Community documentation for Janet

(keyword? :a)   # => true
(keyword? "a")  # => false

# many terminals will truncate long data, use this if you need to see/copypaste it:
(defn full-print `Print a large DS without truncation` [ds] (print (string/format "%m" ds)))

# When the :doc-color dynamic binding referenced by *doc-color* is truthy,
# the doc-format function replaces a minimal subset of Markdown markup with
# the corresponding ANSI escape codes.
#
# The following markup is supported:
# - *this will be underlined*
# - **this will be bold**
# - `(+ 1 2 3)` <- backticks for code
#
# You may be surprised by *underline* since the same markup is used to
# indicate italics in Markdown. This is likely a tradeoff for compatibility;
# historically, the italic attribute has not been widely supported by
# terminal emulators.
#
# The best way to see the effect of *doc-color* is try the following examples
# in the Janet REPL.

# By default, *doc-color* is enabled.
(print (doc-format "*underline*. **bold**. `(code)`."))

# Set the dynamic binding to a falsy value to disable doc-format's ANSI
# escape code substition.
(with-dyns [*doc-color* false]
  (print (doc-format "*underline*. **bold**. `(code)`.")))

# N.B.: At the time of writing, no docstrings in the core API take advantage of
# the bold or underline markup As a result, you may not see any difference in
# the doc formatting if your terminal theme uses the same hue for white and
# bright white (a few terminals that I tested on Linux make no distinction
# between the two colors in their default configuration).

# note that os/touch does not create a file if it does not yet exist.
(os/touch "foo")
error: No such file or directory
  in os/touch
  in _thunk [repl] (tailcall) on line 2, column 1

(apply * [1 2 3])     # -> 6
(* (splice [1 2 3]))  # -> 6
(* ;[1 2 3])          # -> 6
(* 1 2 3)             # -> 6

(get default-peg-grammar :h)
# => '(range "09" "af" "AF")

(def a @[1 2])
(array/concat a 3 [4 5] @[6 7] [] @[] 8)
a  # => @[1 2 3 4 5 6 7 8]

(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)  # => ()

# note, if running a server from the repl, you need to (quit) your repl.

# in a terminal:
# $ while true; do date | nc 0.0.0.0 1234 -w 1; sleep 1; done

# in a janet repl:
(net/server "0.0.0.0" 1234
  (fn [conn]
    (prin (net/read conn 4096))
    (net/close conn)))
# output doesn't actually start until you (quit) your repl's fiber:
(quit)

(as-> [1 2 3] _ 
  (map inc _)
  (sum _)
  (- _ 10)
  (< _ 0))
# -> true

# same as
(< (- (sum (map inc [1 2 3])) 10) 0)

# Run this in a file.
# Notice how each thread gets its own copy of the environment,
# including the global 'counter' variable.

(var counter 0)
(defn start-thread [name sleep]
  (def chan (ev/thread-chan))
  (ev/spawn-thread
    (repeat 10
      (ev/sleep sleep)
      (++ counter)
      (print name " counter is " counter))
    (print name " has finished")
    (ev/give chan "done"))
  chan)

# Spawn two threads that increment counter
(def chan-a (start-thread "Slow thread" 0.8))
(def chan-b (start-thread "Fast thread" 0.45))

# Wait for both threads to finish
(ev/take chan-a)
(ev/take chan-b)
(print "Global counter is still " counter)

(dec 42)  # => 41
(map dec [1 2 3])  # => @[0 1 2]

(let [c0 (ev/chan)
      c1 (ev/chan 1)]
  [(ev/capacity c0) (ev/capacity c1)])
# => '(0 1)

(buffer/bit (buffer/new-filled 1 48) 4)
# => true