parser.php

<?php
    $lexer = $factory->createLexer([[
        ';(?:.*)(?:\\n)?'                => 'comment',
        '#_\s?\S+'                       => 'discard',
        '[\s,]+'                         => 'whitespace',
        '\\('                            => 'list_start',
        '\\)'                            => 'list_end',
        '\\['                            => 'vector_start',
        '\\]'                            => 'vector_end',
        '#\\{'                           => 'set_start',
        '\\{'                            => 'map_start',
        '\\}'                            => 'map_set_end',

        'nil|true|false'                 => function($_, $matches) {
            static $literals = ['nil' => null, 'true' => true, 'false' => false];
            return ['literal', $literals[$matches[0]]];
        },
        '"([^"\\\\]*(?:\\\\.[^"\\\\]*)*)"' => function($_, $matches) {
            $string = strtr($matches[1], [
                '\t' => "\t",
                '\r' => "\r",
                '\n' => "\n",
                '\"' => "\"",
            ]);
            return ['string', $string];
        },
        '\\\\([a-z]+)'                   => function($_, $matches) {
            static $chars = [
                'newline' => "\n",
                'return'  => "\r",
                'space'   => ' ',
                'tab'     => "\t",
            ];

            $name = $matches[1];
            return ['character', isset($chars[$name]) ? $chars[$name] : $name];
        },
        '[+-]?[0-9]+\.[0-9]+M?'          => function($_, $matches) {
            return ['float', (float) $matches[0]];
        },
        '[+-]?[0-9]+N?'                  => function($_, $matches) {
            return ['int', (int) $matches[0]];
        },
        get_symbol_regex()               => function($_, $matches) {
            return ['symbol', Symbol::get($matches[0])];
        },
        ':('.get_symbol_regex().')'      => function($_, $matches) {
            return ['symbol', Keyword::get($matches[1])];
        },
        '#('.get_symbol_regex().')'      => function($_, $matches) {
            return ['symbol', new Tag($matches[1])];
        },
    ]]);