7.11 C++ Concepts

C++ concepts provide much-improved support for generic programming. In particular, they allow the specification of constraints on template arguments. The constraints are used to extend the usual overloading and partial specialization capabilities of the language, allowing generic data structures and algorithms to be “refined” based on their properties rather than their type names.

The following keywords are reserved for concepts.

assumes

States an expression as an assumption, and if possible, verifies that the assumption is valid. For example, assume(n > 0).

axiom

Introduces an axiom definition. Axioms introduce requirements on values.

forall

Introduces a universally quantified object in an axiom. For example, forall (int n) n + 0 == n).

concept

Introduces a concept definition. Concepts are sets of syntactic and semantic requirements on types and their values.

requires

Introduces constraints on template arguments or requirements for a member function of a class template.

The front end also exposes a number of internal mechanism that can be used to simplify the writing of type traits. Note that some of these traits are likely to be removed in the future.

__is_same (type1, type2)

A binary type trait: true whenever the type arguments are the same.