Posted by Anno Siegel on 09/15/05 10:19

www.douglassdavis.com <doug@douglassdavis.com> wrote in comp.lang.perl.misc:
> I am using the preg_match function (in PHP) that uses perl regular
> expressions. Apparently I don't really understand regular expressions
> though. Could some one explain this?
>
> If this is the regular expression
>
> /^\s*(\d+\.\d+)|(\.\d+)|(\d+)\s*$/
>
> How does this:
>
> 40:26:46.302N 79:56:55.903W
>
> match? I thought when I added the ^ and $ that meant it had to match
> the whole thing? It seems to only be matching .302

Concatenation binds tighter than alternation. So the first alternative
is anchored to the left margin and the last one is anchored to the right
margin. The middle one isn't anchored and matched what it can.

Anno
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