// bslmf_removereference.h -*-C++-*-
#ifndef INCLUDED_BSLMF_REMOVEREFERENCE
#define INCLUDED_BSLMF_REMOVEREFERENCE
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
//@PURPOSE: Provide a meta-function for stripping reference-ness from types.
//
//@CLASSES:
// bsl::remove_reference: standard meta-function for stripping reference-ness
// bsl::remove_reference_t: alias to the return type of the meta-function
// bslmf::RemoveReference: meta-function for stripping reference-ness
//
//@SEE_ALSO: bslmf_addreference
//
//@DESCRIPTION: This component defines two meta-functions,
// 'bsl::remove_reference' and 'BloombergLP::bslmf::RemoveReference', both of
// which may be used to strip reference-ness (including both lvalue and rvalue
// reference-ness, if the latter is supported by the compiler) from a type.
//
// 'bsl::remove_reference' meets the requirements of the 'remove_reference'
// template defined in the C++11 standard [meta.trans.ref], while
// 'bslmf::RemoveReference' was devised before 'remove_reference' was
// standardized.
//
// The two meta-functions are functionally equivalent. The major difference
// between them is that the result for 'bsl::remove_reference' is indicated by
// the class member 'type', while the result for 'bslmf::RemoveReference' is
// indicated by the class member 'Type'.
//
// Note that 'bsl::remove_reference' should be preferred over
// 'bslmf::RemoveReference', and in general, should be used by new components.
//
///Usage
///-----
// In this section we show intended use of this component.
//
///Example 1: Remove Reference-ness of Types
///- - - - - - - - - - - - - - - - - - - - -
// Suppose that we want to remove the reference-ness of a set of types.
//
// Now, remove the reference-ness of a set of types using
// 'bsl::remove_reference' and verify that the returned type has any
// reference-ness removed:
//..
// assert(true ==
// (bsl::is_same<bsl::remove_reference<int& >::type, int >::value));
// assert(false ==
// (bsl::is_same<bsl::remove_reference<int& >::type, int&>::value));
// assert(true ==
// (bsl::is_same<bsl::remove_reference<int >::type, int >::value));
//#if defined(BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES)
// assert(true ==
// (bsl::is_same<bsl::remove_reference<int&&>::type, int >::value));
//#endif
//..
// Finally, if the current compiler supports alias templates C++11 feature, we
// remove reference-ness from a set of types using 'bsl::remove_reference_t'
// and verify that the resulting type has any reference-ness removed:
//..
//#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
// assert(true ==
// (bsl::is_same<bsl::remove_reference_t<int& >, int >::value));
// assert(false ==
// (bsl::is_same<bsl::remove_reference_t<int& >, int&>::value));
// assert(true ==
// (bsl::is_same<bsl::remove_reference_t<int >, int >::value));
//#if defined(BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES)
// assert(true ==
// (bsl::is_same<bsl::remove_reference_t<int&&>, int >::value));
//#endif
//#endif
//..
// Note that rvalue reference is a feature introduced in the C++11 standard and
// may not be supported by all compilers.
//
// Also note, that the 'bsl::remove_reference_t' avoids the '::type' suffix and
// 'typename' prefix when we want to use the result of the
// 'bsl::remove_reference' meta-function in templates.
#include <bslscm_version.h>
#include <bsls_compilerfeatures.h>
// =======================
// struct remove_reference
// =======================
namespace bsl {
template <class t_TYPE>
struct remove_reference {
// This 'struct' template implements the 'remove_reference' meta-function
// defined in the C++11 standard [meta.trans.ref], providing an alias,
// 'type', that returns the result. 'type' has the same type as the
// (template parameter) 't_TYPE' except with reference-ness removed. Note
// that this generic default template provides a 'type' that is an alias to
// 't_TYPE' for when 't_TYPE' is not a reference. A template
// specialization is provided (below) that removes reference-ness for when
// 't_TYPE' is a reference.
typedef t_TYPE type;
// This 'typedef' is an alias to the (template parameter) 't_TYPE'.
};
template <class t_TYPE>
struct remove_reference<t_TYPE&> {
// This partial specialization of 'bsl::remove_reference', for when the
// (template parameter) 't_TYPE' is an rvalue reference, provides a
// 'typedef', 'type', that has reference-ness of 't_TYPE' removed.
typedef t_TYPE type;
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE' except with the reference-ness removed.
};
#if defined(BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES)
template <class t_TYPE>
struct remove_reference<t_TYPE&&> {
// This partial specialization of 'bsl::remove_reference', for when the
// (template parameter) 't_TYPE' is a reference, provides a 'typedef',
// 'type', that has reference-ness of 't_TYPE' removed.
typedef t_TYPE type;
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE' except with the reference-ness removed.
};
#endif
#if defined(BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES)
// ALIASES
template <class t_TYPE>
using remove_reference_t = typename remove_reference<t_TYPE>::type;
// 'remove_reference_t' is an alias to the return type of the
// 'bsl::remove_reference' meta-function. Note, that the
// 'remove_reference_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
namespace BloombergLP {
namespace bslmf {
// ======================
// struct RemoveReference
// ======================
template <class t_TYPE>
struct RemoveReference {
// This 'struct' template implements a meta-function to remove the
// reference-ness from the (template parameter) 't_TYPE'. Note that
// although this 'struct' is functionally equivalent to
// 'bsl::remove_reference', the use of 'bsl::remove_reference' should be
// preferred.
typedef typename bsl::remove_reference<t_TYPE>::type Type;
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE' except with any reference-ness removed.
};
} // close package namespace
} // close enterprise namespace
#ifndef BDE_OPENSOURCE_PUBLICATION // BACKWARD_COMPATIBILITY
// ============================================================================
// BACKWARD COMPATIBILITY
// ============================================================================
#ifdef bslmf_RemoveReference
#undef bslmf_RemoveReference
#endif
#define bslmf_RemoveReference bslmf::RemoveReference
// This alias is defined for backward compatibility.
#endif // BDE_OPENSOURCE_PUBLICATION -- BACKWARD_COMPATIBILITY
#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 ----------------------------------