LOCO parser library MatchParser

matchparser.php

<?php

    class MatchParser extends MonoParser {
        private $first;
        private $second;

        public function __construct($internals, $first, $second, $callback = null) {
            if($internals[$first] !== $internals[$second]) {
                throw new GrammarException("Can't create a ".get_class()." first and second should be the same type");
            }
            $this->first = $first;
            $this->second = $second;
            $this->string = "new ".get_class()."(".serialiseArray($internals).")";
            parent::__construct($internals, $callback);
        }
        
        // Default callback (this should be used rarely) returns all arguments as
        // an array. In the majority of cases the user should specify a callback.
        public function defaultCallback() {
            return func_get_args();
        }
        
        public function getResult($string, $i = 0) {
            $j = $i;
            $args = array();
            foreach($this->internals as $parser) {
                $match = $parser->match($string, $j);
                $j = $match["j"];
                $args[] = $match["value"];
            }
            if($args[$this->first] !== $args[$this->second]) {
                throw new ParseFailureException("first and second don't match", $i, $string);
            }
            return array("j" => $j, "args" => $args);
        }

        // First-set is built up as follows...
        function firstSet() {
            $firstSet = array();
            foreach($this->internals as $internal) {
                // The first $internal is always in the first-set
                $firstSet[] = $internal;

                // If $internal was nullable, then the next internal in the
                // list is also in the first-set, so continue the loop.
                // Otherwise we are done.
                if(!$internal->nullable) {
                    break;
                }
            }
            return $firstSet;
        }
        
        // only nullable if everything in the list is nullable
        public function evaluateNullability() {
            foreach($this->internals as $internal) {
                if(!$internal->nullable) {
                    return false;
                }
            }
            return true;
        }
    }