// bslmf_addcv.h -*-C++-*- #ifndef INCLUDED_BSLMF_ADDCV #define INCLUDED_BSLMF_ADDCV #include <bsls_ident.h> BSLS_IDENT("$Id: $") //@PURPOSE: Provide a meta-function for adding top-level cv-qualifiers. // //@CLASSES: // bsl::add_cv: meta-function for adding top-level cv-qualifiers // bsl::add_cv_t: alias to the return type of the 'bsl::add_cv' meta-function // //@SEE_ALSO: bslmf_removecv // //@DESCRIPTION: This component defines a meta-function, 'bsl::add_cv' and // declares an 'bsl::add_cv_t' alias to the return type of the 'bsl::add_cv', // that may be used to add a top-level 'const'-qualifier and a top-level // 'volatile'-qualifier to a type if it is not a reference type, nor a function // type, nor already 'const'-qualified and 'volatile'-qualified at the // top-level. // // 'bsl::add_cv' and 'bsl::add_cv_t' meet the requirements of the 'add_cv' // template defined in the C++11 standard [meta.trans.cv]. // ///Usage ///----- // In this section we show intended use of this component. // ///Example 1: Adding a 'const'-Qualifier and a 'volatile'-Qualifier to a Type /// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - // Suppose that we want to add a 'const'-qualifier and a 'volatile'-qualifier // to a particular type. // // First, we create two 'typedef's -- a 'const'-qualified and // 'volatile'-qualified type ('MyCvType') and the same type without the // cv-qualifiers ('MyType'): //.. // typedef int MyType; // typedef const volatile int MyCvType; //.. // Now, we add a 'const'-qualifier and a 'volatile'-qualifier to 'MyType' using // 'bsl::add_cv' and verify that the resulting type is the same as 'MyCvType': //.. // assert(true == (bsl::is_same<bsl::add_cv<MyType>::type, MyCvType>::value)); //.. // Finally, if the current compiler supports alias templates C++11 feature, we // add a 'const'-qualifier and a 'volatile'-qualifier to 'MyType' using // 'bsl::add_cv_t' and verify that the resulting type is the same as // 'MyCvType': //.. //#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES // assert(true == (bsl::is_same<bsl::add_cv_t<MyType>, MyCvType>::value)); //#endif //.. // Note, that the 'bsl::add_cv_t' avoids the '::type' suffix and 'typename' // prefix when we want to use the result of the 'bsl::add_cv' meta-function in // templates. #include <bslscm_version.h> #include <bslmf_addconst.h> #include <bslmf_addvolatile.h> #include <bsls_compilerfeatures.h> namespace bsl { // ============= // struct add_cv // ============= template <class t_TYPE> struct add_cv { // This 'struct' template implements the 'add_cv' meta-function defined in // the C++11 standard [meta.trans.cv], providing an alias, 'type', that // returns the result. If the (template parameter) 't_TYPE' is not a // reference type, nor a function type, nor already 'const'-qualified and // 'volatile'-qualified at the top-level, then 'type' is an alias to // 't_TYPE' with a top-level 'const'-qualifier and a 'volatile'-qualifier // added; otherwise, 'type' is an alias to 't_TYPE'. // PUBLIC TYPES typedef typename add_const<typename add_volatile<t_TYPE>::type>::type type; // This 'typedef' is an alias to the (template parameter) 't_TYPE' with // a top-level 'const'-qualifier and 'volatile'-qualifier added if // 't_TYPE' is not a reference type, nor a function type, nor already // 'const'-qualified and 'volatile'-qualified at the top-level; // otherwise, 'type' is an alias to 't_TYPE'. }; #ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES // ALIASES template <class t_TYPE> using add_cv_t = typename add_cv<t_TYPE>::type; // 'add_cv_t' is an alias to the return type of the 'bsl::add_cv' // meta-function. Note, that the 'add_cv_t' avoids the '::type' suffix and // 'typename' prefix when we want to use the result of the 'bsl::add_cv' in // templates. #endif // BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES } // close namespace bsl #endif // ---------------------------------------------------------------------------- // Copyright 2013 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 ----------------------------------