Regex Number followed by symbol issue

[mathceleb]

Why is the 3rd term not -6_?

PHP Code:

$lefteq="-x+2+10x-9-6_";
$lct = preg_match_all('/(\-)?(\d+)(\-|\+|\=|\>|\<|\_)/', $lefteq, $match, PREG_PATTERN_ORDER);
for ($x=0;$x<$lct;$x++){
$curvalue=$match[0][$x];
echo "curvalue = " . $curvalue . "<br />";
$curvalue=substr($curvalue,0,strlen($curvalue)-1);
array_push($lconst,$curvalue);
} 


which produces

PHP Code:

curvalue = 2+
curvalue = -9-
curvalue = 6_ 


[MattF]

$lct = preg_match_all('/(\-)?(\d+?)(\-|\+|\=|\>|\<|\_)/', $lefteq, $match, PREG_PATTERN_ORDER);

or:

$lct = preg_match_all('/(\-)?(\d+)(\-|\+|\=|\>|\<|\_)/u', $lefteq, $match, PREG_PATTERN_ORDER);

or:

$lct = preg_match_all('/^(\-)?(\d+)(\-|\+|\=|\>|\<|\_)/', $lefteq, $match, PREG_PATTERN_ORDER);

should do as you expect.

[mathceleb]

2 of them did the same as what I had, and the one with the line starter ^ showed nothing.

[MattF]

What is it supposed to match? All or part of the string? If partial, which part? Btw, do a search on Google or such for 'PCRE cheat sheet'. It'll help with the specifics of regex.

[mathceleb]

It is supposed to match any number, positive or negative, followed by an operator sign or an underscore.

The only trouble I have in unit testing is that a negative number followed by a negative number comes up as negative positive. Everything else works like a charm.

I'll check the cheatsheet out.

[mathceleb]

Tried this instead, I removed the underscore from the end of $lefteq:
I'm looking for any number not followed by a letter. This gives the last negative number, but also gives the 1 in the number 10.

PHP Code:

$lct = preg_match_all('/(\-?)(\d+)(?![a-z])/', $lefteq, $match, PREG_PATTERN_ORDER); 


[mathceleb]

Fixed. I needed boundaries on the number. This solves my problem:

PHP Code:

$lct = preg_match_all('/(\-?)\b(\d+)\b(?![a-z])/', $lefteq, $match, PREG_PATTERN_ORDER); 


[MattF]

Originally Posted by mathceleb

I'm looking for any number not followed by a letter.

I'm a bit rusty, but try this:

preg_match_all('/(\d+)(?![a-z])/', $lefteq, $match, PREG_PATTERN_ORDER);

Try looking in $match[1] instead of $match[0] too.


Edit: You shouldn't need to use the boundary marker.