/**
* Load parser from a file that contains the grammar.
* Example:
* %skip space \s
*
* %token word [a-zA-Z]+
* %token number [0-9]+(\.[0-9]+)?
* %token open_par \(
* %token close_par \)
* %token equal =
* %token plus \+
* %token minus \-
* %token divide \/
* %token times \*
*
* #equation:
* formula() ::equal:: <number>
*
* formula:
* factor()
* (
* ::plus:: formula() #addition
* | ::minus:: formula() #substraction
* )?
*
* factor:
* operand()
* (
* ::times:: factor() #product
* | ::divide:: factor() #division
* )?
*
* operand:
* <word>
* | ::minus::? <number> #number
* | ::open_par:: formula() ::close_par::
*
* Use tabs or spaces, it does not matter.
* Instructions follow the form: %<instruction>. Only %skip and %token are
* supported.
* Rules follow the form: <rule name>:<new line>[<space><rule><new line>]*.
* Contexts are useful to set specific skips and tokens. We give a full
* example with context + unification (for fun) to parse <a>b</a>:
* %skip space \s
* %token lt < -> in_tag
* %token inner [^<]*
*
* %skip in_tag:space \s
* %token in_tag:slash /
* %token in_tag:tagname [^>]+
* %token in_tag:gt > -> default
*
* #foo:
* ::lt:: <tagname[0]> ::gt::
* <inner>
* ::lt:: ::slash:: ::tagname[0]:: ::gt::
*
* @param \Hoa\Stream\IStream\In $stream Stream that contains the
* grammar.
* @return \Hoa\Compiler\Llk\Parser
* @throws \Hoa\Compiler\Exception
*/
public static function load(Stream\IStream\In $stream)
{
$pp = $stream->readAll();
if (empty($pp)) {
$message = 'The grammar is empty';
if ($stream instanceof Stream\IStream\Pointable) {
if (0 < $stream->tell()) {
$message .= ': the stream ' . $stream->getStreamName() . ' is pointable and not rewinded, maybe it ' . 'could be the reason';
} else {
$message .= ': nothing to read on the stream ' . $stream->getStreamName();
}
}
throw new Compiler\Exception($message . '.', 0);
}
static::parsePP($pp, $tokens, $rawRules);
$ruleAnalyzer = new Rule\Analyzer($tokens);
$rules = $ruleAnalyzer->analyzeRules($rawRules);
return new Parser($tokens, $rules);
}
