text: // 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 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) '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 'TYPE' for when 'TYPE' is not
      // 'const'-qualified.  A template specialization is provided (below) that
      // removes the 'const'-qualifier for when 'TYPE' is 'const'-qualified.
  
      // PUBLIC TYPES
      typedef TYPE type;
          // This 'typedef' is an alias to the (template parameter) 'TYPE'.
  };
  
                           // ===============================
                           // struct remove_const<TYPE const>
                           // ===============================
  
  template <class TYPE>
  struct remove_const<TYPE const> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) 'TYPE' is 'const'-qualified, provides a 'typedef',
       // 'type', that has the 'const'-qualifier removed.
  
      // PUBLIC TYPES
      typedef TYPE type;
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE' except with the 'const'-qualifier removed.
  };
  
  #if defined(BSLS_REMOVECONST_WORKAROUND_CONST_MULTIDIMENSIONAL_ARRAY)
  template <class TYPE, size_t N>
  struct remove_const<TYPE[N]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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<TYPE>::type type[N];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[N]' except with the 'const'-qualifier removed.
  };
  
  template <class TYPE, size_t N>
  struct remove_const<const TYPE[N]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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 TYPE>::type type[N];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[N]' except with the 'const'-qualifier removed.
  };
  
  template <class TYPE>
  struct remove_const<TYPE[]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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<TYPE>::type type[];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[]' except with the 'const'-qualifier removed.
  };
  
  template <class TYPE>
  struct remove_const<const TYPE[]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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 TYPE>::type type[];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[]' except with the 'const'-qualifier removed.
  };
  #elif defined(BSLS_REMOVECONST_WORKAROUND_CONST_ARRAY)
  template <class TYPE>
  struct remove_const<TYPE[]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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<TYPE>::type type[];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[]' except with the 'const'-qualifier removed.
  };
  
  template <class TYPE, size_t LENGTH>
  struct remove_const<TYPE[LENGTH]> {
       // This partial specialization of 'bsl::remove_const', for when the
       // (template parameter) '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<TYPE>::type type[LENGTH];
          // This 'typedef' is an alias to the same type as the (template
          // parameter) 'TYPE[N]' except with the 'const'-qualifier removed.
  };
  #endif
  
  #ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
  
  // ALIASES
  template <class TYPE>
  using remove_const_t = typename remove_const<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 ----------------------------------
  