regex for Err operator.

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi, Iam trying to write a source filter using Filter::Simple to use the Binary // (Err) operator in perl6. Iam having a tough time to construct the regex for this. I do have a semi working regex to substitute

$foo = $bar // $baz ;

s/(.*\s*)(.*)\b\s*\/\/\s*(.*)\b/$1defined($2) ? $2 : $3/gm;
[download]

But I wanted to know if there was a better way of constructing the regex Thanks Ragavendar

Comment on regex for Err operator. Download Code

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Re: regex for Err operator. by dave_the_m (Monsignor) on Aug 23, 2005 at 18:29 UTC
Are you aware that a patch is available for recent releases of perl 5.8.x to add this feature? Dave.	[reply]
Re^2: regex for Err operator. by Anonymous Monk on Aug 23, 2005 at 18:49 UTC
Hi, I thought it was going to be only released in 5.10 but will take a look at it. But for just the programming satisfaction I wanted to write a source filter. But my knowledge in regex are not upto the mark. At least for the learning aspect I want to get the regex for this. Thanks Raga	[reply]
Re: regex for Err operator. by davidrw (Prior) on Aug 23, 2005 at 18:23 UTC
the actual problem aside, my first thought is to use a different delimiter to make a little more legible (avoid having to escape the slashes): `s#(.\s)(.)\b\s//\s(.)\b#$1defined($2) ? $2 : $3#gm;` [download] Second thought is that at least some (if not most) of the `*` (0 or more) should be `+` (1 or more). Without them, the regex will match just the string "//". also, should "$1defined" be "$1 defined" ?	[reply] [d/l] [select]
Re^2: regex for Err operator. by Anonymous Monk on Aug 23, 2005 at 18:32 UTC
Hi, Thanks for your reply. The Err operator is a Binary operator in perl6 and it is //. A binary // operator is the defaulting operator. That is: $a // $b is short for: defined($a) ? $a : $b Because this operator is very useful Iam writing a source filter. Thanks, Raga	[reply]