Provide a meta-function for adding top-level cv-qualifiers.
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Detailed Description
- Outline
-
-
- 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:
- Component 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
: 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.