Is there a way I can substitute for ":" except when it is preceded by a letter C

kirk123 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Is there a way I can substitute for ":" except when it is preceded by a letter C by DamnDirtyApe (Curate) on Aug 16, 2002 at 23:18 UTC
Use a negative look-behind assertion. `$str =~ s/(?<!C):/"/g ;` [download] _______________ DamnDirtyApe Those who know that they are profound strive for clarity. Those who would like to seem profound to the crowd strive for obscurity. --Friedrich Nietzsche	[reply] [d/l]
Re: Is there a way I can substitute for ":" except when it is preceded by a letter C by tachyon (Chancellor) on Aug 16, 2002 at 23:20 UTC
A negative look behind asserion will do the trick, see perlman:perlre on lookahead and look behind assertions both positive and negative for more details. `$_ = 'c:--->j:a:p:h:,:'; s/(?<![cC]):/!/g; print;` [download] You could just use 'C' instead of the character class `[cC]` which makes this case insensitive. Of course you could also use /i at the end to do this but the character class was included in case you want to skip stuff like D:.... cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply] [d/l] [select]
Re: Is there a way I can substitute for ":" except when it is preceded by a letter C by BrowserUk (Patriarch) on Aug 16, 2002 at 23:57 UTC
Or if the phrase "negative lookbehind assertion" fills you with dread ... `my $string = 'Engine4.2.0.5:prefix=PDE:path=C:\h\COE\COMP\PDE:status=installed:vers +ionNumber=4.2.0.5:type=SOFTWARE-COE:'; $string =~ s/([^C]):/$1'/g;` [download] ...will do it too. Update: ...almost:( See Tachon's post below for how to do it properly {sigh}. It reads; capture any single non-"C" char followed by a ":" and replace both by the captured char ($1) and the "'". What's this about a "crooked mitre"? I'm good at woodwork!	[reply] [d/l]
Re: Re: Is there a way I can substitute for ":" except when it is preceded by a letter C by tachyon (Chancellor) on Aug 17, 2002 at 01:19 UTC
But what if the string is ':foo'? `s/([^C:]*):/$1'/g;` [download] cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply] [d/l]
Re: Re: Re: Is there a way I can substitute for ":" except when it is preceded by a letter C by MrNobo1024 (Hermit) on Aug 17, 2002 at 02:35 UTC
That's not quite right, the * makes it match even if there's 0 C's, turning all colons into apostrophes, not just the intended ones `s/(^\|[^C]):/$1'/g` [download] fixes that, but won't work if there is multiple colons in a row. A negative lookbehind is probably the only way to do this properly. --MrNobo1024 `s]]HrLfbfe\|EbBibmv]e\|s}w}ciZx^RYhL}e^print`	[reply] [d/l]