// bslmf_removeconst.h -*-C++-*-
#ifndef INCLUDED_BSLMF_REMOVECONST
#define INCLUDED_BSLMF_REMOVECONST
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
//@PURPOSE: Provide a meta-function for removing top-level 'const'-qualifier.
//
//@CLASSES:
// bsl::remove_const: meta-function for removing top-level 'const'-qualifier
// bsl::remove_const_t: alias to the return type of the 'bsl::remove_const'
//
//@SEE_ALSO: bslmf_addconst
//
//@DESCRIPTION: This component defines a meta-function, 'bsl::remove_const' and
// declares an 'bsl::remove_const_t' alias to the return type of the
// 'bsl::remove_const', that may be used to remove any top-level
// 'const'-qualifier from a type.
//
// 'bsl::remove_const' and 'bsl::remove_const_t' meet the requirements of the
// 'remove_const' template defined in the C++11 standard [meta.trans.cv].
//
///Usage
///-----
// In this section we show intended use of this component.
//
///Example 1: Removing the 'const'-Qualifier of a Type
///- - - - - - - - - - - - - - - - - - - - - - - - - -
// Suppose that we want to remove any top-level 'const'-qualifier from a
// particular type.
//
// First, we create two 'typedef's -- a 'const'-qualified type ('MyConstType')
// and the same type without the 'const'-qualifier ('MyType'):
//..
// typedef int MyType;
// typedef const int MyConstType;
//..
// Now, we remove the 'const'-qualifier from 'MyConstType' using
// 'bsl::remove_const' and verify that the resulting type is the same as
// 'MyType':
//..
// assert(true ==
// (bsl::is_same<bsl::remove_const<MyConstType>::type, MyType>::value));
//..
// Finally, if the current compiler supports alias templates C++11 feature, we
// remove a 'const'-qualifier from 'MyConstType' using 'bsl::remove_const_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_const_t<MyConstType>, MyType>::value));
//#endif
//..
// Note, that the 'bsl::remove_const_t' avoids the '::type' suffix and
// 'typename' prefix when we want to use the result of the 'bsl::remove_const'
// meta-function in templates.
#include <bslscm_version.h>
#include <bsls_compilerfeatures.h>
#include <bsls_platform.h>
#include <stddef.h>
// Several compiler tool-chains have problems removing the const qualifiers
// from arrays. Additional documentation is below (where these macros are
// used).
#if defined(BSLS_PLATFORM_CMP_IBM)
# define BSLS_REMOVECONST_WORKAROUND_CONST_MULTIDIMENSIONAL_ARRAY 1
// The IBM xlC compiler has an odd issue trying to remove 'const'
// qualifiers from multidimensional arrays. This workaround was last
// verified as required for the xlC 12.1 compiler - more recent compilers
// still need testing.
#elif (defined(BSLS_PLATFORM_CMP_SUN) && BSLS_PLATFORM_CMP_VERSION < 0x5130) \
|| (defined(BSLS_PLATFORM_CMP_MSVC) \
&& BSLS_PLATFORM_CMP_VERSION <= 1900 \
&& _MSC_FULL_VER < 190023918)
# define BSLS_REMOVECONST_WORKAROUND_CONST_ARRAY 1
// The Microsoft compiler does not recognize array-types as cv-qualified
// when the element type is cv-qualified when performing matching for
// partial template specialization, but does get the correct result when
// performing overload resolution for functions (taking arrays by
// reference). Given the function dispatch behavior being correct, we
// choose to work around this compiler bug, rather than try to report
// compiler behavior, as the compiler itself is inconsistent depending on
// how the trait might be used. This also corresponds to how Microsoft
// itself implements the trait in VC2010 and later. Note that Microsoft
// fixed this bug in Update 2 for MSVC2015, which requires checking the
// '_MSC_FULL_VER' macro; the workaround below would be ambiguous when
// trying to remove 'const' from an array of 'const' elements with a
// conforming compiler.
#endif
namespace bsl {
// ===================
// struct remove_const
// ===================
template <class t_TYPE>
struct remove_const {
// This 'struct' template implements the 'remove_const' meta-function
// defined in the C++11 standard [meta.trans.cv], providing an alias,
// 'type', that returns the result. 'type' has the same type as the
// (template parameter) 't_TYPE' except that any top-level
// 'const'-qualifier has been removed. Note that this generic default
// template provides a 'type' that is an alias to 't_TYPE' for when
// 't_TYPE' is not 'const'-qualified. A template specialization is
// provided (below) that removes the 'const'-qualifier for when 't_TYPE' is
// 'const'-qualified.
// PUBLIC TYPES
typedef t_TYPE type;
// This 'typedef' is an alias to the (template parameter) 't_TYPE'.
};
// =================================
// struct remove_const<t_TYPE const>
// =================================
template <class t_TYPE>
struct remove_const<t_TYPE const> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is 'const'-qualified, provides a
// 'typedef', 'type', that has the 'const'-qualifier removed.
// PUBLIC TYPES
typedef t_TYPE type;
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE' except with the 'const'-qualifier removed.
};
#if defined(BSLS_REMOVECONST_WORKAROUND_CONST_MULTIDIMENSIONAL_ARRAY)
template <class t_TYPE, size_t N>
struct remove_const<t_TYPE[N]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On IBM compilers, it is
// necessary to separately 'remove_const' on the element type, and then
// reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<t_TYPE>::type type[N];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[N]' except with the 'const'-qualifier removed.
};
template <class t_TYPE, size_t N>
struct remove_const<const t_TYPE[N]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On IBM compilers, it is
// necessary to separately 'remove_const' on the element type, and then
// reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<const t_TYPE>::type type[N];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[N]' except with the 'const'-qualifier removed.
};
template <class t_TYPE>
struct remove_const<t_TYPE[]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On IBM compilers, it is
// necessary to separately 'remove_const' on the element type, and then
// reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<t_TYPE>::type type[];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[]' except with the 'const'-qualifier removed.
};
template <class t_TYPE>
struct remove_const<const t_TYPE[]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On IBM compilers, it is
// necessary to separately 'remove_const' on the element type, and then
// reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<const t_TYPE>::type type[];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[]' except with the 'const'-qualifier removed.
};
#elif defined(BSLS_REMOVECONST_WORKAROUND_CONST_ARRAY)
template <class t_TYPE>
struct remove_const<t_TYPE[]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On Microsoft compilers,
// it is necessary to separately 'remove_const' on the element type, and
// then reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<t_TYPE>::type type[];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[]' except with the 'const'-qualifier removed.
};
template <class t_TYPE, size_t LENGTH>
struct remove_const<t_TYPE[LENGTH]> {
// This partial specialization of 'bsl::remove_const', for when the
// (template parameter) 't_TYPE' is an array type. On Microsoft compilers,
// it is necessary to separately 'remove_const' on the element type, and
// then reconstruct the array dimensions.
// PUBLIC TYPES
typedef typename remove_const<t_TYPE>::type type[LENGTH];
// This 'typedef' is an alias to the same type as the (template
// parameter) 't_TYPE[N]' except with the 'const'-qualifier removed.
};
#endif
#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
// ALIASES
template <class t_TYPE>
using remove_const_t = typename remove_const<t_TYPE>::type;
// 'remove_const_t' is an alias to the return type of the
// 'bsl::remove_const' meta-function. Note, that the 'remove_const_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 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 ----------------------------------