Re: Regex woes...

You regexp is correct except for the (-) part. The (-) requires there to be a - there and caputures it into $2. In this case the parens aren't really necessary. However, you probably want a ? after the -. The ? after something means that it may occur zero or one time.

That said, you might want to replace the (-) not with -? but with [-+]?. [-+] creates a character class matching - or +, so it would allow numbers like +157.0.

I think you probably want a $ or \z at the end of your regex to say that the end must be either the end of the string or a newline before it (for $), or the end of the string, no exceptions, (for \z.)

perlre is your friend, as always.

update: As adamsj pointed out you also used - instead of , with \d{1-3}. I read too fast to notice.

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Re: Re: Regex woes... by adamsj (Hermit) on Jul 09, 2001 at 03:55 UTC
And that raises an interesting point, which probably has a trivial answer which I don't know. Why doesn't a construct like \d{1-3} make -w scream? Even more oddly, if it's reversed to say \d{3-1}, it neither makes -w scream nor does it DWIM and match, say, -12.3, like it would if it were \d{2}. adamsj They laughed at Joan of Arc, but she went right ahead and built it. --Gracie Allen	[reply]
Re: Re: Re: Regex woes... by wog (Curate) on Jul 09, 2001 at 04:06 UTC
`-Mre=debug` reveals the answer: ... Compiling REx `\d{3-1}' ... 1: DIGIT(2) 2: EXACT <{3-1}>(5) 5: END(0) ... [download] Apparently this means the regex got compiled to match a digit, and then the literal text `{3-1}`. It would be nice if perl recognized that there might have been confusion with the `{M,N}` syntax, and thus would throw a warning, though issues of backwards compatiblity would need to be considered in doing this.	[reply] [d/l] [select]
Re: Re: Re: Regex woes... by japhy (Canon) on Jul 09, 2001 at 07:17 UTC
If you look at `regcomp.c`, you'll see that when the regx parser finds an open brace, it looks for digits, and optionally followed by a comma and another optional string of digits. Anything else falls through as plaintext. (See the `S_regpiece()` function.) `japhy` -- Perl and Regex Hacker	[reply]