20 General utilities library [utilities]

20.9 Function objects [function.objects]

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

namespace std {
  template<class T> struct is_bind_expression; // see below

is_bind_expression can be used to detect function objects generated by bind. bind uses is_bind_expression to detect subexpressions.

Instantiations of the is_bind_expression template shall meet the UnaryTypeTrait requirements ([meta.rqmts]). The implementation shall provide a definition that has a BaseCharacteristic of true_type if T is a type returned from bind, otherwise it shall have a BaseCharacteristic of false_type. A program may specialize this template for a user-defined type T to have a BaseCharacteristic of true_type to indicate that T should be treated as a subexpression in a bind call.