C++ named requirements: BooleanTestable

Specifies that an expression of such a type and value category is convertible to bool, and for which the logical operators for the type or two different BooleanTestable types have the usual behavior (including short-circuiting).

# Notes

The standard does not define a named requirement with this name. It was originally proposed in an early resolution of LWG2114, but was superseded by the exposition-only concept boolean-testable in the final resolution P2167R3. Because implementations generally expect the provided types to model boolean-testable even in pre-C++20 modes, we intentedly treat P2167R3 as a defect report and transform the boolean-testable to legacy named requirements.

When the && and || operators are used with operands whose type and value category are BooleanTestable, built-in versions are selected and short-circuit evaluation is performed.

The type and value category of an expression e meet the BooleanTestable requirements if and only if decltype((e)) models boolean-testable.

Examples of BooleanTestable types (with any value category) include bool, std::true_type(since C++11), std::bitset::reference, and int*.

# Defect reports

# See also

• boolean-testable