Perl - Is this a bug with looks_like_number, or am I being a stupid person? -

this code:

#!/usr/bin/perl -w  use strict; use scalar::util qw(looks_like_number);  sub what_the_fudge {     $string = "foo 123 bar";     if ($string =~ /foo (.+) bar/) {         if (looks_like_number($1)) {             print "$1 looks number\n";         } else {             print "$1 doesnt number\n";         }     } }  &what_the_fudge; &what_the_fudge; &what_the_fudge; 

displays this:

123 doesnt number 123 looks number 123 looks number 

why fail recognize number first time? =( baffles me.

some information environment:

os: osx 10.6.8

perl -e 'use scalar::util; print "$scalar::util::version\n"' --> 1.19

perl -v --> perl, v5.10.0 built darwin-thread-multi-2level (with 2 registered patches, see perl -v more detail)

it's bug fixed in scalar::util 1.20. ("handle overloaded , tied values" in changes file.)

the xs version of looks_like_number failed handle magical arguments properly. magic allows code called when operations performed on variable (such fetching value).

solutions:

• upgrade scalar::util 1.20 or higher.
• delete compiled component of scalar::util force use of pure perl implementation doesn't suffer problem.
• use looks_like_number("$1") creates non-magical copy of $1 right value.

---

1.19:

int looks_like_number(sv)         sv *sv prototype: $ code: #if (perl_version < 8) || (perl_version == 8 && perl_subversion <5)   if (svpok(sv) || svpokp(sv)) {     retval = looks_like_number(sv);   }   else {     retval = svflags(sv) & (svf_nok|svp_nok|svf_iok|svp_iok);   } #else   retval = looks_like_number(sv); #endif output:  retval 

1.21:

int looks_like_number(sv)     sv *sv prototype: $ code:   sv *tempsv;   if (svamagic(sv) && (tempsv = amg_callun(sv, numer))) {     sv = tempsv;   }   else if (svmagical(sv)) {       svgetmagic(sv);   } #if (perl_version < 8) || (perl_version == 8 && perl_subversion <5)   if (svpok(sv) || svpokp(sv)) {     retval = looks_like_number(sv);   }   else {     retval = svflags(sv) & (svf_nok|svp_nok|svf_iok|svp_iok);   } #else   retval = looks_like_number(sv); #endif output:   retval 

---

try this:

what_the_fudge("foo 123 bar"); what_the_fudge("foo baz bar"); what_the_fudge("foo 123 bar");  sub what_the_fudge {     $string = shift; 

i haven't tried it, should get

version of scalar::util: 1.19 doesnt number looks number doesnt number