conditional

Applicability

Product	Supported
Atlas A3 training products/Atlas A3 inference products	√
Atlas A2 training products/Atlas A2 inference products	√
Atlas 200I/500 A2 inference products	x
Atlas inference product's AI Core	x
Atlas inference product's Vector Core	x
Atlas training products	x

Function

Selects a type from two types based on a Boolean condition during program building as a type characteristics tool defined in the <type_traits> header file. This API can be used in template metaprogramming to select a proper type based on different conditions, enhancing the universality and flexibility of code.

conditional has a nested type member whose value depends on the value of Bp. If Bp is set to true, the value of conditional<Bp, If, Then>::type is If. If Bp is set to false, the value of conditional<Bp, If, Then>::type is Then.

Prototype

template <bool Bp, typename If, typename Then>
struct conditional;

Parameters

**Table 1** Template parameters
Parameter	Description
Bp	A Boolean constant expression, which is used as the condition for selecting a type.
If	Type selected when Bp is set to true.
Then	Type selected when Bp is set to false.

Restrictions

None

Returns

The static constant member type of conditional is used to obtain the return value. The values of conditional<Bp, If, Then>::type are as follows:

If: Bp is set to true.
Then: Bp is set to false.

Example

// Define two different types.
struct TypeA {
    __aicore__ inline static void print() {
        AscendC::PRINTF("This is TypeA..\n");
    }
};

struct TypeB {
    __aicore__ inline static void print() {
        AscendC::PRINTF("This is TypeB..\n");
    }
};

// Select a type based on conditions.
template <bool Condition>
__aicore__ inline void selectType() {
    using SelectedType = typename AscendC::Std::conditional<Condition, TypeA, TypeB>::type;
    SelectedType::print();
}

// Define a template function to select different types based on conditions.
template <bool Condition>
__aicore__ inline void selectOtherType() {
    using SelectedType = typename std::conditional<Condition, int, float>::type;
    if constexpr (std::is_same_v<SelectedType, int>) {
        AscendC::PRINTF("Selected type is int.\n");
    } else {
        AscendC::PRINTF("Selected type is float.\n");
    }
}

// If the condition is true, select TypeA.
selectType<true>();
// If the condition is false, select TypeB.
selectType<false>();

// Test when the condition is true.
selectOtherType<true>();
// Test when the condition is false.
selectOtherType<false>();

// Execution result:
This is TypeA..
This is TypeB..
Selected type is int.
Selected type is float.

Parent topic: Type Traits