Community documentation for Janet

## Quadratic Formula

(defn qform
  "Use the quadratic formula to solve for x. Returns all real solutions."
  [a b c]
  (def det (- (* b b) (* 4 a c)))
  (def factor (/ 0.5 a))
  (cond
    (neg? det) []
    (zero? det) [(* factor (- b))]
    (let [root-det (math/sqrt det)]
        [(* factor (- (- b) root-det)) (* factor (+ (- b) root-det))])))

    (qform 1 4 3) # -> (-3 -1)

(some odd? [2 4 6 8 10])
# =>
nil

(do
  (def coll @[])
  (forv i 0 9
    (array/push coll i)
    (+= i 2))
  coll)
# => @[0 3 6]

(os/sleep 1)    # => nil
(os/sleep 0.1)  # => nil
(os/sleep 0)    # => nil

Example usage


janet:1:> (def buf @"ABCDE")
@"ABCDE"
janet:2:> (buffer/slice 0)
error: bad slot #0, expected string|symbol|keyword|buffer, got 0
  in buffer/slice
  in _thunk [repl] (tailcall) on line 2, column 1
janet:3:> (buffer/slice buf 0)
@"ABCDE"
janet:4:> (buffer/slice buf 0 1)
@"A"
janet:5:> (buffer/slice buf 0 -1)
@"ABCDE"
janet:6:> (buffer/slice buf 1 3)
@"BC"

(def b @"")
(xprin b "HOHOHO")
# => nil
b
# => "HOHOHO"

(doc doc) # works
(doc* doc) # symbol <function doc> not found
(doc* "doc") # same as (doc doc)

(defn read-from-file [file-path]
  (let [f (file/open file-path :r)
        content  (file/read f :all)]
    (file/close f)
    content))

### USAGE 

(read-from-file "/path/to/file-read-example.janet")
# => @"(defn read-from-file [file-path]\n  (let [f (file/open file-path :r)\n        content  (file/read f :all)]\n    (file/close f)\n    content))\n"

(filter identity [1 true 2 3 nil 4 false])
# => @[1 true 2 3 4]

(string/split "," "bruce,scott,tiger,woods")
# => @["bruce" "scott" "tiger" "woods"]

(filter (partial string/has-prefix? "z") (all-bindings))  # => @[zero? zipcoll]

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

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

(def time (os/time))  # => 1593838001

(os/date t)
# => {:month 6 :dst false :year-day 185 :seconds 41 :minutes 46 :week-day 6 :year 2020 :hours 4 :month-day 3}
(os/date t false)
# => {:month 6 :dst false :year-day 185 :seconds 41 :minutes 46 :week-day 6 :year 2020 :hours 4 :month-day 3}

(os/date t true)
# => {:month 6 :dst true :year-day 184 :seconds 41 :minutes 46 :week-day 5 :year 2020 :hours 23 :month-day 2}
(os/date t :local)
# => {:month 6 :dst true :year-day 184 :seconds 41 :minutes 46 :week-day 5 :year 2020 :hours 23 :month-day 2}

(var abc 123)
(= 356 (with-vars [abc 456] (- abc 100)))

(flatten [1 [2 3 [4]] 5])  # => @[1 2 3 4 5]