411 REFERENCE · Wikibooks
C++ Language/Templates/Traits/UnaryPredicateTraits
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A "predicate trait" is a boolean value based on some characteristic of a type.
C++ provides many built-in "dummy templates" for a variety of these characteristics (e.g., std::is_floating_point<int>::value resolves to false at compile-time).
Additional information about unary predicate traits (includes interactive examples)