22 General utilities library [utilities]

22.10 Function objects [function.objects]

22.10.15 Function object binders [func.bind] Class template is_bind_expression [func.bind.isbind]

namespace std { template<class T> struct is_bind_expression; // see below }
The class template is_bind_expression can be used to detect function objects generated by bind.
The function template bind uses is_bind_expression to detect subexpressions.
Specializations of the is_bind_expression template shall meet the Cpp17UnaryTypeTrait requirements ([meta.rqmts]).
The implementation provides a definition that has a base characteristic of true_type if T is a type returned from bind, otherwise it has a base characteristic of false_type.
A program may specialize this template for a program-defined type T to have a base characteristic of true_type to indicate that T should be treated as a subexpression in a bind call.