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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);
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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