33 Execution control library [exec]

33.2 Queries and queryables [exec.queryable]

33.2.2 queryable concept [exec.queryable.concept]

namespace std { template<class T> concept queryable = destructible<T>; // exposition only }

The exposition-only queryable concept specifies the constraints on the types of queryable objects.

Let env be an object of type Env.

The type Env models queryable if for each callable object q and a pack of subexpressions args, if requires { q(env, args...) } is true then q(env, args...) meets any semantic requirements imposed by q.