#!/usr/bin/env nomsu -V6.14
#
    This file defines some actions that interact with the operating system and filesystem.
    
externally (files for $path) means:
    $files = (=lua "Files.list(\$path)")
    if $files:
        $files = (List $files)
    return $files

externally (=sh $cmd) means:
    lua> ("
        local result = io.popen(\$cmd)
        local contents = result:read("*a")
        result:close()
        return contents
    ")

external $(sh> $) = $os.execute

test:
    read file "lib/os.nom"

external $(read file $filename) = $Files.read
externally [
    write to file $filename $text, to file $filename write $text
    write $text to file $filename
] all mean:
    unless ($filename != "stdin"):
        fail "Cannot write to stdin"
    
    lua> ("
        local file = io.open(\$filename, 'w')
        file:write(\$text)
        file:close()
    ")

externally (source lines of $tree) means:
    $source = ($tree.source if ($tree is syntax tree) else $tree)
    $file = (read file $source.filename)
    return
        [
            : for $ in ($file, line number at $source.start) to
                $file, line number at $source.stop
            ..: add ($file, line $)
        ], joined with "\n"

external $(spoof file $text) = $Files.spoof
external $(spoof file $filename = $text) = $Files.spoof