Component bslmf_ispointer [Package bslmf]

Provide a compile-time check for pointer types. More...

Classes
struct	bsl::is_pointer< t_TYPE >
struct	bsl::is_pointer< t_TYPE * >
struct	bsl::is_pointer< t_TYPE *const >
struct	bsl::is_pointer< t_TYPE *volatile >
struct	bsl::is_pointer< t_TYPE *const volatile >

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Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Verify Pointer Types

Purpose:

Provide a compile-time check for pointer types.

Classes:

bsl::is_pointer	standard meta-function for determining pointer types
bsl::is_pointer_v	the result value of the bsl::is_pointer meta-function
bsl::IsPointer	meta-function for determining pointer types

See also:

Component bslmf_integralconstant

Description:

This component defines two meta-functions, bsl::is_pointer and BloombergLP::bslmf::IsPointer and a template variable bsl::is_pointer_v, that represents the result value of the bsl::is_pointer meta-function. All these meta-functions may be used to query whether or not a type is a pointer type.

bsl::is_pointer meets the requirements of the is_pointer template defined in the C++11 standard [meta.unary.cat], while bslmf::IsPointer was devised before is_pointer was standardized.

The two meta-functions are functionally equivalent. The major difference between them is that the result for bsl::is_pointer is indicated by the class member value, while the result for bslmf::IsPointer is indicated by the class member VALUE.

Note that bsl::is_pointer should be preferred over bslmf::IsPointer, and in general, should be used by new components.

Also note that the template variable is_pointer_v is defined in the C++17 standard as an inline variable. If the current compiler supports the inline variable C++17 compiler feature, bsl::is_pointer_v is defined as an inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_pointer_v is defined as a non-inline constexpr bool variable. See BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES and BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES macros in bsls_compilerfeatures component for details.

Usage:

In this section we show intended use of this component.

Example 1: Verify Pointer Types:

Suppose that we want to assert whether a particular type is a pointer type.

First, we create two typedefs -- a pointer type and a non-pointer type:

  typedef int  MyType;
  typedef int *MyPtrType;

Now, we instantiate the bsl::is_pointer template for each of the typedefs and assert the value static data member of each instantiation:

  assert(false == bsl::is_pointer<MyType>::value);
  assert(true  == bsl::is_pointer<MyPtrType>::value);

Note that if the current compiler supports the variable templates C++14 feature then we can re-write the snippet of code above using the bsl::is_pointer_v variable as follows:

#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
  assert(false == bsl::is_pointer_v<MyType>);
  assert(true  == bsl::is_pointer_v<MyPtrType>);
#endif