Community documentation for Janet

(range 10000) # @[0 1 2 ... 9997 9998 9999]

# By default, pp truncates. You can change its behavior:
(setdyn :pretty-format "%j") # jdn format
(setdyn :pretty-format "%m") # full printing without truncation
# For a list of all print formats: https://janet-lang.org/capi/writing-c-functions.html#Panicking

(range 10000) # Prints all of them according to your dyn

(map math/abs   [-2.9 -2.1 2.1 2.9])  # => @[ 2.9  2.1  2.1  2.9 ]
(map math/floor [-2.9 -2.1 2.1 2.9])  # => @[ -3   -3   2    2   ]
(map math/ceil  [-2.9 -2.1 2.1 2.9])  # => @[ -2   -2   3    3   ]
(map math/round [-2.9 -2.1 2.1 2.9])  # => @[ -3   -2   2    3   ]
(map math/trunc [-2.9 -2.1 2.1 2.9])  # => @[ -2   -2   2    2   ]

(peg/find ':a "Battery temperature: 40 °C")

# => 0 index of the first upper/lower case character

# :a (range "az" "AZ")

# janet 1.10.1

(array/remove @[1 2 3] 0)  # => @[2 3]
(array/remove @[1 2 3] 1)  # => @[1 3]
(array/remove @[1 2 3] 2)  # => @[1 2]
(array/remove @[1 2 3] 3)  # => @[1 2 3]
(array/remove @[1 2 3] 4)  # error: index out of range

(array/remove @[1 2 3] -1)  # => @[1 2 3]
(array/remove @[1 2 3] -2)  # => @[1 2]
(array/remove @[1 2 3] -3)  # => @[1 3]
(array/remove @[1 2 3] -4)  # => @[2 3]
(array/remove @[1 2 3] -5)  # error: index out of range

(array/remove @[1 2 3 4] 1 1)   # => @[1 3 4]
(array/remove @[1 2 3 4] 1 2)   # => @[1 4]
(array/remove @[1 2 3 4] 1 3)   # => @[1]
(array/remove @[1 2 3 4] 1 4)   # => @[1]
(array/remove @[1 2 3 4] 1 99)  # => @[1]

# Janet v1.42.0 -- See %src/include/janet.h.
(defn set? [position] (["not set" "set"] (band janet/config-bits position)))
(printf ```
Configurations:
* NANBOX %s.
* SINGLE_THREADED %s.
* NANBOX_64_POINTER_SHIFT %s.``` (set? 0x1) (set? 0x2) (set? 0x4))

# janet 1.10.1

# note that os/cd does not appear to update PWD in the shell's environment.
(os/cwd)           # => "/Users/cell/tmp"
(os/getenv "PWD")  # => "/Users/cell/tmp"
(os/cd "/tmp")     # => nil
(os/cwd)           # => "/private/tmp"  (on Apple, /tmp is actually /private/tmp)
(os/getenv "PWD")  # => "/Users/cell/tmp"

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

(import joy)

# given a handler
(defn handle-func [request]
  (joy/text/plain (string "Hi " ((request :params) :name))))

# joy/routes will make handlers
(def r (joy/routes [:get "/hi/:name" :handle-func]))
# which you can pass to joy/app
(joy/server (joy/app {:routes r}) 9002)
# visit at localhost:9002/hi/bob

(peg/replace-all '(set "aiou") "e" "The quick brown fox jumps over the lazy dog")
# returns The qeeck brewn fex jemps ever the lezy deg

(var x 1)
(+= x 2 3 4)
# x = 10

(loop [x :range [1 10]
       :let [square (* x x)]
       :until (> square 9)
       :before (print "before")
       :after (print "after")
       :repeat 2]
  (print (string "square: " square)))

# before
# square: 1
# square: 1
# after
# before
# square: 4
# square: 4
# after
# before
# square: 9
# square: 9
# after

You can see janet datastructure values by typing:

(string/format "%q" {:a 1 :b 2}) # => {:a 1 :b 2} 

(string/find "needle"
             "hay hay hay needle hay")
# => 12

(when (def x 10)
  (string "Got value: " x))
# "Got value: 10"

(when (def x nil)
  (string "Got value: " x))
# nil

# nested iteration
(loop [a :in [100 200 300]
       b :in [1 2 3]]
   (print (+ a b)))

# 101
# 102
# 103
# 201
# 202
# 203
# 301
# 302
# 303

(import spork/misc)
(def d (misc/capout (doc misc/capout)))

d # returns:
@"\n\n    macro\n    /usr/local/lib/janet/spork/misc.janet on 
line 340, column 1\n\n    \e[97m(capout & body)\e[39m\n\n   
 Captures the standard output of the variadic \e[97mbody\e[39m
 and returns it as \n    a buffer.\n\n\n"

(reduce2     + [1 2 3])  # -> 6
(accumulate2 + [1 2 3])  # -> @[1 3 6]

(math/floor 1.1)  # => 1
(map math/floor [1.1 1.2 1.3])  # => @[1 1 1]

# foo.txt is a file with contents "hello\nworld\n".
(slurp "foo.txt")  # => @"hello\nworld\n"
(string/split "\n" (slurp "foo.txt"))  # => @["hello" "world" ""]

(defn slurp-lines [path]
  (string/split "\n" (slurp path)))

(slurp-lines "foo.txt")  # => @["hello" "world" ""]

(string/join @["hello" "world" ""] "\n")  # => "hello\nworld\n"
(spit "foo2.txt" (string/join @["hello" "world" ""] "\n"))
# The contents of foo.txt and foo2.txt are now identical.

(defn spit-lines [path lines]
  (spit path (string/join lines "\n")))

(spit-lines "foo3.txt" (slurp-lines "foo.txt"))
# The contents of foo.txt and foo3.txt are now identical.

(filter (fn [x] (> x 2)) [1 2 3 4 5])  # @[3 4 5]