all repos — mn @ b4266590d9b859fdda21b33116676b310858eb00

A truly minimal concatenative programming language.

docs/learn-control-flow.md

 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
 
-----
content-type: "page"
title: "Learn: Control Flow"
-----
{@ _defs_.md || 0 @}

{{m}} provides some symbols that can be used for the most common control flow statements. Unlike most programming languages, {{m}} does not differentiate between functions and statements -- control flow statements are just ordinary symbols that manipulate the main stack.

## Conditionals

The {#link-symbol||when#} symbol can be used to implement conditional statements.

For example, consider the following program:

     (
       "Unknown" (system) let 
        [uname] (uname) let
        (uname "MINGW" indexof -1 !=)
          ("Windows" (system) bind)  
        when
        (uname "Linux" indexof -1 !=)
          ("Linux" (system) bind)  
        when
        (uname "Darwin" indexof -1 !=)
          ("macOS" (system) bind)  
        when
       "The current OS is $#" (system) interpolate puts
     ) (display-os) lambda

This program defines a symbol `display-os` that execute the **uname** system command to discover the operating system and outputs a message.

## Loops

The following symbols provide ways to implement common loops:

* {#link-symbol||foreach#}
* {#link-symbol||while#}

For example, consider the following program:

     (
       (n) let
       1 (i) let
       1 (f) let
       (i n <=)
       (
         f i * (f) bind 
         i 1 + (i) bind
       ) while
       f
     ) (factorial) lambda

This program defines a symbol `factorial` that calculates the factorial of an integer iteratively using the symbol {#link-symbol||while#}.