LANGUAGE.md

Endo Language Design

This file should sketch some example syntax that we'd like to consider supporting.

This document is used to bootstrap and and formulate the idea of how the Endo's shell syntax might look like.

POSIX / Bash-style control flow

if condition; then block; else block2; fi
if condition; then block; fi
while condition; do block; done

if condition
then
    block
fi

while condition
do
    block
done

condition && block || block2
condition || block

C-style control flow

if (condition) { block } else { block2 }
while (condition) { block }

Shell Pipes

# linking processes
ps afx | grep --color $USERNAME

# linking control flow / builtin commands with processes
while read N; do echo "N: $N"; done <README.md | sort | uniq
while read N <README.md; do echo "N: $N"; done | sort | uniq

declare variables in local scope

let VAR VALUE               # define immutable local variable
let mut VAR VALUE           # define mutable local variable
let global VAR VALUE        # define global variable (regardless of current scope)

mut and global are simply modifiers (directives) and thus not reserved keywords like let.

export variables to child processes

export NAME

functions

# Define function f, receiving 3 string parameters, and returning one string
let f (a, b, c): str =
    echo "a: $a, b: $b, c: $c"
    return "($a,$b,$c)"

let y = f "foo" 3.1415 $VAR      # prints and returns something into $y
echo $y                          # prints "(foo,3.1415,VALUE)"

let g a b: str =
    echo "a is: $a, and b is: $b"
    if a = b then
        return "same"
    else
        return "not same"

let has_var name: bool =
    return (getenv $name) != ""

# single-line function definition
let has_var name: bool = (getenv $name) != ""