--- /dev/null
+package MooseX::Types::Parameterizable;
+
+use 5.008;
+
+our $VERSION = '0.01';
+$VERSION = eval $VERSION;
+
+use Moose::Util::TypeConstraints;
+use MooseX::Meta::TypeConstraint::Parameterizable;
+use MooseX::Types -declare => [qw(Parameterizable)];
+
+=head1 NAME
+
+MooseX::Types::Parameterizable - Create your own Parameterizable Types.
+
+=head1 SYNOPSIS
+
+Within your L<MooseX::Types> declared library module:
+
+ use MooseX::Types::Parameterizable qw(Parameterizable);
+
+ subtype Set,
+ as class_type("Set::Scalar");
+
+ subtype UniqueInt,
+ as Parameterizable[Int, Set],
+ where {
+ my ($int, $set) = @_;
+ return !$set->has($int);
+ };
+
+ subtype PositiveSet,
+ as Set,
+ where {
+ my ($set) = @_;
+ return !grep {$_ <0 } $set->members;
+ };
+
+ subtype PositiveUniqueInt,
+ as UniqueInt[PositiveSet];
+
+ my $set = Set::Scalar->new(1,2,3);
+
+ UniqueInt([$set])->check(100); ## Okay, 100 isn't in (1,2,3)
+ UniqueInt([$set])->check(-99); ## Okay, -99 isn't in (1,2,3)
+ UniqueInt([$set])->check(2); ## Not OK, 2 is in (1,2,3)
+
+ PositiveUniqueInt([$set])->check(100); ## Okay, 100 isn't in (1,2,3)
+ PositiveUniqueInt([$set])->check(-99); ## Not OK, -99 not Positive Int
+ PositiveUniqueInt([$set])->check(2); ## Not OK, 2 is in (1,2,3)
+
+ my $negative_set = Set::Scalar->new(-1,-2,-3);
+
+ UniqueInt([$negative_set])->check(100); ## Throws exception
+
+=head1 DESCRIPTION
+
+A L<MooseX::Types> library for creating parameterizable types. A parameterizable type
+constraint for all intents and uses is a subclass of a parent type, but adds a
+secondary type parameter which is available to constraint callbacks (such as
+inside the 'where' clause) or in the coercions.
+
+This allows you to create a type that has additional runtime advice, such as a
+set of numbers within which another number must be unique, or allowable ranges
+for a integer, such as in:
+
+ subtype Range,
+ as Dict[max=>Int, min=>Int],
+ where {
+ my ($range) = @_;
+ return $range->{max} > $range->{min};
+ };
+
+ subtype RangedInt,
+ as Parameterizable[Int, Range],
+ where {
+ my ($value, $range) = @_;
+ return ($value >= $range->{min} &&
+ $value <= $range->{max});
+ };
+
+ RangedInt([{min=>10,max=>100}])->check(50); ## OK
+ RangedInt([{min=>50, max=>75}])->check(99); ## Not OK, 99 exceeds max
+
+This throws a hard Moose exception. You'll need to capture it in an eval or
+related exception catching system (see L<TryCatch>).
+
+ RangedInt([{min=>99, max=>10}])->check(10); ## Not OK, not a valid Range!
+
+If you can't accept a hard exception here, you'll need to test the constraining
+values first, as in:
+
+ my $range = {min=>99, max=>10};
+ if(my $err = Range->validate($range)) {
+ ## Handle #$err
+ } else {
+ RangedInt($range)->check(99);
+ }
+
+Please note that for ArrayRef or HashRef parameterizable type constraints, as in the
+example above, as a convenience we automatically ref the incoming type
+parameters, so that the above could also be written as:
+
+ RangedInt([min=>10,max=>100])->check(50); ## OK
+ RangedInt([min=>50, max=>75])->check(99); ## Not OK, 99 exceeds max
+ RangedInt([min=>99, max=>10])->check(10); ## Exception, not a valid Range!
+
+This is the preferred syntax, as it improve readability and adds to the
+conciseness of your type constraint declarations. An exception wil be thrown if
+your type parameters don't match the required reference type.
+
+Also not that if you 'chain' parameterization results with a method call like:
+
+ TypeConstraint([$ob])->method;
+
+You need to have the "(...)" around the ArrayRef in the Type Constraint
+parameters. This seems to have something to do with the precendent level of
+"->". Patches or thoughts welcomed. You only need to do this in the above
+case which I imagine is not a very common case.
+
+==head2 Subtyping a Parameterizable type constraints
+
+When subclassing a parameterizable type you must be careful to match either the
+required type parameter type constraint, or if re-parameterizing, the new
+type constraints are a subtype of the parent. For example:
+
+ subtype RangedInt,
+ as Parameterizable[Int, Range],
+ where {
+ my ($value, $range) = @_;
+ return ($value >= $range->{min} &&
+ $value =< $range->{max});
+ };
+
+Example subtype with additional constraints:
+
+ subtype PositiveRangedInt,
+ as RangedInt,
+ where {
+ shift >= 0;
+ };
+
+Or you could have done the following instead:
+
+ ## Subtype of Int for positive numbers
+ subtype PositiveInt,
+ as Int,
+ where {
+ my ($value, $range) = @_;
+ return $value >= 0;
+ };
+
+ ## subtype Range to re-parameterize Range with subtypes
+ subtype PositiveRange,
+ as Range[max=>PositiveInt, min=>PositiveInt];
+
+ ## create subtype via reparameterizing
+ subtype PositiveRangedInt,
+ as RangedInt[PositiveRange];
+
+Notice how re-parameterizing the parameterizable type 'RangedInt' works slightly
+differently from re-parameterizing 'PositiveRange' Although it initially takes
+two type constraint values to declare a parameterizable type, should you wish to
+later re-parameterize it, you only use a subtype of the second type parameter
+(the parameterizable type constraint) since the first type constraint sets the parent
+type for the parameterizable type. In other words, given the example above, a type
+constraint of 'RangedInt' would have a parent of 'Int', not 'Parameterizable' and for
+all intends and uses you could stick it wherever you'd need an Int.
+
+ subtype NameAge,
+ as Tuple[Str, Int];
+
+ ## re-parameterized subtypes of NameAge containing a Parameterizable Int
+ subtype NameBetween18and35Age,
+ as NameAge[
+ Str,
+ PositiveRangedInt[min=>18,max=>35],
+ ];
+
+One caveat is that you can't stick an unparameterized parameterizable type inside a
+structure, such as L<MooseX::Types::Structured> since that would require the
+ability to convert a 'containing' type constraint into a parameterizable type, which
+is a capacity we current don't have.
+
+=head2 Coercions
+
+Parameterizable types have some limited support for coercions. Several things must
+be kept in mind. The first is that the coercion targets the type constraint
+which is being made parameterizable, Not the parameterizable type. So for example if you
+create a Parameterizable type like:
+
+ subtype RequiredAgeInYears,
+ as Int;
+
+ subtype PersonOverAge,
+ as Parameterizable[Person, RequiredAgeInYears]
+ where {
+ my ($person, $required_years_old) = @_;
+ return $person->years_old > $required_years_old;
+ }
+
+This would validate the following:
+
+ my $person = Person->new(age=>35);
+ PersonOverAge([18])->check($person);
+
+You can then apply the following coercion
+
+ coerce PersonOverAge,
+ from Dict[age=>int],
+ via {Person->new(%$_)},
+ from Int,
+ via {Person->new(age=>$_)};
+
+This coercion would then apply to all the following:
+
+ PersonOverAge([18])->check(30); ## via the Int coercion
+ PersonOverAge([18])->check({age=>50}); ## via the Dict coercion
+
+However, you are not allowed to place coercions on parameterizable types that have
+had their constraining value filled, nor subtypes of such. For example:
+
+ coerce PersonOverAge[18],
+ from DateTime,
+ via {$_->years};
+
+That would generate a hard exception. This is a limitation for now until I can
+devise a smarter way to cache the generated type constraints. However, I doubt
+it will be a significant limitation, since the general use case is supported.
+
+Lastly, the constraining value is available in the coercion in much the same way
+it is available to the constraint.
+
+ ## Create a type constraint where a Person must be in the set
+ subtype PersonInSet,
+ as Parameterizable[Person, PersonSet],
+ where {
+ my ($person, $person_set) = @_;
+ $person_set->find($person);
+ }
+
+ coerce PersonInSet,
+ from HashRef,
+ via {
+ my ($hashref, $person_set) = @_;
+ return $person_set->create($hash_ref);
+ };
+
+=head2 Recursion
+
+ TBD
+
+=head1 TYPE CONSTRAINTS
+
+This type library defines the following constraints.
+
+=head2 Parameterizable[ParentTypeConstraint, ParameterizableValueTypeConstraint]
+
+Create a subtype of ParentTypeConstraint with a dependency on a value that can
+pass the ParameterizableValueTypeConstraint. If ParameterizableValueTypeConstraint is empty
+we default to the 'Any' type constraint (see L<Moose::Util::TypeConstraints>).
+
+This creates a type constraint which must be further parameterized at later time
+before it can be used to ->check or ->validate a value. Attempting to do so
+will cause an exception.
+
+=cut
+
+Moose::Util::TypeConstraints::get_type_constraint_registry->add_type_constraint(
+ MooseX::Meta::TypeConstraint::Parameterizable->new(
+ name => 'MooseX::Types::Parameterizable::Parameterizable',
+ parent => find_type_constraint('Any'),
+ constraint => sub {1},
+ )
+);
+
+=head1 AUTHOR
+
+John Napiorkowski, C<< <jjnapiork@cpan.org> >>
+
+=head1 COPYRIGHT & LICENSE
+
+This program is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
+
+=cut
+
+1;
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