185 lines
7.8 KiB
C++
185 lines
7.8 KiB
C++
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// (C) Copyright Edward Diener 2019
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// Use, modification and distribution are subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt).
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#if !defined(BOOST_TTI_HAS_ENUM_HPP)
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#define BOOST_TTI_HAS_ENUM_HPP
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#include <boost/config.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/tti/gen/has_enum_gen.hpp>
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#include <boost/tti/gen/namespace_gen.hpp>
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#include <boost/tti/detail/denum.hpp>
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#include <boost/tti/detail/ddeftype.hpp>
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/*
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The succeeding comments in this file are in doxygen format.
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*/
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/** \file
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*/
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/// A macro which expands to a metafunction which tests whether an inner enum with a particular name exists.
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/**
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BOOST_TTI_TRAIT_HAS_ENUM is a macro which expands to a metafunction.
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The metafunction tests whether an inner enum with a particular name exists
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and, optionally, whether an MPL lambda expression invoked with the inner enum
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is true or not. The macro takes the form of BOOST_TTI_TRAIT_HAS_ENUM(trait,name) where
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trait = the name of the metafunction <br/>
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name = the name of the inner enum. The name can be that of an enum or, in C++11 on up, an enum class.
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BOOST_TTI_TRAIT_HAS_ENUM generates a metafunction called "trait" where 'trait' is the macro parameter.
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@code
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_U>
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struct trait
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{
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static const value = unspecified;
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typedef mpl::bool_<true-or-false> type;
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};
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The metafunction types and return:
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BOOST_TTI_TP_T = the enclosing type in which to look for our 'name'.
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The enclosing type can be a class, struct, or union.
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BOOST_TTI_TP_U = (optional) An optional template parameter, defaulting to a marker type.
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If specified it is an MPL lambda expression which is invoked
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with the inner enum found and must return a constant boolean
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value.
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returns = 'value' depends on whether or not the optional BOOST_TTI_TP_U is specified.
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If BOOST_TTI_TP_U is not specified, then 'value' is true if the 'name' enum
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exists within the enclosing type BOOST_TTI_TP_T; otherwise 'value' is false.
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If BOOST_TTI_TP_U is specified , then 'value' is true if the 'name' enum exists
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within the enclosing type BOOST_TTI_TP_T and the MPL lambda expression as specified
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by BOOST_TTI_TP_U, invoked by passing the actual inner enum of 'name', returns
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a 'value' of true; otherwise 'value' is false.
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The action taken with BOOST_TTI_TP_U occurs only when the 'name' enum exists
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within the enclosing type BOOST_TTI_TP_T.
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@endcode
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Example usage:
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@code
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BOOST_TTI_TRAIT_HAS_ENUM(LookFor,MyType) generates the metafunction LookFor in the current scope
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to look for an inner enum called MyType.
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LookFor<EnclosingType>::value is true if MyType is an inner enum of EnclosingType, otherwise false.
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LookFor<EnclosingType,ALambdaExpression>::value is true if MyType is an inner enum of EnclosingType
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and invoking ALambdaExpression with the inner enum returns a value of true, otherwise false.
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A popular use of the optional MPL lambda expression is to check whether the enum found is the same
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as another type, when the enum found is a typedef. In that case our example would be:
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LookFor<EnclosingType,boost::is_same<_,SomeOtherType> >::value is true if MyType is an inner enum
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of EnclosingType and is the same type as SomeOtherType.
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@endcode
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*/
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#define BOOST_TTI_TRAIT_HAS_ENUM(trait,name) \
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BOOST_TTI_DETAIL_TRAIT_HAS_ENUM(trait,name) \
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template \
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< \
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class BOOST_TTI_TP_T, \
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class BOOST_TTI_TP_U = BOOST_TTI_NAMESPACE::detail::deftype \
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> \
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struct trait \
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{ \
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typedef typename \
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BOOST_PP_CAT(trait,_detail_enum)<BOOST_TTI_TP_T,BOOST_TTI_TP_U>::type type; \
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BOOST_STATIC_CONSTANT(bool,value=type::value); \
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}; \
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/**/
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/// A macro which expands to a metafunction which tests whether an inner enum with a particular name exists.
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/**
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BOOST_TTI_HAS_ENUM is a macro which expands to a metafunction.
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The metafunction tests whether an inner enum with a particular name exists
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and, optionally, whether an MPL lambda expression invoked with the inner enum
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is true or not. The macro takes the form of BOOST_TTI_HAS_ENUM(name) where
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name = the name of the inner enum. The name can be that of an enum or, in C++11 on up, an enum class.
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BOOST_TTI_HAS_ENUM generates a metafunction called "has_enum_'name'" where 'name' is the macro parameter.
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@code
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_U>
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struct has_enum_'name'
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{
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static const value = unspecified;
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typedef mpl::bool_<true-or-false> type;
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};
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The metafunction types and return:
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BOOST_TTI_TP_T = the enclosing type in which to look for our 'name'.
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The enclosing type can be a class, struct, or union.
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BOOST_TTI_TP_U = (optional) An optional template parameter, defaulting to a marker type.
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If specified it is an MPL lambda expression which is invoked
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with the inner enum found and must return a constant boolean
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value.
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returns = 'value' depends on whether or not the optional BOOST_TTI_TP_U is specified.
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If BOOST_TTI_TP_U is not specified, then 'value' is true if the 'name' enum
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exists within the enclosing type BOOST_TTI_TP_T; otherwise 'value' is false.
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If BOOST_TTI_TP_U is specified, then 'value' is true if the 'name' enum exists
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within the enclosing type BOOST_TTI_TP_T and the MPL lambda expression as specified
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by BOOST_TTI_TP_U, invoked by passing the actual inner enum of 'name', returns
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a 'value' of true; otherwise 'value' is false.
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The action taken with BOOST_TTI_TP_U occurs only when the 'name' enum exists
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within the enclosing type BOOST_TTI_TP_T.
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@endcode
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Example usage:
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@code
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BOOST_TTI_HAS_ENUM(MyType) generates the metafunction has_enum_MyType in the current scope
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to look for an inner enum called MyType.
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has_enum_MyType<EnclosingType>::value is true if MyType is an inner enum of EnclosingType, otherwise false.
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has_class_MyType<EnclosingType,ALambdaExpression>::value is true if MyType is an inner enum of EnclosingType
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and invoking ALambdaExpression with the inner enum returns a value of true, otherwise false.
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A popular use of the optional MPL lambda expression is to check whether the enum found is the same
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as another type, when the enum found is a typedef. In that case our example would be:
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has_enum_MyType<EnclosingType,boost::is_same<_,SomeOtherType> >::value is true if MyType is an inner enum
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of EnclosingType and is the same type as SomeOtherType.
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@endcode
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*/
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#define BOOST_TTI_HAS_ENUM(name) \
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BOOST_TTI_TRAIT_HAS_ENUM \
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( \
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BOOST_TTI_HAS_ENUM_GEN(name), \
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name \
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) \
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/**/
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#endif // BOOST_TTI_HAS_ENUM_HPP
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