blob: f4d0b6222dd8d4acb26e49eb132f06a01de0865a (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
# Examples
## Hello world!
Hello world using [lists](../coding/data-structures.md#lists-stdlist)
and [IO](../coding/IO.md)!
``` bruijn
:import std/List .
main ["Hello " ++ 0 ++ "!\n"]
```
``` bash
$ printf "world" | bruijn file.bruijn
Hello world!
```
## Syntax
Example functions demonstrating the syntax without usage of
[`std/`](/std/).
``` bruijn
# this is a comment
# returns ternary 1 (syntactic sugar)
get-one (+1)
# we can use the function in all functions below its definition
get-one2 get-one
# tests are similar to assertions in other languages
# they test equality using α-equivalence of reduced expressions
:test (get-one2) ((+1))
# indenting acts similarly to Haskell's where statement
get-one3 foo
bar (+1)
foo bar
# equivalent of λx.x or Haskell's id x = x
id [0]
# testing equivalent of (λx.x) (λx.λy.x) = λx.λy.x
# the numbers in the abstractions refer to arguments using
# De Bruijn indices
:test (id [[1]]) ([[1]])
# prefix function definition
!‣ [[1]]
# use prefix function '!'
# ![0] becomes ([[1]] [0]) which in turn becomes [[0]]
:test (![0]) ([[0]])
# infix function definition: flip and apply arguments
…<>… [[0 1]]
# use infix function '<>'
# [[0]] <> [[1]] becomes (([[0 1]] [[0]]) [[1]])
:test ([[0]] <> [[1]]) ([[1]] [[0]])
# multiple arguments
number-set set-of-three (+1) (+2) (+3)
set-of-three [[[[0 1 2 3]]]]
access-first [0 [[[0]]]]
:test (access-first number-set) ((+1))
# ignore stdin and return string
main ["Hello world!\n"]
```
## Standard library
``` bruijn
:import std/Combinator .
:import std/List .
:import std/Logic .
:import std/Number .
:import std/Option .
:import std/Pair .
# pairs with some values
love pair me you
me [[[1]]]
you [[[2]]]
:test (fst love) ([[[1]]])
:test (snd love) ([[[2]]])
# you can also write (me : you) instead of (pair me you)
# also ^love and ~love instead of (fst love) and (snd love)
# numerical operations
# remember that every mixfix chain is left-associative
five --((+8) + (-4) - (-2))
not-five? [if (0 =? (+5)) false true]
# awesome mixfix functions
:test (∑ (+1) → (+3) | [++0]) ((+9))
:test (∏ (+1) → (+3) | [++0]) ((+24))
:test (not-five? five) (false)
:test ((uncurry mul (pair (+3) (+2))) =? (+6)) (true)
# lazy evaluation using infinite lists and indexing
pow2 …!!… (iterate (…⋅… (+2)) (+1))
:test ((pow2 (+5)) =? (+32)) (true)
# options
:test (map inc (some (+1))) (some (+2))
:test (apply (some (+1)) [some ++0]) (some (+2))
# boolean
# the main function gets executed automatically
# ignore stdin arguments by not referencing 0
main [¬(false ⋀? true ⋁? true)]
:test (main [0]) (false)
```
## More examples
You can find more example programs in
[`samples/`](https://github.com/marvinborner/bruijn/tree/main/samples)
of our source-code repository. The samples include several solutions to
[Advent of Code](https://adventofcode.com/) problems.
Reading the source of the [standard library](/std/) can also be helpful.
|
