Increment/Decrement Operator with Strings

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

Replies are listed 'Best First'.
Re: Increment/Decrement Operator with Strings by wfsp (Abbot) on Sep 27, 2005 at 05:56 UTC
In perlop: The auto-decrement operator is not magical.	[reply]
Re: Increment/Decrement Operator with Strings by jbrugger (Parson) on Sep 27, 2005 at 08:07 UTC
I'm not fond of this kind of magic... `# this works #!/usr/bin/perl -w use strict; my $a = "a"; print ++$a ."\n"; print ++$a ."\n"; print ++$a ."\n"; # this also works #!/usr/bin/perl -w use strict; my $a = "a8"; print ++$a ."\n"; print ++$a ."\n"; print ++$a ."\n"; # but this is unpredictable #!/usr/bin/perl -w use strict; my $a = "a8y"; print ++$a ."\n"; print ++$a ."\n"; print ++$a ."\n";` [download] update Or better as posted by sh1tn: see the difference `perl -e '$char = "a"; print $char++, $/ for 1..20' perl -e '$char = "a0"; print $char++, $/ for 1..20' perl -e '$char = "a0a"; print $char++, $/ for 1..20'` [download] "We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise." - Larry Wall.	[reply] [d/l] [select]
Re: Increment/Decrement Operator with Strings by reasonablekeith (Deacon) on Sep 27, 2005 at 09:51 UTC
because, according to to Programming Perl... The autodecrement operator, however, is not magical. I guess you'll have to roll your own. Sorry. UPDATE: wfsp, I skimmed past your answer thinking you'd just posted a link to the docs, and didn't even read the last line, thinking it was a signature. --- my name's not Keith, and I'm not reasonable.	[reply]
Re: Increment/Decrement Operator with Strings by sh1tn (Priest) on Sep 27, 2005 at 07:57 UTC
The operator works just fine on chars: `# perl -e '$char = "a"; print $char++, $/ for 1..26'` [download] update: from perlop: "... The auto-increment operator has a little extra builtin magic to it. If you increment a variable that is numeric, or that has ever been used in a numeric context, you get a normal increment. If, however, the variable has been used in only string contexts since it was set, and has a value that is not the empty string and matches the pattern `"^[a-zA-Z][0-9]\z/"`, the increment is done as a string, preserving each character within its range ..." Nowhere is said the same about the auto-decrement operator, so why should someone expect similar behaviour?	[reply] [d/l] [select]
Re^2: Increment/Decrement Operator with Strings by holli (Abbot) on Sep 27, 2005 at 08:37 UTC
Of course. But that is not the question. The OP asks about the decrement operator, not the increment. holli, /regexed monk/	[reply] [d/l]
Re: Increment/Decrement Operator with Strings by ambrus (Abbot) on Sep 28, 2005 at 22:07 UTC
You could try Math::String	[reply]
Re: Increment/Decrement Operator with Strings by QM (Parson) on Sep 27, 2005 at 21:27 UTC
I recall that someone had some nifty hack or obfu to simulate this, but I can't find it right now. -QM -- Quantum Mechanics: The dreams stuff is made of	[reply]