Re: Howto strip 42 from comma separated list using s///

Is this maybe the regex that you're looking for? There may be more elegant ways, but this seems alot easier to decipher.

s/(,42\b|\b42,|^42$)//g;
[download]

Update: Added the case for a single element of just "42" per Not_a_Number's and Perl Mouse's suggestions. Good catch; that's what a quick solution gets me, I didn't test all cases. I should note too, the position of 42 at the end of the list is important, so the regex engine doesn't try and grab that without looking for commas first.
Update: Perl Mouse makes a good point here: 505335 on boundary checking too, so I made another mod to the regex to take that into account as well.
Update: Ok, this is it; no more updates. One catch w/ boundary checking is in the odd case of "41,I like 42 things, 43", which would replace the "42", but shouldn't. I think in the context of this question this is really isn't an issue and \b works fine. To combat that though, I just hit what really was being addressed, "^42$", where its the only element.
Update: lol. I give up; one more. Perl Mouse pointed out partial number matches, so the boundary checking is back in a modified form. He has this below too. I only mod it here so in case someone takes a quick glance, they can get my best version (with the help of mightier monks than I) instead of my regex version from like 4 iterations ago.

-jbWare

Comment on Re: Howto strip 42 from comma separated list using s/// Download Code

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Re^2: Howto strip 42 from comma separated list using s/// by Not_a_Number (Prior) on Nov 03, 2005 at 13:34 UTC
`s/(,42\|42,)//g;` The problem with this is that a list, by definition, might contain only one element. What if that element is 42?	[reply] [d/l]
Re^2: Howto strip 42 from comma separated list using s/// by Perl Mouse (Chaplain) on Nov 03, 2005 at 14:08 UTC
`s/(,42\|42,\|\b42\b)//g;` Tricky, isn't? Unfortunally, you still haven't cover all cases correctly: `$ perl -wle '$_ = "142,143"; s/(,42\|42,\|\b42\b)//g; print' 1143` [download] You need to anchor all cases: `s/,42\b\|\b42,\|^42$//; # Or s/\b(?:,42\|42,\|42)\b//; # Or s/\b42,\|,?42\b//;` [download] `Perl --((8:>*`	[reply] [d/l] [select]
Re^3: Howto strip 42 from comma separated list using s/// by jbware (Chaplain) on Nov 03, 2005 at 14:21 UTC
Yeah, and painful. Although it can be done it regex, it just goes to show why I would much rather iterate through a list and process each element individually instead of handling all the element special cases in a regex. From a processing efficiency standpoint I'm not sure which is better, but I think regarding a programmer's efficiency, and future understanding, I'd lean toward looping through a list and handling each element on its own as a better decision. It just seems cleaner to me (as fun as regex exercises are); but maybe that's just me. -jbWare	[reply]
Re^2: Howto strip 42 from comma separated list using s/// by Perl Mouse (Chaplain) on Nov 03, 2005 at 13:37 UTC
That wouldn't work on a list containing just '42'. It will the string unmodified instead of ending up with the empty string. `Perl --((8:>*`	[reply]


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