Why have unary_function, binary_function been removed from C++11?

Question

I found that binary_function is removed from C++11. I am wondering why.

C++98:

template  struct less : binary_function &l         


        

Answer 1

With variadic templates, a lot of general function composing can be expressed much more simply and consistently, so all of the old cruft is no longer necessary:

Do use:

• std::function
• std::bind
• std::mem_fn
• std::result_of
• lambdas

Don't use:

• std::unary_function, std::binary_function
• std::mem_fun
• std::bind1st, std::bind2nd