# Copyright 2011, 2012, 2013, 2014 Kevin Ryde
# This file is part of Math-NumSeq.
#
# Math-NumSeq is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 3, or (at your option) any later
# version.
#
# Math-NumSeq is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with Math-NumSeq. If not, see <http://www.gnu.org/licenses/>.
package Math::NumSeq::Base::IteratePred;
use 5.004;
use strict;
use List::Util 'max';
use vars '$VERSION';
$VERSION = 69;
# uncomment this to run the ### lines
# use Smart::Comments;
use constant characteristic_increasing => 1;
use constant characteristic_integer => 1;
use constant characteristic_smaller => 0;
sub rewind {
my ($self) = @_;
### IteratePred rewind() ...
$self->{'i'} = $self->i_start;
my $value = $self->values_min;
if (! defined $value) { die "Oops, no values_min() for predicate start"; }
$self->{'value'} = $value;
### i: $self->{'i'}
### $value
}
sub next {
my ($self) = @_;
### IteratePred next() at value: $self->{'value'}
for (my $value = $self->{'value'}; ; $value++) {
if ($self->pred($value)) {
$self->{'value'} = $value+1;
return ($self->{'i'}++, $value);
}
}
}
# Would have to scan all values to find correct i.
# sub seek_to_value {
# my ($self, $value) = @_;
# $value = int($value);
# $self->{'value'} = max ($value, $self->values_min);
# $self->{'i'} = ...
# }
# Slow to scan through all values.
# sub ith {
# my ($self, $i) = @_;
# $i -= $self->i_start;
# my $value = $self->value_min - 1;
# while ($i >= 0) {
# $value++;
# if ($self->pred($value)) {
# $i--;
# }
# }
# return $value;
# }
1;
__END__
=for stopwords Ryde Math-NumSeq multi-inheritance
=head1 NAME
Math::NumSeq::Base::IteratePred -- iterate by searching with pred()
=for test_synopsis my @ISA
=head1 SYNOPSIS
package MyNumSeqSubclass;
use Math::NumSeq;
use Math::NumSeq::Base::IteratePred;
@ISA = ('Math::NumSeq::Base::IteratePred',
'Math::NumSeq');
sub ith {
my ($self, $i) = @_;
return something($i);
}
=head1 DESCRIPTION
This is a multi-inheritance mix-in providing the following methods
rewind() # return to $self->i_start() and $self->values_min()
next() # search using $self->pred()
characteristic_increasing() # always true
characteristic_integer() # always true
C<next()> iterates by searching for values satisfying
C<$self-E<gt>pred($value)>, starting at C<values_min()> and stepping by 1
each time.
This is a handy way to implement the iterating methods for a C<NumSeq> if
there's no easy way to step or have random access to values, only a test of
a condition.
The current implementation is designed for infinite sequences, it doesn't
check for a C<values_max()> limit.
The two "characteristic" methods mean that calls
$self->characteristic('increasing')
$self->characteristic('integer')
are both true. "Increasing" is since C<next()> always searches upwards.
"Integer" currently presumes that the starting C<values_min()> is an
integer.
=head1 SEE ALSO
L<Math::NumSeq>
=head1 HOME PAGE
L<http://user42.tuxfamily.org/math-numseq/index.html>
=head1 LICENSE
Copyright 2011, 2012, 2013, 2014 Kevin Ryde
Math-NumSeq is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
Math-NumSeq is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
You should have received a copy of the GNU General Public License along with
Math-NumSeq. If not, see <http://www.gnu.org/licenses/>.
=cut