Re^7: Reliably parsing an integer

Besides, the "eq" is actually converting the integer back to a string, which will cost performance.

#!/usr/bin/env perl 
use strict;
use warnings;

use Benchmark 'timethis';

timethis (10_000_000, "valid_int ('18446744073709551614')");

sub valid_int {
    my $num = shift;
    return unless $num =~ /^\d+$/a;
    return int $num eq $num;
}

__END__

timethis 10000000:  8 wallclock secs ( 7.93 usr +  0.00 sys =  7.93 CP
+U) @ 1261034.05/s (n=10000000)
[download]

So, less than a microsecond on my aging system. Doubtless this can be improved upon (although about half the time taken appears to be the regex so there's a limit there too).

Comment on Re^7: Reliably parsing an integer Download Code

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Re^8: Reliably parsing an integer by rdiez (Acolyte) on Jun 30, 2020 at 10:34 UTC
This is the code I came up with, search for parse_unsigned_integer here: https://github.com/rdiez/Tools/blob/master/RDChecksum/rdchecksum.pl Can you see any bugs?	[reply]
Re^9: Reliably parsing an integer by syphilis (Archbishop) on Jun 30, 2020 at 13:08 UTC
Can you see any bugs? In perl, strings like "2e5" and "1E4" are valid integer strings. Are they being handled as you would like ? (I haven't investigated, and it depends upon how you want them to be treated.) If you want to accept them then you also have to keep in mind that if they represent values greater than ~0 or less than -(~0 >> 1) then they'll be assigned to NVs (floating point values) rather than IVs (integer value). I guess it's probably simplest if you reject them. Update, correcting an earlier incorrect update: After I wrote this post I discovered that if you assign a value like 2e5 as a bareword, you get an NV, not an IV - and I therefore thought I had made a mistake in asserting that such strings were "integer strings". However, although the barewords often assign as an NV, the above assertions seem to be correct in relation to numifying strings. It seems a bit random. We get an NV with: `C:\>perl -MDevel::Peek -le "$x = 1e6; Dump $x;" SV = NV(0x488470) at 0x488488 REFCNT = 1 FLAGS = (NOK,pNOK) NV = 1000000` [download] but an IV if we perform some arithmetic function: `C:\>perl -MDevel::Peek -le "$x = 1e6 * 1.0; Dump $x;" SV = IV(0x4ecb10) at 0x4ecb20 REFCNT = 1 FLAGS = (IOK,pIOK) IV = 1000000` [download] and, as regards what I've written above, if we numify the string we still get an IV: `C:\>perl -MDevel::Peek -le "$x = '1e6' * 1.0; Dump $x;" SV = IV(0x33d010) at 0x33d020 REFCNT = 1 FLAGS = (IOK,pIOK) IV = 1000000` [download] unless the value represented by the string is outside of the IV range: `C:\>perl -MDevel::Peek -le "$x = '1e70' * 1.0; Dump $x;" SV = NV(0x576440) at 0x576458 REFCNT = 1 FLAGS = (NOK,pNOK) NV = 1e+70` [download] Cheers, Rob	[reply] [d/l] [select]
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