From 1f7231153c172500f1073ddb22ec911379f83a07 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Mon, 6 Nov 2023 18:50:35 +0100
Subject: Improved wiki and reduced readme

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 docs/wiki_src/coding/examples.md | 134 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)

(limited to 'docs/wiki_src/coding/examples.md')

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+# 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.
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