Component bslmf_isarray [Package bslmf]

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

Classes
struct	bsl::is_array< t_TYPE >
struct	bsl::is_array< t_TYPE[t_NUM_ELEMENTS]>
struct	bsl::is_array< t_TYPE[]>

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Detailed Description

Outline

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

Purpose:

Provide a compile-time check for array types.

Classes:

bsl::is_array	standard meta-function for detecting array types
bsl::is_array_v	the result value of the bsl::is_array meta-function
bslmf::IsArray	meta-function for detecting array types

Description:

This component defines two meta-functions, bsl::is_array and BloombergLP::bslmf::IsArray and a template variable bsl::is_array_v, that represents the result value of the bsl::is_array meta-function. All these meta-functions may be used to query whether a type is an array type.

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

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

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

Also note that the template variable is_array_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_array_v is defined as inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_array_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 Array Types:

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

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

  typedef int MyType;
  typedef int MyArrayType[]

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

  assert(false == bsl::is_array<MyType>::value);
  assert(true  == bsl::is_array<MyArrayType>::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_array_v variable as follows:

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