need idiom - compare a number to a string

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

Replies are listed 'Best First'.
Re: need idiom - compare a number to a string by davidrw (Prior) on Mar 17, 2006 at 23:00 UTC
I think just doing `int($value) eq $value` should work (will still throw a warning if $value is undef). You could also regex it with something like `$value =~ /^[+-]?\d+$/` or Regexp::Common::number.	[reply] [d/l] [select]
Re: need idiom - compare a number to a string by brian_d_foy (Abbot) on Mar 18, 2006 at 01:03 UTC
Warnings are jsut warnings. Once you've seen it and decide that it's not a problem, you can turn it off for a bit. `{ # local $^W = 0; # old way no warnings; $value = ( int($value) == $value ) ? $value : lookupString( $value ); }` [download] However, if you're using constants in the code, strings are much better (if they are descriptive). Don't take a step backwards by making everything a magic number. :) -- brian d foy <brian@stonehenge.com> Subscribe to The Perl Review	[reply] [d/l]
Re: need idiom - compare a number to a string by swampyankee (Parson) on Mar 17, 2006 at 23:03 UTC
Since Perl will autostringify as needed, just check to see if `$value` looks like a number or not. I'd probably do something radically sub-optimal like `$value = lookupString($value) if($value !~ /^\d+$/);` [download] I'm sure one of the monks who has Perl skills above mine (i.e. almost everybody) has a better way, but I think my fragment will avoid too many errors (I'd probably demonstrate paranoia by checking to see if $value is defined before the match) added in update As chromatic pointed out, the regex I showed only checks for positive integers, with neither signs nor blank padding. Since the OP's posted code includes `int($value)`, I'm concluding values including a decimal point or in exponential notation aren't a concern. The regex should probably look more like this: `$value =~ /^\s[+-]?\s\d+\s*$/` [download] which should deal with signed and unsigned integers, but will reject cases where `$value` includes a radix point or is in exponential notation. emc " The most likely way for the world to be destroyed, most experts agree, is by accident. That's where we come in; we're computer professionals. We cause accidents. " — Nathaniel S. Borenstein	[reply] [d/l] [select]
Re^2: need idiom - compare a number to a string by chromatic (Archbishop) on Mar 17, 2006 at 23:19 UTC
Your regex only catches positive integers, which may be okay -- but it's certainly not all valid numbers. Consider negative integers, rationals, and numbers in scientific notation, for exammple.	[reply]
Re^3: need idiom - compare a number to a string by ikegami (Patriarch) on Mar 18, 2006 at 00:08 UTC
It don't think we have to catch those (well, maybe negatives). It sounds like the OP is talking error codes or something similar, which wouldn't be floating point numbers.	[reply]