Community documentation for Janet

(-)
# => 0

# wrap short-fn / | 
(->> 10
     (|(/ $ 2)))
# =>
5

# also wrap fn
(->> 10
     ((fn [n] (/ n 2))))
# =>
5

(peg/find-all ~(capture ,(get default-peg-grammar :d))
              "hi 0 bye 1")
# => [3 9]

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

(invert {:a 1 :b 2 :c 3})
# => @{3 :c 1 :a 2 :b}

(var a false)
(defer (set a 42) 
  (set a true)
  (error "Oh no!"))
# error: Oh no!

(pp a) # => prints 42

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

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

(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]

(/ 1 2 3)
# => 0.166667

# removes a file in the current directory
(os/rm "hello.txt")

(defmacro- =dude
 "sets any symbolic expression to the atom :what?"
 [a]
 ~(var a :what?)) # => <function =dude>

(=dude 2) # => :what?

(=dude :2) # => :what?

(=dude 2) # => :what?

(=dude "2") # => :what?

(=dude @"2") # => :what?

(=dude @[2]) # => :what?

(=dude (2)) # => :what?

(=dude [2]) # => :what?

(=dude @{2 3}) # => :what?


(doc =dude)


# =>    macro
# =>    repl on line 59, column 1
# =>
# =>    (=dude a)


# => nil


# Macro expanding the =dude macro:

(macex (=dude 2)) # => :what?

(macex1 (=dude 2)) # => :what?

# Macros have to be quoted in order to expand

(macex ~(=dude 2)) # => (var a :what?)

(macex1 ~(=dude 2)) # => (var a :what?)

(macex ~(=dude @{2 3})) # => (var a :what?)

# demo of (@ <sym>) feature
(let [content "# => label"]
  (match [:comment @{} "# => label"]
    [:comment _ (@ content)]
    :found
    nil))
# => :found

(let [p @{:a 1}
      t @{:b 2}]
  (table/setproto t p)
  [(get t :a) (table/rawget t :a)])
# => '(1 nil)

(get @"A"                      0)  # => 65 (0b01000001)
(get (buffer/bit-clear @"A" 0) 0)  # => 64 (0b01000000)
(get (buffer/bit-clear @"A" 6) 0)  # =>  1 (0b00000001)

(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