pattern matching an array, not their elements per se

Question

Hi

I'm looking for a way of pattern matching the "geometry" of an array, the order in which the elements appear, not the contents of each element directly.

Let me outline what I mean by some examples. Given the target array:

array('T_STRING','T_VARIABLE','ASSIGN','T_STRING','LPAREN','T_VARIABLE','COMMA','T_VARIABLE','RPAREN');
//as a matter of fact, these would be the tokens for the PHP code "foo $var = Foo($arg1,$arg2)'

Then the following "pattern" would match, returning the 0-based indexes of the matches, as well as the indexes of the groupings, just like preg_match_all() would do for strings:

array('T_STRING', '?', '(', 'T_VARIABLE', 'ASSIGN' ')', '?',
    'T_STRING', 'LPAREN', '(', 'T_VARIABLE', 'COMMA', '?', ')', '?', 'RPAREN');

This is only a simplified PoC, the way I intend to use it is much more complicated, and I don't want to use the full parser generator from PEAR (the lemon port to PHP), which would be overkill.

Are you aware of a function (possibly not an internal PHP function) or project which does just that?

Thank you.

Answer 1

When ever I hear "pattern matching" I think "regex".

Push that array to a string and match against the pattern you're looking for using regex. You may be able to a symbol replacement to make the regex small and manageable:

Your array above could be reduced to a string like this:

$arrayPattern = 'SVASL_PVCVR_P'

Now you can use RegEx to match against it.

if (preg_match('/VA/', $arrayPattern)) 
  print "You've got a Variable followed by an Assign!";

Just a thought....

Answer 2

If you are you looking for Code Analysis, then these slides of Sebastian Bergmann might be of use to you. Starting with slide 17 is examples for analysis by tokens.