/ 
Language-MuldisD-0.23.0
/ Language::MuldisD::Ext::Ordered

NAME

Language::MuldisD::Ext::Ordered - Muldis D extension for generic ordered-sensitive operators

VERSION

This document is Language::MuldisD::Ext::Ordered version 0.20.0.

PREFACE

This document is part of the Muldis D language specification, whose root document is Language::MuldisD; you should read that root document before you read this one, which provides subservient details.

DESCRIPTION

Muldis D has a mandatory core set of system-defined (eternally available) entities, which is referred to as the Muldis D core or the core; they are the minimal entities that all Muldis D implementations need to provide; they are mutually self-describing and are used to bootstrap the language; any entities outside the core, called Muldis D extensions, are non-mandatory and are defined in terms of the core or each other, but the reverse isn't true.

This current Ordered document describes the system-defined Muldis D Ordered Extension, which consists of generic operators that are sensitive to an ordering of a type's values, and are used for such things as list sorting or quota queries or determining before/after/min/max/between/etc. They can potentially be used with values of any data type as long as said data type is either inherently ordered or or has an order-determination operator defined for them.

This current document does not describe the polymorphic operators that all types, or some types including core types, have defined over them; said operators are defined once for all types in Language::MuldisD::Core.

This documentation is pending.

SYSTEM-DEFINED ORDER-CONCERNING FUNCTIONS

These functions are applicable to values of potentially any data type, those which have a comparison or such function defined for them. They provide a common syntax for sort-related functionality, though technically every type having these functions is re-implementing its own version. If values of an ordered data type can conceivably be sorted using multiple criteria (such as different text collations), then these functions just represent the default criteria; any additional criteria are represented by additional functions declared for just the types they apply to.

function sys.Ordered.Ord.is_before result Bool params { topic(Universal), other(Universal) }

This function results in Bool:true iff its 2 arguments are non-identical and the value of the topic argument is considered to come before the value of the other argument when the 2 values are arranged in order (as defined by the type); it results in Bool:false otherwise. This function's arguments must be of compatible declared types; in this case, 2 declared types are compatible iff they are both subtypes of a common scalar type that declares a comparison function for itself. Note that is_before is considered the only fundamental ordered-specific operator, and all others are defined over it plus is_identical.

function sys.Ordered.Ord.is_not_before result Bool params { topic(Universal), other(Universal) }

This function is exactly the same as sys.Ordered.Ord.is_before except that it results in the opposite boolean value when given the same arguments. (It could alternately be called "is after or is identical".)

function sys.Ordered.Ord.is_inside_range result Bool params { topic(Universal), min(Universal), max(Universal), min_is_inside(Bool), max_is_inside(Bool) }

This function results in Bool:true iff its topic argument is within the range whose bounds are defined by its min and max arguments. If min_is_inside or max_is_inside are Bool:true, then topic is considered to be within the range if it is equal to min or max, respectively. This function's arguments must be of compatible declared types as per sys.Ordered.Ord.is_before. This function will fail if max is before min.

function sys.Ordered.Ord.is_outside_range result Bool params { topic(Universal), min(Universal), max(Universal), min_is_inside(Bool), max_is_inside(Bool) }

This function is exactly the same as sys.Ordered.Ord.is_inside_range except that it results in the opposite boolean value when given the same arguments.

function sys.Ordered.Ord.min result Universal params { topic(Set) }

This function is a reduction operator that recursively takes each pair of its N input element values and picks the minimum of the 2 (a process which is both commutative and associative) until just one is left, which is the function's result. If topic has zero values, then min results in the result type's concept of positive infinity, which is the identity value for min. This function will fail on a topic of zero values if the result type's concept of positive infinity is impossible or impractically large to represent, such as with the infinite Text type.

function sys.Ordered.Ord.max result Universal params { topic(Set) }

This function is exactly the same as sys.Ordered.Ord.min except that it results in the maximum input element value rather than the minimum one, and its identity value is the result type's concept of negative infinity.

function sys.Ordered.Ord.maybe_min result Maybe params { topic(Set) }

This function is exactly the same as sys.Ordered.Ord.min except that it results in a Maybe of what is otherwise the result type, and that result has zero elements if the argument has zero elements.

function sys.Ordered.Ord.maybe_max result Maybe params { topic(Set) }

This function is to sys.Ordered.Ord.max as sys.Ordered.Ord.maybe_min is to sys.Ordered.Ord.min.

SEE ALSO

Go to Language::MuldisD for the majority of distribution-internal references, and Language::MuldisD::SeeAlso for the majority of distribution-external references.

AUTHOR

Darren Duncan (perl@DarrenDuncan.net)

LICENSE AND COPYRIGHT

This file is part of the formal specification of the Muldis D language.

Muldis D is Copyright © 2002-2008, Darren Duncan.

See the LICENSE AND COPYRIGHT of Language::MuldisD for details.

ACKNOWLEDGEMENTS

The ACKNOWLEDGEMENTS in Language::MuldisD apply to this file too.