in reply to How to identify a number datatype in a string?

USe an eval, it's correct (by definition) and avoids possible errors

my @numbers = (       '1',     '2',       '10',
                    '1.2',   '1e2',   '1.02e2',
                '1.02e-2',   'e-2',       'er',
                     'et',   '0er'              );

foreach my $number (@numbers) {
    my $test = $number;
    eval { $test +=0; };
    if ( $@ ) {
        print "$number isn't a number \n";
    }
}

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{QA Editors note: This solution doesn't work as described. See Re: Answer: How to identify a number datatype in a string? for more explanation.}

Edited by davido: Repaired <code> tags, reformatted code. Added editorial note to clarify why this example is broken.

--

Anthony Staines

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Re: Answer: How to identify a number datatype in a string?
by hossman (Prior) on May 30, 2003 at 06:31 UTC
    Uh, this doesn't seem to work at all... 
    laptop:~> perl -T
my @numbers = ('1','2','10','1.2','1e2','1.02e2',
               '1.02e-2','e-2','er','et','0er',
               'total and complete non number stuff');
foreach my $number (@numbers) {
   my $test = $number;
   eval { $test +=0; }; 
   if ( $@ ) { print "$number isn't a number \n"; }
}
laptop:~>

    [download]
    Here are my particulars...
    Read more... (4 kB)
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      Add the following after if(@){}, and you will see...

        else { print "number: ", $test , "\n"; }

      [download]

      ...Apparently, $test is assigned zero (perl 5.8.0) when $number is not a number. Ergo, no errors in eval, no print.

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        Acctually, $test is assigned $number regardless of what $number is ... if you do any mathematicly operations on a scalar which is "not a number" then that scalar is evaluated as "0" (and a warning is generated).

        Which was basicly my point ... the whole premese of this test is flawed. (uless you set up a signal handler for warnings, which causes a "die" to be thrown)

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