use strict;
use warnings;
package Number::Tolerant::Union;
# ABSTRACT: unions of tolerance ranges
$Number::Tolerant::Union::VERSION = '1.708';
#pod =head1 SYNOPSIS
#pod
#pod  use Number::Tolerant;
#pod
#pod  my $range1 = tolerance(10 => to => 12);
#pod  my $range2 = tolerance(14 => to => 16);
#pod
#pod  my $union = $range1 | $range2;
#pod
#pod  if ($11 == $union) { ... } # this will happen
#pod  if ($12 == $union) { ... } # so will this
#pod
#pod  if ($13 == $union) { ... } # nothing will happen here
#pod
#pod  if ($14 == $union) { ... } # this will happen
#pod  if ($15 == $union) { ... } # so will this
#pod
#pod =head1 DESCRIPTION
#pod
#pod Number::Tolerant::Union is used by L<Number::Tolerant> to represent the union
#pod of multiple tolerances.  A subset of the same operators that function on a
#pod tolerance will function on a union of tolerances, as listed below.
#pod
#pod =head1 METHODS
#pod
#pod =head2 new
#pod
#pod   my $union = Number::Tolerant::Union->new(@list_of_tolerances);
#pod
#pod There is a C<new> method on the Number::Tolerant::Union class, but unions are
#pod meant to be created with the C<|> operator on a Number::Tolerant tolerance.
#pod
#pod The arguments to C<new> are a list of numbers or tolerances to be unioned.
#pod
#pod Intersecting ranges are not converted into a single range, but this may change
#pod in the future.  (For example, the union of "5 to 10" and "7 to 12" is not "5 to
#pod 12.")
#pod
#pod =cut

sub new {
  my $class = shift;
  bless { options => [ @_ ] } => $class;
}

#pod =head2 options
#pod
#pod This method will return a list of all the acceptable options for the union.
#pod
#pod =cut

sub options {
  my $self = shift;
  return @{$self->{options}};
}

#pod =head2 Overloading
#pod
#pod Tolerance unions overload a few operations, mostly comparisons.
#pod
#pod =over
#pod
#pod =item numification
#pod
#pod Unions numify to undef.  If there's a better idea, I'd love to hear it.
#pod
#pod =item stringification
#pod
#pod A tolerance stringifies to a short description of itself.  This is a set of the
#pod union's options, parentheses-enclosed and joined by the word "or"
#pod
#pod =item equality
#pod
#pod A number is equal to a union if it is equal to any of its options.
#pod
#pod =item comparison
#pod
#pod A number is greater than a union if it is greater than all its options.
#pod
#pod A number is less than a union if it is less than all its options.
#pod
#pod =item union intersection
#pod
#pod An intersection (C<&>) with a union is commutted across all options.  In other
#pod words:
#pod
#pod  (a | b | c) & d  ==yields==> ((a & d) | (b & d) | (c & d))
#pod
#pod Options that have no intersection with the new element are dropped.  The
#pod intersection of a constant number and a union yields that number, if the number
#pod was in the union's ranges and otherwise yields nothing.
#pod
#pod =back
#pod
#pod =cut

use overload
  '0+' => sub { undef },
  '""' => sub { join(' or ', map { "($_)" } $_[0]->options) },
  '==' => sub { for ($_[0]->options) { return 1 if $_ == $_[1] } return 0 },
  '!=' => sub { for ($_[0]->options) { return 0 if $_ == $_[1] } return 1 },
  '>'  =>
    sub {
      if ($_[2]) { for ($_[0]->options) { return 0 unless $_[1] > $_ } return 1 }
      else       { for ($_[0]->options) { return 0 unless $_[1] < $_ } return 1 }
    },
  '<'  =>
    sub {
      if ($_[2]) { for ($_[0]->options) { return 0 unless $_[1] < $_ } return 1 }
      else       { for ($_[0]->options) { return 0 unless $_[1] > $_ } return 1 }
    },
  '<=>' =>
    sub {
      if ($_[2]) { $_[0] < $_[1] ? 1 : $_[0] > $_[1] ? -1 : 0 }
      else       { $_[0] > $_[1] ? 1 : $_[0] < $_[1] ? -1 : 0 }
    },
  '|' => sub { __PACKAGE__->new($_[0]->options,$_[1]); },
  '&' => sub {
    eval { $_[1]->isa('Number::Tolerant') }
      ? __PACKAGE__->new(map { $_ & $_[1] } $_[0]->options )
      : $_[1] == $_[0]
        ? $_[1]
        : ();
    },
  fallback => 1;

#pod =head1 TODO
#pod
#pod Who knows.  Collapsing overlapping options, probably.
#pod
#pod =cut

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Number::Tolerant::Union - unions of tolerance ranges

=head1 VERSION

version 1.708

=head1 SYNOPSIS

 use Number::Tolerant;

 my $range1 = tolerance(10 => to => 12);
 my $range2 = tolerance(14 => to => 16);

 my $union = $range1 | $range2;

 if ($11 == $union) { ... } # this will happen
 if ($12 == $union) { ... } # so will this

 if ($13 == $union) { ... } # nothing will happen here

 if ($14 == $union) { ... } # this will happen
 if ($15 == $union) { ... } # so will this

=head1 DESCRIPTION

Number::Tolerant::Union is used by L<Number::Tolerant> to represent the union
of multiple tolerances.  A subset of the same operators that function on a
tolerance will function on a union of tolerances, as listed below.

=head1 METHODS

=head2 new

  my $union = Number::Tolerant::Union->new(@list_of_tolerances);

There is a C<new> method on the Number::Tolerant::Union class, but unions are
meant to be created with the C<|> operator on a Number::Tolerant tolerance.

The arguments to C<new> are a list of numbers or tolerances to be unioned.

Intersecting ranges are not converted into a single range, but this may change
in the future.  (For example, the union of "5 to 10" and "7 to 12" is not "5 to
12.")

=head2 options

This method will return a list of all the acceptable options for the union.

=head2 Overloading

Tolerance unions overload a few operations, mostly comparisons.

=over

=item numification

Unions numify to undef.  If there's a better idea, I'd love to hear it.

=item stringification

A tolerance stringifies to a short description of itself.  This is a set of the
union's options, parentheses-enclosed and joined by the word "or"

=item equality

A number is equal to a union if it is equal to any of its options.

=item comparison

A number is greater than a union if it is greater than all its options.

A number is less than a union if it is less than all its options.

=item union intersection

An intersection (C<&>) with a union is commutted across all options.  In other
words:

 (a | b | c) & d  ==yields==> ((a & d) | (b & d) | (c & d))

Options that have no intersection with the new element are dropped.  The
intersection of a constant number and a union yields that number, if the number
was in the union's ranges and otherwise yields nothing.

=back

=head1 TODO

Who knows.  Collapsing overlapping options, probably.

=head1 AUTHOR

Ricardo Signes <rjbs@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2004 by Ricardo Signes.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut
