Re: Re: numeric comparison

Perl 5.8.1's stock Scalar::Util has looks_like_number(). Here's a little workout to show what it can and can't do,

use Scalar::Util 'looks_like_number';
my @candidates = qw/ 1 1.1 1,1 0E0 0e0 0377 100_000 0xdeadbeef/;

print $_,
      looks_like_number($_)? ' is' : ' is not',
      ' a number.',
      $/
    for @candidates;

__END__
1 is a number.
1.1 is a number.
1,1 is not a number.
0E0 is a number.
0e0 is a number.
0377 is a number.
100_000 is not a number.
0xdeadbeef not is a number.
[download]

After Compline,
Zaxo

Comment on Re: Re: numeric comparison Download Code

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Re: Re: Re: numeric comparison by BrowserUk (Patriarch) on Jul 15, 2003 at 15:06 UTC
I was a bit surprised by 100_000 not being recognised as a number but then I tried this `print 3 + '0xdeadbeef'; Argument "0xdeadbeef" isn't numeric in addition (+) at ... 3 print 3 + 0xdeadbeef; 3735928562 print 3+ '100_000'; Argument "100_000" isn't numeric in addition (+) at ... 103 print 3+ 100_000; 100003` [download] Which I guess means that the code used to extract a number from a string at runtime is a different routine to that used for parsing numeric constants at compile time. Which is slightly disappointing, but is probably done that way for very good reasons. I just wish that the version of Scalar-List-Utils on the AS 5.8 list included the compiled XS code. That is that possible isn't it? Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller	[reply] [d/l]

Replies are listed 'Best First'.

Re: Re: Re: numeric comparison
by BrowserUk (Patriarch) on Jul 15, 2003 at 15:06 UTC

I was a bit surprised by 100_000 not being recognised as a number but then I tried this

print 3 + '0xdeadbeef';
Argument "0xdeadbeef" isn't numeric in addition (+) at ...
3

print 3 + 0xdeadbeef;
3735928562

print 3+ '100_000';
Argument "100_000" isn't numeric in addition (+) at ...
103

print 3+ 100_000;
100003
[download]

Which I guess means that the code used to extract a number from a string at runtime is a different routine to that used for parsing numeric constants at compile time. Which is slightly disappointing, but is probably done that way for very good reasons.

I just wish that the version of Scalar-List-Utils on the AS 5.8 list included the compiled XS code. That is that possible isn't it?

Examine what is said, not who speaks.

"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller

[reply]
[d/l]