write pipe-w "hello")
(:read pipe-r 5)
# => @"hello"

# send the string "hello" into the writable stream
# part and read it back from the readable one

(def chan (ev/chan))
(def f (ev/go (coro (ev/give-supervisor :msg "Hello")) nil chan))
(pp (ev/take chan)) # => (:msg "Hello")

(var x 1)
(loop [n :range-to [1 5]]
  (*= x n))
x # => 120

(def a-tuple-1 [:number 10])
(def a-tuple-2 [:string "Hello there!"])
(defn show [what]
  (match what
    [:number n] (printf "It's a number! %d" n)
    [:string s] (printf "Here's a string: %s" s)
    _ (printf "I dunno what this is: %q" what)))

(show a-tuple-1)
(show a-tuple-2)
(show [:array @[]])

(interleave [:a :b :c] [1 2 3]) 
# => @[:a 1 :b 2 :c 3]

(interleave [:a :b :c] (range 3)) 
# => @[:a 0 :b 1 :c 2]

(interleave [:a :b :c] (range 2)) 
# => @[:a 0 :b 1]

(struct ;(interleave [:a :b :c] [1 2 3]))
# {:c 3 :a 1 :b 2}

(table ;(interleave [:a :b :c] [1 2 3]))
# @{:c 3 :a 1 :b 2}

# This turns the current REPL session (environment) with all bindings, including synced closures,
# into a loadable or compilable image.
# It is the same as e.g.: `janet -c test.janet test.jimage` after (spit "test.janet" (currenv))

 (spit "test.jimage" (make-image (curenv)))

(string/format "%f" (os/clock)) # => "1627746483.991000"

(map hash [nil true false -1 0 3.14 :a "foo" [1 2 3] {:a 1} (fn [])])
# => @[0 1 0 -1074790400 0 1244950043 -2107123988 -1254832049 -2021739803 -1395744911 53378043]

(defmacro timeit [& body]
    # generate unique symbols to use in the macro so they can't conflict with anything used in `body`
    (with-syms [$t0 $t1]
        ~(do
            (def $t0 (os/clock :monotonic :double))
            (do ,;body)
            (def $t1 (os/clock :monotonic :double))
            (- $t1 $t0))))

(def time-taken (timeit (os/sleep 0.5)))
(printf "Took %.3f seconds" time-taken)

(os/cryptorand 1)  # => @"\n"
(os/cryptorand 1)  # => @"<"
(os/cryptorand 1)  # => @"\xC0"
(os/cryptorand 1)  # => @"\x89"

(os/cryptorand 8)  # => @"\x87\x13\x99\x95\x10su\e"

(slice [:a :b :c :d])  # => (:a :b :c :d)

(slice [:a :b :c :d] 0)  # => (:a :b :c :d)
(slice [:a :b :c :d] 1)  # => (:b :c :d)
(slice [:a :b :c :d] 3)  # => (:d)
(slice [:a :b :c :d] 4)  # => ()
(slice [:a :b :c :d] 5)  # error: index out of range

(slice [:a :b :c :d] -1)  # => ()
(slice [:a :b :c :d] -2)  # => (:d)
(slice [:a :b :c :d] -4)  # => (:b :c :d)
(slice [:a :b :c :d] -5)  # => (:a :b :c :d)
(slice [:a :b :c :d] -6)  # error: index out of range

(slice [:a :b :c :d] 0 0)  # => ()
(slice [:a :b :c :d] 0 1)  # => (:a)
(slice [:a :b :c :d] 0 4)  # => (:a :b :c :d)

(slice [:a :b :c :d] -1 -1)  # => ()
(slice [:a :b :c :d] -2 -1)  # => (:d)
(slice [:a :b :c :d] -5 -1)  # => (:a :b :c :d)

(slice [:a :b :c :d] 1 0)  # => ()
(slice [:a :b :c :d] 4 0)  # => ()
(slice [:a :b :c :d] -1 -2)  # => ()
(slice [:a :b :c :d] -1 -5)  # => ()

(var x 12) # => 12

(/= x 2) # => 6

(defn ls-sockets
  "List the sockets in the current directory."
  []
  (filter
    (fn [fname] (= :socket (os/stat fname :mode)))
    (os/dir ".")))

path/delim # => ":" on Unix and Linux, ";" on Windows

#!/usr/bin/env janet
# echo stdin to stdout.
(file/write stdout (file/read stdin :all))

## Quadratic Formula

(defn qform
  "Use the quadratic formula to solve for x. Returns all real solutions."
  [a b c]
  (def det (- (* b b) (* 4 a c)))
  (def factor (/ 0.5 a))
  (cond
    (neg? det) []
    (zero? det) [(* factor (- b))]
    (let [root-det (math/sqrt det)]
        [(* factor (- (- b) root-det)) (* factor (+ (- b) root-det))])))

    (qform 1 4 3) # -> (-3 -1)

# on a Core i5-4590:
(os/arch)  # => :x64

# on an Intel Atom N270:
(os/arch)  # => :x86

# on a raspberry pi:
(os/arch)  # => :arm

# Find all bindings (in the current environment) with "push" in the name.
(doc "push")

#    Bindings:
#
#    array/push buffer/push buffer/push-byte buffer/push-string
#    buffer/push-word
#
#    Dynamics:
#
#
#
#    Use (doc sym) for more information on a binding.