Community documentation for Janet

# janet 1.10.1

(=       [1 1]   [1 1])  # => true
(=       [1 1]   [2 3])  # => false
(=       [1 1]  @[1 1])  # => false
(=       [1 1]  @[2 3])  # => false
(=      @[1 1]  @[1 1])  # => false
(=      @[1 1]  @[2 3])  # => false

(deep=   [1 1]   [1 1])  # => true
(deep=   [1 1]   [2 3])  # => false
(deep=   [1 1]  @[1 1])  # => false
(deep=   [1 1]  @[2 3])  # => false
(deep=  @[1 1]  @[1 1])  # => true
(deep=  @[1 1]  @[2 3])  # => false

(/ 2)
# => 0.5

(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

(get-in  {:a {:cc 2} :b {:dd 3}}  [:a]     42)  # => {:cc 2}
(get-in  {:a {:cc 2} :b {:dd 3}}  [:a :cc] 42)  # => 2

(get-in  {:a {:cc 2} :b {:dd 3}}  [0]  42)  # => 42
(get-in  {:a {:cc 2} :b {:dd 3}}  [:z] 42)  # => 42

(defn square [x] (* x x))
(defn square-then-dec [x] ((comp dec square) x))
(defn dec-then-square [x] ((comp square dec) x))
(square-then-dec 3)  # => 8
(dec-then-square 3)  # => 4

# Due to: https://github.com/swlkr/janetdocs/issues/50

(defn parse-date
  "Parses YYYY-MM-DD date format to time"
  [date]
  (let [[year month day] (map scan-number (string/split "-" date))]
    (os/mktime {:year year :month (dec month) :month-day (dec day)})))

(print (parse-date "2021-01-01")) # 1609459200
(print (os/strftime "%c" (parse-date "2021-01-01"))) # Fri Jan  1 00:00:00 2021

(defn array-difference [array-1 array-2]
  (filter |(not (has-value? array-2 $)) array-1))

(array-difference [1 2 3 4 5] [2 3 4]) # => @[1 5]

(map (fn [arg] (* arg arg)) (range 10))

# => @[0 1 4 9 16 25 36 49 64 81]

(<= 1 2 3) # => true
(<= 1 2 1) # => false

(put  @{:a 4 :b 5}  :c 6         )  # => @{:a 4 :b 5 :c 6}
(put  @{:a 4 :b 5}  :b nil       )  # => @{:a 4}
(put  @{:a 4 :b 5}  :z nil       )  # => @{:a 4 :b 5}

(put  @[:a :b :c]   0  :z        )  # => @[:z :b :c]
(put  @[:a :b :c]   1  nil       )  # => @[:a nil :c]

(put  @[:a :b :c]   5  :d        )  # => @[:a :b :c nil nil :d]

(put  @"hello"      0  "z"       )  # error: can only put integers in buffers
(defn ord [ch] (first (string/bytes ch)))
(ord "z")  # => 122
(put  @"hello"      0  122       )  # => @"zello"
(put  @"hello"      0  (ord "z") )  # => @"zello"
(put  @"hello"      8  (ord "y") )  # => @"hello\0\0\0y"

(eachk k [1 2 3] (print k))
# prints 0
# prints 1
# prints 2
# for indexed collections indices are printed  

(reduce string "ha" ["ha" "ha" "ha" "ha"]) # => "hahahahaha"

(accumulate string "ha" ["ha" "ha" "ha" "ha"]) # => @["haha" "hahaha" "hahahaha" "hahahahaha"]

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

(sandbox :fs) # disable access to the sandbox
(os/mkdir "lol")

# error: operation forbidden by sandbox
#   in os/mkdir [src/core/os.c] on line 2146
#   in thunk [repl] (tail call) on line 30, column 1

(os/shell "seq 12 | head -n 1") # => 1