NAME
Math::NoCarry  Perl extension for no carry arithmetic
SYNOPSIS
use Math::NoCarry qw(:all);
my $sum = add( 123, 456 );
my $difference = subtract( 123, 456 );
my $product = multiply( 123, 456 );
DESCRIPTION
No carry arithmetic doesn't allow you to carry digits to the next column. For example, if you add 8 and 4, you normally expect the answer to be 12, but that 1 digit is a carry. In no carry arithmetic you can't do that, so the sum of 8 and 4 is just 2. In effect, this is addition modulo 10 in each column. I discard all of the carry digits in this example:
1234
+ 5678

6802
For multiplication, the result of pairwise multiplication of digits is the modulo 10 value of their normal, everyday multiplication.
123
x 456

8 6 x 3
2 6 x 2
6 6 x 1
5 5 x 3
0 5 x 2
5 5 x 1
2 4 x 3
8 4 x 2
+ 4 4 x 1

43878
Since multiplication and subtraction are actually types of additions, you can multiply and subtract like this as well.
No carry arithmetic is both associative and commutative.
Functions
As of version 1.11, all of these functions are exportable on demand, or with the tag :all
to get them all at once.
 multiply( A, B )

Returns the no carry product of A and B.
Return A if it is the only argument ( A x 1 );
 add( A, B )

Returns the no carry sum of the positive numbers A and B.
Returns A if it is the only argument ( A + 0 )
Returns false if either number is negative.
 subtract( A, B )

Returns the no carry difference of the postive numbers A and B.
Returns A if it is the only argument ( A  0 )
Returns false if either number is negative.
BUGS
* none reported yet :)
TO DO
* this could be a full object package with overloaded +, *, and  operators
* it would be nice if i could give the functions more than two arguments.
* addition and subtraction don't do negative numbers.
SOURCE AVAILABILITY
This source is part of a SourceForge project which always has the latest sources in SVN, as well as all of the previous releases.
http://sourceforge.net/projects/briandfoy/
If, for some reason, I disappear from the world, one of the other members of the project can shepherd this module appropriately.
AUTHOR
brian d foy, <bdfoy@cpan.org>
COPYRIGHT AND LICENSE
Copyright (c) 20022007 brian d foy. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.