there are reasons other than performance for wanting fix-width integer semantics

Definitely correct ... though I must confess that the reasons you've implicitly put forward in your demos were not exactly what I was thinking of when I acknowledged this (or tried to) in my earlier post.

For a Math::GMPz rendition of your demo I would put forward the following: 
#! perl -slw
use strict;
use Math::GMPz qw(:mpz);

my $ZERO = Math::GMPz->new( 0 );
my $ONE  = Math::GMPz->new( 1 );
#my $ALLONES = ~ $ZERO;
my $ALLONES = (Math::GMPz->new(1) << 128) - 1;
my $MASK1 = $ALLONES / 3;
my $MASK2 = $ALLONES / 15 * 3;
my $MASK3 = $ALLONES / 255;
my $MASK4 = $MASK3 * 15;

my $bits = Math::GMPz->new( 0 );

## set every 3rd bit
$bits |= $ONE << $_ for map $_*3+1, 0 .. 42;
print $bits;
## count the bits (43)
#print bcount( $bits );
print Rmpz_popcount($bits);

## now invert them and count again. (85)
#print bcount( ~$bits );
print Rmpz_popcount($ALLONES ^ $bits);

[download]
I hope it doesn't miss the point ... I think the only changes are that:
1) It changes the way that $ALLONES is created;
2) It removes the need for sub bcount()

Update: And, there's also now a qw(:mpz) in the third line.

Cheers,
Rob

In reply to Re^14: Module for 128-bit integer math? (updated) by syphilis
in thread Module for 128-bit integer math? by BrowserUk

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