POSIX-Style character classes

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

I was practicing random one-liners on this rainy christmas day and I came across one that I can't seem to get right.

perl -e 'if('42'=~ /[:^digit:]/) {print "42 is a digit\n"}; else {prin
+t "42 is not a digit\n"}';
[download]

And the output is

>
>
>
[download]

and no shell prompt. I am sure its something simple I am just not seeing.
Thanks

"Es gibt mehr zu Leben als Bücher, kennen Sie. Aber nicht viel mehr " -(Der Smiths)

Comment on POSIX-Style character classes Select or Download Code

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Re: POSIX-Style character classes by borisz (Canon) on Dec 25, 2005 at 19:33 UTC
Perhaps you want: `perl -e 'if("42"=~ /^[[:digit:]]+$/) {print "42 is a digit\n"} else {p +rint "42 is not a digit\n"};'` [download] the inner [] is part of the charclass name. And do not mix ' and " for oneliners. Just start with ' and use " or q or qq in your oneliner on UNIX. Boris	[reply] [d/l]
Re: POSIX-Style character classes by ww (Archbishop) on Dec 25, 2005 at 21:42 UTC
I would argue that (quoting for windows users; language pedantry re digits for any who stumble upon this): `C:\>perl -e "if('42'=~ /^[[:digit:]]$/) {print qq(42 is a digit\n)} else {print qq(42 is not a digit\n)};"` which prints `42 is not a digit` is actually correct, given that while "4" and "2" are digits, "42" is NOT. However, if your intent was to test that the "42" is comprised exclusively of digits, then, `C:\>perl -e "if('42'=~ /^[[:digit:]]+$/) {print qq(42 is exclusively d +igits\n)} else {print qq(42 is not a digit\n)};"` [download] accurately prints: "42 is exclusively digits" because the second 1-liner above tests for one_or_more digits.	[reply] [d/l] [select]
Re: POSIX-Style character classes by HuckinFappy (Pilgrim) on Dec 26, 2005 at 03:33 UTC
I see two problems: The mixing of ' and ". Your single quotes around the '42' are the first thing breaking you The semicolon afte the if { } and before the else `fappy@flux[62] tmp > perl -e 'if( q{42} =~ /[:^digit:]/) {print "42 is + a digit\n"} else {print "42 is not a digit\n"}'; 42 is not a digit` [download] Now the questions remainns, what did you really want to test?	[reply] [d/l]
Re: POSIX-Style character classes by TedPride (Priest) on Dec 26, 2005 at 02:56 UTC
Somewhat unrelated, it's neater to say: `print "42" =~ /^[[:digit:]]+$/ ? "42 is a digit" : "42 is not a digit" +;` [download]	[reply] [d/l]


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