bslmf_isenum

Macros
#define	bslmf_IsEnum   bslmf::IsEnum
	This alias is defined for backward compatibility.

Detailed Description

Outline

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

Purpose

Provide compile-time check for determining enumerated types.

Classes

• bsl::is_enum: standard meta-function for determining enumerated types
• bsl::is_enum_v: the result value of the bsl::is_enum meta-function
• bslmf::IsEnum: meta-function for determining enumerated types

See also

bslmf_isfundamental

Description

This component defines two meta-functions, bsl::is_enum and BloombergLP::bslmf::IsEnum and a template variable bsl::is_enum_v, that represents the result value of the bsl::is_enum meta-function. All these meta-functions may be used to query whether a type is an enumerated type, optionally qualified with const or volatile.

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

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

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

Also note that the template variable is_enum_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_enum_v is defined as an inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_enum_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 Enumerated Types

Suppose that we want to assert whether a set of types are enum types.

First, we create an enumerated type, MyEnum, and a class type, MyClass:

enum MyEnum { MY_ENUMERATOR = 5 };
class MyClass { explicit MyClass(MyEnum); };

Now, we instantiate the bsl::is_enum template for both types we defined previously, and assert the value static data member of each instantiation:

assert(true  == bsl::is_enum<MyEnum>::value);
assert(false == bsl::is_enum<MyClass>::value);

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

#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
  assert(true  == bsl::is_enum_v<MyEnum>);
  assert(false == bsl::is_enum_v<MyClass>);
#endif

Macro Definition Documentation

bslmf_IsEnum

#define bslmf_IsEnum   bslmf::IsEnum