Community documentation for Janet

# repeat is about _side-effects_, since it returns nil.
# You'll need to use a mutable collection if you want to
# use repeat to add repeated items to a collection:
(var coll @["Y" "Z"]) #=> @["Y" "Z"]
(repeat 3 (array/push coll "A")) #=> nil
coll
# Returns:
@["Y" "Z" "A" "A" "A"]

# You can use map if the whole collection consists
# of these repetitions:
(map (fn [_] "A") (range 3))
# Returns:
@["A" "A" "A"]

(spit "/tmp/hello.sh" "#!/bin/bash\necho 'Hello from Bash!'\n")
(os/chmod "/tmp/hello.sh" "rwx------")
(os/setenv "PATH" (string (os/getenv "PATH") ":/tmp"))
(os/shell "hello.sh")

(defn- parse-timestamp
  ``Parse a date or datetime string into a unix epoch int``
  [s]
  (if (string/find " " s)
    # datetime: "yyyy-MM-dd HH:mm"
    (let [[date-part time-part] (string/split " " s)
          [y m d]               (string/split "-" date-part)
          [hh mm]               (string/split ":" time-part)]
      (os/mktime {:year         (scan-number y)
                  :month        (scan-number m)
                  :month-day    (scan-number d)
                  :hours        (scan-number hh)
                  :minutes      (scan-number mm)
                  :seconds      0}))
    # date: "yyyy-MM-dd"
    (let [[y m d] (string/split "-" s)]
      (os/mktime {:year      (scan-number y)
                  :month     (scan-number m)
                  :month-day (scan-number d)
                  :hours 0 :minutes 0 :seconds 0}))))

(seq [i :range [0 3]
      j :range [0 3]]
  [(keyword (string/format "%c" (+ 97 i)))
   j])
# => '@[(:a 0) (:a 1) (:a 2) (:b 0) (:b 1) (:b 2) (:c 0) (:c 1) (:c 2)]

(one? :dude) # => false

(or true)        # => true
(or true true)   # => true
(or true false)  # => true

(or false 1 2)  # => 1
(or false 2 1)  # => 2

(or false nil)  # => nil
(or nil false)  # => false

# note that `or` does not behave as you might expect
# when used with `apply` and `splice`:
(or 1 2 3)             # => 1
(or (splice [1 2 3]))  # => (1 2 3)
(apply or [1 2 3])     # => (if 1 1 (if 2 2 3))

(parse "[:a :b :c]") # => [:a :b :c]

(extreme < [1 2 3])  # => 1
(extreme > [1 2 3])  # => 3

(freeze @"Ho") #=> "Ho"
(freeze ["Ho"]) #=> ("Ho")
(freeze @["Ho"]) #=> ("Ho")
(freeze @{"Ho" "Ho"}) #=> {"Ho" "Ho"}

# Get all matches, similar to a global regular expression

(peg/match '(any (+ (<- :a+) 1)) "Hello, world!")
# => @["Hello" "world"]

(peg/match '(any (+ (number :d) 1)) "1A2B3C4D5")
# => @[1 2 3 4 5]

(peg/match '(any (+ (<- :a+) 1)) "12345")
# => @[]

(net/address "0.0.0.0" 80) # => <core/socket-address 0x55CABA438E90>

(net/address "0.0.0.0" 8989) # => <core/socket-address 0x55CABA439980>

(var a 0)
(assert (pos? a) "A is definitely not positive")
# error: A is definitely not positive
#  in assert [boot.janet] on line 149, column 11
#  in _thunk [repl] (tailcall) on line 3, column 1

(os/dir "./")                   # => @[]
(os/shell "touch foo bar baz")  # => nil
(os/dir "./")                   # => @["foo" "bar" "baz"]

(math/pow 2 8)  # => 256

(describe {:a 1}) # => "<struct 0x5564AF1BD6C0>"