/ 
Muldis-D-0.55.0
/ Muldis::D::Ext::QSet

NAME

Muldis::D::Ext::QSet - Muldis D extension for QSet and QMaybe specific operators

VERSION

This document is Muldis::D::Ext::QSet version 0.55.0.

PREFACE

This document is part of the Muldis D language specification, whose root document is Muldis::D; 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 QSet document describes the system-defined Muldis D QSet Extension, which consists of generic operators that are specific to the QSet and QMaybe parameterized q/relation types, and said operators are short-hands for generic relational operators in the language core.

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 Muldis::D::Core.

This documentation is pending.

SYSTEM-DEFINED QUASI-/SET-CONCERNING FUNCTIONS

Each assuming parameter is optional and defaults to the zero-attribute tuple if no explicit argument is given to it.

function sys.std.QSet.is_member result Bool params { set(QSet), value(Universal) }

This function results in Bool:true iff its value argument matches the sole attribute of a q/tuple of its set argument (that is, iff conceptually value is a member of set), and Bool:false otherwise. This function will warn if its 2 arguments are incompatible as per sys.std.Core.QRelation.is_subset.

function sys.std.QSet.is_not_member result Bool params { set(QSet), value(Universal) }

This function is exactly the same as sys.std.QSet.is_member except that it results in the opposite boolean value when given the same arguments.

function sys.std.QSet.insertion result QSet params { set(QSet), value(Universal) }

This function results in a QSet that is the relational union of set and a QSet whose sole q/tuple has the sole attribute value of value; that is, conceptually the result is value inserted into set. As a trivial case, if value already exists in set, then the result is just set.

function sys.std.QSet.disjoint_insertion result QSet params { set(QSet), value(Universal) }

This function is exactly the same as sys.std.QSet.insertion except that it will fail if value already exists in set.

function sys.std.QSet.deletion result QSet params { set(QSet), value(Universal) }

This function results in a QSet that is the relational difference from set of a QSet whose sole q/tuple has the sole attribute value of value; that is, conceptually the result is value deleted from set. As a trivial case, if value already doesn't exist in set, then the result is just set.

function sys.std.QSet.reduction result Universal params { topic(QSet), func(FuncRef), assuming(QTuple)?, identity(Universal) }

This function is a generic reduction operator that recursively takes each pair of input values in topic and applies an argument-specified q/scalar or q/nonscalar value-resulting function (which is both commutative and associative) to the pair until just one input value is left, which is the result. The function to apply is named in the func argument, and that function must have 3 arguments named v1, v2, assuming; the last parameter is curried with the same-named argument of reduction, and the first 2 parameters are the 2 input q/scalar or q/nonscalar values for an invocation. If topic has zero values, then reduction results in the value given in identity. Note that identity may be changed to take a function name rather than a value, for consistency with func. This function will fail|warn if the |declared type of identity isn't a subtype of the |declared type of the sole attribute of topic.

function sys.std.QSet.maybe_reduction result QMaybe params { topic(QSet), func(FuncRef), assuming(QTuple)? }

This function is exactly the same as sys.std.QSet.reduction except that it does not take an assuming argument, and it results in a QMaybe of what is otherwise the result type, and that result has zero elements if the argument has zero elements.

function sys.std.QSet.QSet_from_wrap result set_of.QTuple params { topic(QRelation) }

This function results in a QSet whose sole attribute is q/tuple-typed and the attribute values are all the q/tuples of topic; is a short-hand for a relational wrap of all attributes of topic such that the new q/tuple-valued attribute is named value.

function sys.std.QSet.QSet_from_attr result QSet params { topic(QRelation), name(Name) }

This function results in a QSet consisting of all the values of the attribute of topic named by name. It is a short-hand for a unary projection of just the named attribute plus its renaming to value.

SYSTEM-DEFINED QUASI-/MAYBE-CONCERNING FUNCTIONS

function sys.std.QSet.QMaybe.nothing result Nothing params {}

This selector function results in the only zero-tuple QMaybe value.

function sys.std.QSet.QMaybe.single result QSingle params { value(Universal) }

This selector function results in the QMaybe value with a single q/tuple whose value attribute's value is the value argument.

function sys.std.QSet.QMaybe.attr result Universal params { topic(QSingle) }

This function results in the q/scalar or q/nonscalar value of the sole attribute of the sole q/tuple of its argument, which always exists when the argument is a QSingle.

function sys.std.QSet.QMaybe.attr_or_default result Universal params { topic(QMaybe), default(TypeRef) }

This function results in the q/scalar or q/nonscalar value of the sole attribute of the sole q/tuple of its argument, if said q/tuple exists; otherwise, it results in the default value of the q/scalar or q/nonscalar data type whose name is given in the default argument. This function is a short-hand for invoking attr_or_value with the result from invoking sys.std.Core.Universal.default.

function sys.std.QSet.QMaybe.attr_or_value result Universal params { topic(QMaybe), value(Universal) }

This function results in the q/scalar or q/nonscalar value of the sole attribute of the sole q/tuple of topic, if said q/tuple exists; otherwise, it results in value. This function will warn if the declared type of value isn't a subtype of the declared type of the attribute.

function sys.std.QSet.QMaybe.order result Order params { topic(QMaybe), other(QMaybe), treat_nothing_as_max(Bool), ord_func(OrdDetFuncRef)?, ord_assuming(QTuple)?, reverse_order_of_singles(Bool)? }

This function is a generic (total) order_determination function for QMaybe values. Iff both of its topic and other arguments are identical, this function results in Order:same. Otherwise, iff both of those 2 arguments are QSingle values, then the result of this function is the result of applying to those 2 arguments the (total) order_determination function given in its ord_func argument, as curried by its ord_assuming argument; if reverse_order_of_singles is Bool:true then sys.std.Core.Cat.Order_reverse is also applied such that the result of ord_func is reversed, and otherwise it isn't applied. Otherwise, iff topic is Nothing, this function results in Order:increase or Order:decrease respectively when treat_nothing_as_max is Bool:false (the default) or Bool:true. Otherwise (iff other is Nothing), this function results in the reverse of when only topic is Nothing. In situations where a QMaybe is used analagously to a SQL nullable value and this function is analagous to the binary comparison underlying a SQL "ORDER BY", then reverse_order_of_singles designates SQL's "ASC|DESC" and treat_nothing_as_max designates SQL's "NULLS FIRST|LAST".

SEE ALSO

Go to Muldis::D for the majority of distribution-internal references, and Muldis::D::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 Muldis::D for details.

TRADEMARK POLICY

The TRADEMARK POLICY in Muldis::D applies to this file too.

ACKNOWLEDGEMENTS

The ACKNOWLEDGEMENTS in Muldis::D apply to this file too.