PHP to the rescue!! This code will read a BNF and give it back to you in
an easy-to-use associative array. Very handy if I do say so myself. Got
me through the 431 parser in only a few lines of code. Enjoy!
<?php
// This code is GPLed. Copyleft, Dave Smith, 2003 :-)
$file = file( "my_grammar.txt" );
$grammar = array();
$line_num = read_grammar( 0, $file, $grammar );
print_r( $grammar );
exit;
function read_terminal( $str ) {
preg_match( "/^([^<]+)<?/", $str, $match );
return $match[1];
}
function read_nonterminals( $str ) {
if( $str{0} != '<' ) return false;
preg_match_all( "/<[^<>]+>/", $str, $match );
return $match[0];
}
function read_nonterminal( $str ) {
preg_match( "/^(<[^>]+>)/", $str, $match );
return $match[1];
}
function read_grammar( $line_num, $file, &$grammar )
{
// build the grammar
$grammar = array();
$count = 0;
while( null != trim( $line = $file[$line_num] ) ) {
//echo "$line_num: $line";
$count++;
$line = $file[$line_num];
if( ! trim($line) ) {
break;
} else {
$rule = explode( " ::= ", trim($line) );
$term = read_terminal( $rule[1] );
$next_state =
read_nonterminal(substr($rule[1],strlen($term)));
$stack_push = read_nonterminals(substr($rule[1],
strlen($term)+strlen($next_state)));
if( ! $next_state && ! $stack_push ) {
$next_state = "<POP>";
$grammar[ "<POP>" ][ $rule[0] ] = array(
'next_state' => $rule[0], 'stack_push' => NULL );
}
$grammar[ $rule[0] ][] = array( 'next_state' =>
$next_state,
'stack_push' => $stack_push,
'input' => $term );
}
$line_num++;
}
return $count;
}
?>
On Sat, 2003-05-31 at 15:46, Lars Olson wrote:
> Anyone know of a tool to parse a large file according to a BNF
> definition? I've looked at Parse::RecDescent from CPAN, but it requires
> you to load the entire file into a string first. Too slow and too much
> memory for my purposes.
>
> (I know there's lex and yacc, but I don't know them very well and it's a
> fairly simple grammar that I could probably just code up from scratch
> just as well.)
>
>
> ____________________
> BYU Unix Users Group
> http://uug.byu.edu/
> ___________________________________________________________________
> List Info: http://uug.byu.edu/cgi-bin/mailman/listinfo/uug-list
--
David Smith <[EMAIL PROTECTED]>
____________________
BYU Unix Users Group
http://uug.byu.edu/
___________________________________________________________________
List Info: http://uug.byu.edu/cgi-bin/mailman/listinfo/uug-list
