Component bslmf_ismemberfunctionpointer [Package bslmf]

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

Classes
struct	bsl::is_member_function_pointer< t_TYPE >
struct	bsl::is_member_function_pointer< t_TYPE t_CLASS::* >
struct	bsl::is_member_function_pointer< t_TYPE t_CLASS::*const >
struct	bsl::is_member_function_pointer< t_TYPE t_CLASS::*volatile >
struct	bsl::is_member_function_pointer< t_TYPE t_CLASS::*const volatile >

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Detailed Description

Outline

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

Purpose:

Provide a compile-time check for member function pointer types.

Classes:

bsl::is_member_function_pointer	standard meta-function
bsl::is_member_function_pointer_v	the result value of the meta-function

See also:

Component bslmf_memberfunctionpointertraits, Component bslmf_ismemberobjectpointer

Description:

This component defines a meta-function, bsl::is_member_function_pointer and a template variable bsl::is_member_function_pointer_v, that represents the result value of the bsl::is_member_function_pointer meta-function, that may be used to query whether a type is a pointer to non-static member function type.

bsl::is_member_function_pointer meets the requirements of the is_member_function_pointer template defined in the C++11 standard [meta.unary.cat].

Note that, in order to support the widest range of compilers, this component depends on bslmf_memberfunctionpointertraits, which does not support member functions with C-style (varargs) elipses. Thus, bsl::is_member_function_pointer will return a false negative if invoked on a pointer to such a member.

Note that the template variable is_member_function_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_member_function_pointer_v is defined as an inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_member_function_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 Member Function Pointer Types:

Suppose that we want to assert whether a set of types are pointers to non-static member function types.

First, we create a user-defined type MyStruct:

  struct MyStruct
  {
  };

Now, we create two typedefs -- a function pointer type and a member function pointer type:

  typedef int (MyStruct::*MyStructMethodPtr) ();
  typedef int (*MyFunctionPtr) ();

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

  assert(false == bsl::is_member_function_pointer<MyFunctionPtr    >::value);
  assert(true  == bsl::is_member_function_pointer<MyStructMethodPtr>::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_member_function_pointer_v variable as follows:

#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
  assert(false == bsl::is_member_function_pointer_v<MyFunctionPtr    >);
  assert(true  == bsl::is_member_function_pointer_v<MyStructMethodPtr>);
#endif