Re^2: Incorrect Pattern Matching Behavior

Thanks for the quick reply. I actually don't want it to match this line. The line I'm looking for should look something like:

S 0.0 0.0 (OUTPUT)

How is this matching at all when the input doesn't have a first character of "S"? Shouldn't the ^S be enough to say that this line does not match?

Also, it uses $\s*INOUT|OUTPUT\s*$. How can this match when there are non whitespaces between the opening ( and the string OUTPUT?

My rules I guess would be

Starts with S
Two floats (could be negative or integer portion only)
Opening parentheses possibly followed by whitespace
Either INOUT or OUTPUT (case insensitive) possibly followed by whitespace
Closing parentheses

I may be very confused here, so your help is much appreciated.

Comment on Re^2: Incorrect Pattern Matching Behavior

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Re^3: Incorrect Pattern Matching Behavior by hv (Prior) on Mar 22, 2006 at 02:03 UTC
The problem is in the implementation of this clause: `Either INOUT or OUTPUT` [download] Your regular expression is getting parsed as: `/ # either this ^ S \s+ [-]* \d+ [\.\d+]* \s+ [-]* \d+ [\.\d+]* \s* $ \s* IOPUT \| # or this OUTPUT \s* $ /ix` [download] To achieve your aims, you need to tell perl where your list of alternates starts and ends, with capturing `(...)` or non-capturing `(?:...)` parens: `/ # all of this ^ S \s+ [-]* \d+ [\.\d+]* \s+ [-]* \d+ [\.\d+]* \s* $ \s* # and one of these two (?: IOPUT \| OUTPUT ) # and all of this \s* $ /ix` [download] I'd also recommend using the extended layout permitted by the `//x` flag for long expressions like this. Hope this helps, Hugo	[reply] [d/l] [select]
Re^3: Incorrect Pattern Matching Behavior by McDarren (Abbot) on Mar 22, 2006 at 01:59 UTC
Shouldn't the ^S be enough to say that this line does not match? Yes, I believe it should - and I'm afraid that part of it also has me stumped. Perhaps some other monk can explain why that is so. Update: ahh, of course - as others have pointed out below - it's because you haven't used parentheses to define the boundaries of your alternation :) Anyhow, getting back to your requirements, here is how I would do it: Update: oops, I just realised that I posted the wrong pattern. It can be simplified somewhat by grouping the part that matches the floats and using the `{2}` quantifier. I've updated it (output remains the same) `use strict; use warnings; while (<DATA>) { if (/^S\s+(?:\-?\d+(?:\.\d+)?\s+){2}$\s?(?:(INOUT\|OUTPUT))\s?$/) + { print "Matched:$_"; } else { print "Did NOT match:$_"; } } __DATA__ onn (bbcreccsnnl_output) !OUTPUT S 0.0 0.0 (OUTPUT) A 0.0 0.0 (OUTPUT) S 1 4 5 (OUTPUT) S 35 -27 ( INOUT ) S -26.95 32.73 (OUTPUT )` [download] The above outputs: `Did NOT match: onn (bbcreccsnnl_output) !OUTPUT Matched:S 0.0 0.0 (OUTPUT) Did NOT match:A 0.0 0.0 (OUTPUT) Did NOT match:S 1 4 5 (OUTPUT) Matched:S 35 -27 ( INOUT ) Matched:S -26.95 32.73 (OUTPUT )` [download] Which I believe meets your requirements, yes?	[reply] [d/l] [select]