Community documentation for Janet

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

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

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

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

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

# opens a file named filename for writing, and writes Hello World!
(def f (file/open "filename" :w))
(file/write f "Hello World!")
(file/flush f)
(file/close f)

# more at https://github.com/sogaiu/margaret/tree/master/examples
(peg/match ~{:main (replace (some :header-line)
                            ,(fn [& captures]
                               (table ;captures)))
             :header-line (sequence (capture :header-name) ":"
                                    :s+
                                    (capture :header-value) :crlf)
             :header-name (to ":")
             :header-value (to :crlf)
             :crlf "\r\n"}
           (string "Content-Type: text/plain\r\n"
                   "Content-Length: 1024\r\n"))
# => @[@{"Content-Length" "1024" "Content-Type" "text/plain"}]

(os/shell "uptime")  # => 0
# printed to the console:
22:30  up 5 days,  9:31, 15 users, load averages: 1.48 1.50 1.49

(def p1 (os/spawn ["echo" "hello"] :p {:out :pipe}))
(def p2 (os/spawn ["grep" "hello"] :p {:in (p1 :out)}))

(:wait p2)
# Creates a pipeline (e.g. echo hello | grep hello)

(def ast '(print novar))
(def es (compile ast))
# => @{:column 11 :line 12 :error "unknown symbol novar"} returns struct with error on invalid ast

(int/u64 42)    # => <core/u64 42>
(int/u64 42.1)  # => <core/u64 42>
(int/u64 "42")  # => <core/u64 42>

# 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"

# :as sets a /

(import /deeper/inside :prefix "" :export true)
# @{_ @{:value <cycle 0>} cat @{:private false}}
(import /deeper/inside :as "" :export true)
# @{/cat @{:private false} _ @{:value <cycle 0>} cat @{:private false}}

(math/random)  # 0.487181

# https://en.wikipedia.org/wiki/Error_function
(math/erf 1)
# => 0.842701

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

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

(defn f1 [s] (string "-" s "-"))
(defn f2 [s] (string "=" s "="))
(defn f3 [s] (string "#" s "#"))

(def f (juxt f1 f2 f3))

(f "x") # => ("-x-" "=x=" "#x#")

(math/pow 2 8)  # => 256

(sort (keys default-peg-grammar))
# => @[:A :D :H :S :W :a :a* :a+ :d :d* :d+ :h :h* :h+ :s :s* :s+ :w :w* :w+]