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Diffstat (limited to 'include/std/util/traits/impl/has_comparison.H')
| -rw-r--r-- | include/std/util/traits/impl/has_comparison.H | 135 |
1 files changed, 0 insertions, 135 deletions
diff --git a/include/std/util/traits/impl/has_comparison.H b/include/std/util/traits/impl/has_comparison.H deleted file mode 100644 index 61eae94c..00000000 --- a/include/std/util/traits/impl/has_comparison.H +++ /dev/null @@ -1,135 +0,0 @@ -/* IBM_PROLOG_BEGIN_TAG */ -/* This is an automatically generated prolog. */ -/* */ -/* $Source: src/include/util/traits/impl/has_comparison.H $ */ -/* */ -/* OpenPOWER HostBoot Project */ -/* */ -/* COPYRIGHT International Business Machines Corp. 2012,2014 */ -/* */ -/* Licensed under the Apache License, Version 2.0 (the "License"); */ -/* you may not use this file except in compliance with the License. */ -/* You may obtain a copy of the License at */ -/* */ -/* http://www.apache.org/licenses/LICENSE-2.0 */ -/* */ -/* Unless required by applicable law or agreed to in writing, software */ -/* distributed under the License is distributed on an "AS IS" BASIS, */ -/* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or */ -/* implied. See the License for the specific language governing */ -/* permissions and limitations under the License. */ -/* */ -/* IBM_PROLOG_END_TAG */ - -/** @file has_comparison.H - * - * Defines the guts of a has_foo<T> template where 'foo' is a binary - * comparison operator on a type T. This template can be used for - * template meta-programming purposes. - * - * The macros UTIL_COMPARISON_OPERATOR and UTIL_COMPARISON_OPERATOR_NAME - * can be defined to create a template. For instance (<, lessthan) will - * create a template has_lessthan that allows determination to be made on - * if T has a valid < operator. - * - * This file purposefully omits an include-guard to allow multiple templates - * to be defined for all the various comparison operators. - * - * Notice that a heavy dose of SFINAE techniques follow. - */ - -// Ensure UTIL_COMPARISON_OPERATOR has been defined. -#ifndef UTIL_COMPARISON_OPERATOR - #error Comparison operator is not defined. -#endif - -// Ensure UTIL_COMPARISON_OPERATOR_NAME has been defined. -#ifndef UTIL_COMPARISON_OPERATOR_NAME - #error Comparison operator name is not defined. -#endif - -// Macro magic to make well-formed variable names from existing #defines. -#define __UTIL_TRAIT_COMPARISON_MAKENAME(X,Y) X ## Y -#define _UTIL_TRAIT_COMPARISON_MAKENAME(X,Y) \ - __UTIL_TRAIT_COMPARISON_MAKENAME(X,Y) -#define UTIL_TRAIT_COMPARISON_MAKENAME(X) \ - _UTIL_TRAIT_COMPARISON_MAKENAME(X,\ - UTIL_COMPARISON_OPERATOR_NAME) - -namespace Util -{ - -// Creates a namespace of the form Util::__Util_Trait_Impl_OPERATOR_NAME to -// hide the template implementation in. -namespace UTIL_TRAIT_COMPARISON_MAKENAME(__Util_Trait_Impl_) -{ - // If "T op S" is valid, it is going to return a type R. If it is not - // valid, we still need it to compile cleanly. So what we do is - // create a type (convert_from_any_type) that causes implicit type - // conversion from any other type. We ensure that the operator against - // convert_from_any_type returns a special type (bad_type). - // - // If "T op S" is valid then the implicit type conversion to - // convert_from_any_type will not happen because the native "T op S" takes - // precidence. So "T op S" has type not equal to bad_type. If "T op S" - // is invalid then the implicit type conversion will cause "T op S" to have - // type bad_type. - - struct bad_type {}; - struct convert_from_any_type - { - template <class C> convert_from_any_type(C const&); - }; - bad_type operator UTIL_COMPARISON_OPERATOR (const convert_from_any_type&, - const convert_from_any_type&); - - - // Now, "T op S" is going to return either bad_type or something else. We - // define a function 'has_comparison' that returns a character array of - // different size based on the input parameter type. Then the "sizeof" - // can be used to tell if "T op S" returns bad_type or something else. - // - // The only additional oddity is the get_instance function. Since some - // classes cannot be directly constructed, this is a level of indirection - // to get a type of T and S to apply the operator against. - template <typename _T, typename _S, typename _R> - struct UTIL_TRAIT_COMPARISON_MAKENAME(has_) - { - typedef char yes[1]; - typedef char no[2]; - - static no& has_comparison(bad_type); - static yes& has_comparison(_R); - - template <typename C> static C& get_instance(); - - static const bool value = - sizeof(has_comparison(get_instance<_T>() UTIL_COMPARISON_OPERATOR - get_instance<_S>())) == sizeof(yes); - }; - -}; - - -// Since the implementation was hidden in a __Util_Trait_Impl_OPERATOR_NAME -// namespace, we expose just the main comparison class (with the value variable) -// by defining a class in the Traits namespace that inherits from the one in -// the __Util_Trait_Impl_OPERATOR_NAME namespace. -namespace Traits -{ - template <typename _T, typename _S = _T, - typename _R = typename - UTIL_TRAIT_COMPARISON_MAKENAME(Util::__Util_Trait_Impl_):: - convert_from_any_type> - struct UTIL_TRAIT_COMPARISON_MAKENAME(has_) : - public UTIL_TRAIT_COMPARISON_MAKENAME(Util::__Util_Trait_Impl_):: - UTIL_TRAIT_COMPARISON_MAKENAME(has_)<_T,_S,_R> - {}; -}; - -}; - -#undef __UTIL_TRAIT_COMPARISON_MAKENAME -#undef _UTIL_TRAIT_COMPARISON_MAKENAME -#undef UTIL_TRAIT_COMPARISON_MAKENAME - |
