// bslmf_removecvref.h -*-C++-*- #ifndef INCLUDED_BSLMF_REMOVECVREF #define INCLUDED_BSLMF_REMOVECVREF #include <bsls_ident.h> BSLS_IDENT("$Id: $") //@PURPOSE: Provide a meta-func for removing reference-ness and cv-qualifiers. // //@CLASSES: // bsl::remove_cvref: meta-func for removing reference-ness and cv-qualifiers // bsl::remove_cvref_t: alias to the return type of the meta-function // //@SEE_ALSO: bslmf_removecv, bslmf_removereference // //@DESCRIPTION: This component defines a meta-function, 'bsl::remove_cvref', // and declares a 'bsl::remove_cvref_t' alias to the return type of the // 'bsl::remove_cvref', that may be used to strip reference-ness (including // both lvalue and rvalue reference-ness, if the latter is supported by the // compiler) and to remove any top-level cv-qualifiers ('const'-qualifier and // 'volatile'-qualifier) from a type. // // 'bsl::remove_cvref' and 'bsl::remove_cvref_t' meet the requirements of the // 'remove_cvref' template defined in the C++20 standard [meta.trans.other]. // ///Usage ///----- // In this section we show intended use of this component. // ///Example 1: Removing the CV-Qualifiers and Reference-ness of a Type /// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - // Suppose that we want to remove the cv-qualifiers from a particular type. // // First, we create two 'typedef's -- a 'const'-qualified and // 'volatile'-qualified reference type ('MyCvRefType') and the same type // without the cv-qualifiers and reference-ness ('MyType'): //.. // typedef const volatile int& MyCvRefType; // typedef int MyType; //.. // Now, we remove the cv-qualifiers from 'MyCvRefType' and its reference-ness // using 'bsl::remove_cvref' and verify that the resulting type is the same as // 'MyType': //.. // assert(true == (bsl::is_same<bsl::remove_cvref<MyCvRefType>::type, // MyType>::value)); //.. // Finally, if the current compiler supports alias templates C++11 feature, we // remove a 'const'-qualifier, 'volatile'-qualifier and its reference-ness from // 'MyCvRefType' using 'bsl::remove_cvref_t' and verify that the resulting type // is the same as 'MyType': //.. //#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES // assert( // true == // (bsl::is_same<bsl::remove_cvref_t<MyCvRefType>, MyType>::value)); //#endif //.. #include <bslscm_version.h> #include <bslmf_removecv.h> #include <bslmf_removereference.h> #include <bsls_compilerfeatures.h> namespace bsl { // =================== // struct remove_cvref // =================== template <class t_TYPE> struct remove_cvref { // This 'struct' template implements the 'remove_cvref' meta-function // defined in the C++20 standard [meta.trans.other], providing an alias, // 'type', that returns the result. 'type' has the same type as the // (template parameter) 't_TYPE' except that its reference-ness has been // stripped and any top-level cv-qualifiers have been removed. // PUBLIC TYPES typedef typename bsl::remove_cv< typename bsl::remove_reference<t_TYPE>::type>::type type; // This 'typedef' is an alias to the same type as the (template // parameter) 't_TYPE' except that its reference-ness has been stripped // and any top-level cv-qualifier has been removed. }; #ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES // ALIASES template <class t_TYPE> using remove_cvref_t = typename remove_cvref<t_TYPE>::type; // 'remove_cvref_t' is an alias to the return type of the // 'bsl::remove_cvref' meta-function. Note, that the 'remove_cvref_t' // avoids the '::type' suffix and 'typename' prefix when we want to use the // result of the meta-function in templates. #endif // BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES } // close namespace bsl #endif // ---------------------------------------------------------------------------- // Copyright 2021 Bloomberg Finance L.P. // // 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. // ----------------------------- END-OF-FILE ----------------------------------