use strict;
use warnings;
# ABSTRACT: a tolerance "m +/- n"

package
  Number::Tolerant::Type::plus_or_minus;
use parent qw(Number::Tolerant::Type);

sub construct { shift;
  {
    value => $_[0],
    variance => $_[1],
    min => $_[0] - $_[1],
    max => $_[0] + $_[1]
  }
}

sub parse {
  my ($self, $string, $factory) = @_;

  my $number = $self->number_re;

  return $factory->new("$1", 'plus_or_minus', "$2")
    if $string =~ m!\A($number)\s*\+/-\s*($number)\z!;
  return;
}

sub stringify { "$_[0]->{value} +/- $_[0]->{variance}"  }

sub valid_args {
  my $self = shift;

  return unless 3 == grep { defined } @_;
  return unless $_[1] eq 'plus_or_minus';

  return unless defined (my $base = $self->normalize_number($_[0]));
  return unless defined (my $var  = $self->normalize_number($_[2]));

  return ($base, $var);
}

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

Number::Tolerant::Type::plus_or_minus - a tolerance "m +/- n"

=head1 VERSION

version 1.708

=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
