Community documentation for Janet

# sorted allocates the full memory of its input

(def d2  (range 10000000 0 -1)) # 87mb
(sorted d2) # now 167 mb

(mean [1 10 100])  # => 37
(mean [])          # => nan

(distinct [1 1 2 3])  # => @[1 2 3]

(distinct "hello")  # => @[104 101 108 111]
(string/from-bytes (splice (distinct "hello")))  # => "helo"

(get (os/environ) "HOME")  # => "/Users/cell"
(os/getenv "HOME")  # => "/Users/cell"

(find-index |(= $ "b") ["a" "b" "c" "d"]) #=> 1

(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"

(take-while number? 
            (fiber/new
              |(each x [1 2 3 :hi]
                 (yield x))))
# => @[1 2 3]

(last [1 1 2 3 5 8])
# => 8

(get      [4 5 6]   -1     )  # => nil
(in       [4 5 6]   -1  42 )  # error
(get-in   [4 5 6]  [-1] 42 )  # => 42

(get     {:a 1}   -1     )  # => nil
(in      {:a 1}   -1  42 )  # => 42
(get-in  {:a 1}  [-1] 42 )  # => 42

(math/hypot 1 1)  # => 1.41421
(math/sqrt 2)     # => 1.41421

(> 12 11 10 9 8 7 6 5 4 3 2 1) # => true

(> 12 11 10 9 8 7 6 5 4 3 2 9) # => false

# due to 0 indexing, you will often want to add 1 to things:
(defn short-date [d]
  (let [{:year y :month mon :month-day d} d]
    (string y "-" (+ 1 mon) "-" (+ 1 d))))

# Makes os/date like 2025-12-25
(short-date (os//date))


# From: https://codeberg.org/veqq/deforester/src/branch/master/deforester.janet
(defn- time-string 
  ``Gives current time as ISO 8601 string: 2025-10-12T11:43:14 https://en.wikipedia.org/wiki/ISO_8601
  This accounts for `os/date` 0-indexing month and days which are 1-indexed in ISO 8601.``
  []
  (let [{:year y :month mon :month-day d :hours h :minutes min :seconds s} (os/date)]
    (string y "-" (+ 1 mon) "-" (+ 1 d) "T" h ":" min ":" s)))

(if-let [x true 
         y (not x)]
  :a
  :b)
# => :b

(math/log (* math/e math/e))  # => 2
(math/log2 256)               # => 8
(math/log10 1000)             # => 3

(chr "a")  # => 97