Community documentation for Janet

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"

# foo.txt is a file with contents "hello\nworld\n".
(slurp "foo.txt")  # => @"hello\nworld\n"
(string/split "\n" (slurp "foo.txt"))  # => @["hello" "world" ""]

(defn slurp-lines [path]
  (string/split "\n" (slurp path)))

(slurp-lines "foo.txt")  # => @["hello" "world" ""]

(string/join @["hello" "world" ""] "\n")  # => "hello\nworld\n"
(spit "foo2.txt" (string/join @["hello" "world" ""] "\n"))
# The contents of foo.txt and foo2.txt are now identical.

(defn spit-lines [path lines]
  (spit path (string/join lines "\n")))

(spit-lines "foo3.txt" (slurp-lines "foo.txt"))
# The contents of foo.txt and foo3.txt are now identical.

(array/pop (range 12)) # => 11

(string/repeat "moshi" 2)  # => "moshimoshi"

(string/reverse "hello") # => "olleh"

(any? [false false nil]) => nil
(any? [false false nil 1]) => 1
(any? [false false nil true]) => true

(interleave [:a :b :c] 
            [1 2 3] 
            ["x" "y" "z"])
# => @[:a 1 "x" :b 2 "y" :c 3 "z"]

# janet 1.10.1

(all pos? [1 2 3])     # => true
(all pos? [1 2 3 -4])  # => false
(all pos? [1 2 3 0])   # => false

(all (partial string/has-prefix? "a") ["aa" "ab"])       # => true
(all (partial string/has-prefix? "a") ["aa" "ab" "bb"])  # => false

(all truthy? [1 2])              # => true
(all truthy? [1 2 3])            # => true
(all truthy? [1 2 nil 3])        # => false
(all truthy? [1 false 2 nil 3])  # => false

(all (fn [x] x) [1 2])              # => 2
(all (fn [x] x) [1 2 3])            # => 3
(all (fn [x] x) [1 2 nil 3])        # => nil
(all (fn [x] x) [1 false 2 nil 3])  # => false

(ev/spawn (os/sleep 1) (print "Hard work is done!"))

# prints "Hard work is done!" after one second
# this is the easiest way to put some forms on the event loop
# but do not forget REPL is blocking, for now, so run the example with `janet -e`

(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         ]

(table ;[:a 1 :b 2 :c 3])
# => @{:a 1 :b 2 :c 3}

# foo.txt is a file with contents "hello\nworld\n".
(slurp "foo.txt")  # => @"hello\nworld\n"
(string/split "\n" (slurp "foo.txt"))  # => @["hello" "world" ""]

(defn slurp-lines [path]
  (string/split "\n" (slurp path)))

(slurp-lines "foo.txt")  # => @["hello" "world" ""]

(string/join @["hello" "world" ""] "\n")  # => "hello\nworld\n"
(spit "foo2.txt" (string/join @["hello" "world" ""] "\n"))
# The contents of foo.txt and foo2.txt are now identical.

(defn spit-lines [path lines]
  (spit path (string/join lines "\n")))

(spit-lines "foo3.txt" (slurp-lines "foo.txt"))
# The contents of foo.txt and foo3.txt are now identical.

(os/execute
  ["/usr/bin/bash" "-c" "set"]
  :e
  @{"SOME" "value"
    "OTHER" "one"})
# => 0

# execute bash and prints environment variables
# which contains SOME=value and Other=one

(spit "/tmp/hello.sh" "#!/bin/bash\necho 'Hello from Bash!'\n")
(os/chmod "/tmp/hello.sh" "rwx------")
(os/setenv "PATH" (string (os/getenv "PATH") ":/tmp"))
(os/shell "hello.sh")

(scan-number "111" 2)
# => 7