Question

Say that I have some user-defined complex struct, like

struct usrStruct{
     double a;
     T1 b;
     T2 c;
     /* and so on...*/
}

which is used as a basic element for a std::vector, std::list or anything iterable..

Say that the std::vector<usrStruct> is passed to a function of mine through iterators

  template<class InputIterator>  
  T myFoo( InputIterator first, InputIterator last ){ /*...*/ }.

Q: Is there a standard way to override operator*() of the InputIterator, (in this case of std::vector<usrStruct>::iterator ) so that myFoo just interacts with the member a?

i.e., so that

  *first == (*first).a;

and thus myFoo works orthogonally with respect to the whole definition of usrStruct?

Thank you.

Answer 1

No, you cannot do that. You can make your struct implicitly convertible to a double (via operator double). Or you can allow direct comparisons by overloading operator==(usrSruct,double) and/or operator==(double,usrStruct).