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

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

(def a @[23 42])
(array/clear a)
(pp a)
# => prints @[]

(def buf-bytes 12)

(var new-buffer (buffer/new buf-bytes)) #--> @""

(buffer/push new-buffer "hello, world") #--> @"hello, world"

# slice with strings
(slice "Hello" 1)        # => "ello"
(slice "Playing" 0 -4)   # => "Play"
(slice "Playing" -4)     # => "ing"

# slice with keyword
(slice :hello 1)         # => "ello"

(map dictionary? [ 'ab   :ab   "ab"   @"ab"  [97 98]  @[97 98]  {0 97 1 98}  @{0 97 1 98}  ])
# =>            @[ false false false  false  false    false     true         true          ]

(map struct?     [ 'ab   :ab   "ab"   @"ab"  [97 98]  @[97 98]  {0 97 1 98}  @{0 97 1 98}  ])
# =>            @[ false false false  false  false    false     true         false         ]

(map table?      [ 'ab   :ab   "ab"   @"ab"  [97 98]  @[97 98]  {0 97 1 98}  @{0 97 1 98}  ])
# =>            @[ false false false  false  false    false     false        true          ]

(describe @[:a :b]) # => "<array 0x55EC375CF440>"

(string/find "a" "abcdefa" 1)
# not yet documented start ^ position
# => 6

### read a file line by line ###

(let [f (file/open "filename.txt")] # bind an open file handle to "f"
  (while true                       # loop until "break" is called
    (let [l (file/read f :line)]    # bind a line of the file to "l" 
      (if l                         
	(print l)                   # if l is truthy print l
	(break))))                  # if l is not break from loop
  (file/close f))                   # close the file handle 


# same as above but using "with"
# this means there's no need to 
# call file/close, also replace
# let with var
(with [f (file/open "filename.txt")]
      (while true
	(var l (file/read f :line))
	(if l
	  (print l)
	  (break))))

# Upgrade mutates, but I wasn't sure whether it'd matter using the pure sorted or mutative sort. So I
# did a simple test.

(import spork)
# create data before test
(def d @{:data (range 10000000 0 -1)})
(spork/test/timeit (update d :data sort)) # 4.32930135726929 seconds and 87.4 MB

(def d @{:data (range 10000000 0 -1)}) # 87.4 MB
(spork/test/timeit (update d :data sorted)) # 4.49482655525208 seconds and 167 MB

# Where did those memory numbers come from? With only the data, the Janet process 
# uses 87.4 MB. Timewise, they take the same amount of time but on starting, sorted
# prepares memory equivalent to its input. To check ram within Janet:
(def pid (os/getpid)) # => "/proc/367537/statm"
(def statm-path (string "/proc/" pid "/statm")) # => 367537
(slurp statm-path) # => @"40444 40038 710 82 0 39426 0\n"

# Collecting garbage:
(gccollect)
(slurp statm-path) # => @"20912 20503 695 82 0 19894 0\n"

(string/format "%f" (os/clock)) # => "1627746483.991000"

(def f (ev/go (coro "world"))) # coro is great for fast fiber creating
(ev/sleep 0.0001) # give ev a chance in the REPL, remove in file
(fiber/last-value f) # "world"

(neg? -42)  # => true
(map neg? [-1 0 1])  # => @[true false false]

## 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)

(def b @"")
(def v (* 1000 (math/random)))
# => 912.753 can differ for you
(xprintf b "Value reached level %f" v)
# => nil
b
# => @"Value reached level 912.752790\n"