#
# This file is part of Language::Befunge.
# Copyright (c) 2001-2009 Jerome Quelin, all rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the same terms as Perl itself.
#
#
package Language::Befunge::lib::MODU;
use strict;
use warnings;
use POSIX qw{ floor };
sub new { return bless {}, shift; }
# -- modulus
#
# $mod = M( $x, $y );
#
# signed-result modulo: x MOD y = x - FLOOR(x / y) * y
#
sub M {
my ($self, $lbi) = @_;
my $ip = $lbi->get_curip;
my $y = $ip->spop;
my $x = $ip->spop;
my $mod = $y == 0
? 0
: $x - floor($x/$y)*$y;
$ip->spush($mod);
}
#
# $mod = U( $x, $y );
#
# Sam Holden's unsigned-result modulo... No idea who this Sam Holden is
# or if he has a special algorithm for this, therefore always returning
# absolute value of standard modulo.
#
sub U {
my ($self, $lbi) = @_;
my $ip = $lbi->get_curip;
my $y = $ip->spop;
my $x = $ip->spop;
if ( $y == 0 ) {
$ip->spush(0);
return;
}
my $mod = $x % $y;
$ip->spush(abs($mod));
}
#
# $mod = R( $x, $y );
#
# C-language integer remainder: old C leaves negative modulo undefined
# but C99 defines it as the same sign as the dividend so that's what we're
# going with.
#
sub R {
my ($self, $lbi) = @_;
my $ip = $lbi->get_curip;
my $y = $ip->spop;
my $x = $ip->spop;
if ( $y == 0 ) {
$ip->spush(0);
return;
}
my $mod = $x % $y;
if ( ($x <= 0 && $mod <= 0) || ($x >= 0 && $mod >= 0)) {
$ip->spush( $mod );
} else {
$ip->spush( -$mod );
}
}
1;
__END__
=head1 NAME
Language::Befunge::IP::lib::MODU - Modulo Arithmetic extension
=head1 DESCRIPTION
The MODU fingerprint (0x4d4f4455) implements some of the finer, less-well-
agreed-upon points of modulo arithmetic. With positive arguments, these
instructions work exactly the same as C<%> does. However, when negative
values are involved, they all work differently.
=head1 FUNCTIONS
=head2 new
Create a new MODU instance.
=head2 Modulo implementations
=over 4
=item $mod = M( $x, $y )
Signed-result modulo: x MOD y = x - FLOOR(x / y) * y
=item $mod = U( $x, $y )
Sam Holden's unsigned-result modulo... No idea who this Sam Holden is
or if he has a special algorithm for this, therefore always returning
absolute value of standard modulo.
=item $mod = R( $x, $y )
C-language integer remainder: old C leaves negative modulo undefined
but C99 defines it as the same sign as the dividend so that's what we're
going with.
=back
=head1 SEE ALSO
L, L.
=head1 AUTHOR
Jerome Quelin, C<< >>
=head1 COPYRIGHT & LICENSE
Copyright (c) 2001-2009 Jerome Quelin, all rights reserved.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut