# Copyright 2011, 2012, 2013 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::DigitSumSquares;
use 5.004;
use strict;
use vars '$VERSION', '@ISA';
$VERSION = 7;
use Math::NumSeq;
use Math::NumSeq::Base::IterateIth;
@ISA = ('Math::NumSeq::Base::IterateIth',
'Math::NumSeq');
# uncomment this to run the ### lines
#use Smart::Comments;
use constant name => Math::NumSeq::__('Digit Sum of Squares');
use constant description => Math::NumSeq::__('Sum of the squares of the digits in the given radix. (For binary this is how many 1-bits.)');
use constant values_min => 0;
use constant characteristic_increasing => 0;
use constant characteristic_smaller => 1;
use Math::NumSeq::Base::Digits
'parameter_info_array'; # radix parameter
#------------------------------------------------------------------------------
my @oeis_anum;
$oeis_anum[2] = 'A000120'; # 2 binary, number of 1s, cf DigitCount
$oeis_anum[10] = 'A003132';
# OEIS-Catalogue: A003132
sub oeis_anum {
my ($self) = @_;
return $oeis_anum[$self->{'radix'}];
}
#------------------------------------------------------------------------------
# ENHANCE-ME:
# next() is add 2*d+1 until wrap around then subtract
#
# sub next {
# my ($self) = @_;
# my $radix = $self->{'radix'};
# my $sum = $self->{'sum'} + 1;
# if (++$self->{'digits'}->[0] >= $radix) {
# $self->{'digits'}->[0] = 0;
# my $i = 1;
# for (;;) {
# $sum++;
# if (++$self->{'digits'}->[$i] < $radix) {
# last;
# }
# }
# }
# return ($self->{'i'}++, ($self->{'sum'} = ($sum % $radix)));
# }
sub ith {
my ($self, $i) = @_;
my $radix = $self->{'radix'};
my $sum = 0;
while ($i) {
$sum += ($i % $radix) ** 2;
$i = int($i/$radix)
}
return $sum;
}
sub pred {
my ($self, $value) = @_;
return ($value == int($value)
&& $value >= 0);
}
1;
__END__
=for stopwords Ryde Math-NumSeq
=head1 NAME
Math::NumSeq::DigitSumSquares -- sum of digits
=head1 SYNOPSIS
use Math::NumSeq::DigitSumSquares;
my $seq = Math::NumSeq::DigitSumSquares->new (radix => 10);
my ($i, $value) = $seq->next;
=head1 DESCRIPTION
The sum of squares of digits in each i, so 0, 1, 4, 9, 16, ..., 81, 1, 2, 5,
10, .., etc. For example at i=123 the value is 1*1+2*2+3*3=14.
=head1 FUNCTIONS
See L<Math::NumSeq/FUNCTIONS> for behaviour common to all sequence classes.
=over 4
=item C<$seq = Math::NumSeq::DigitSumSquares-E<gt>new ()>
=item C<$seq = Math::NumSeq::DigitSumSquares-E<gt>new (radix =E<gt> $r)>
Create and return a new sequence object. The default radix is 10,
ie. decimal, or a C<radix> parameter can be given.
=back
=head2 Random Access
=over
=item C<$value = $seq-E<gt>ith($i)>
Return the sum of the digits of C<$i>.
=item C<$bool = $seq-E<gt>pred($value)>
Return true if C<$value> occurs as the sum of squares of digits, which means
simply C<$value E<gt>= 0>. Any integer C<$value> can occur from all-ones
11..11.
=back
=head1 SEE ALSO
L<Math::NumSeq>,
L<Math::NumSeq::DigitSum>
=head1 HOME PAGE
http://user42.tuxfamily.org/math-numseq/index.html
=head1 LICENSE
Copyright 2011, 2012, 2013 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