NAME

FP::Abstract::Compare - comparison protocol

SYNOPSIS

    package FPCompareExample::Foo {
        use FP::Struct ["num"];
        sub FP_Compare_compare {
            my ($a, $b) = @_;
            # let's make the default sort order reversed for the sake
            # of a more interesting example:
            $b->num cmp $a->num
        }
        _END_
    }

    use FP::PureArray; use FP::Ops 'the_method'; use FP::Equal qw(is_equal);
    is_equal( purearray(2,3,-7,4,2,8)
                 ->map(\&FPCompareExample::Foo::c::Foo)
                    ->sortCompare
                       ->map(the_method("num")),
              purearray(8, 4, 3, 2, 2, -7));

DESCRIPTION

Objects implementing this protocol can be ordered unambiguously.

The `$a->FP_Compare_compare($b)` returns -1 if $a is to be ordered before $b (is smaller), 0 if they are to be ordered into the same position, 1 if $a is to be ordered after $b.

This method is used for the default sort order by the `sort` method offered on sequences.

SEE ALSO

FP::Compare

NOTE

This is alpha software! Read the status section in the package README or on the website.