about unary_function

[LinLMa]

Hello everyone,
I am wondering what is the practical usage of unary_function? Could
anyone list some practical benefits?

My question is, a class like

class Foo : public std::unary_function<class A, class B>

is always the same (could use similar implementation) to

template <class A, class Bclass Foo

So we could always use the alternative approach to replace
unary_function.
thanks in advance,
George

[Pete Becker]

On 2007-12-01 04:59:58 -0500, Li****@gmail.com said:

>
I am wondering what is the practical usage of unary_function? Could
anyone list some practical benefits?

std::unary_function provides two typedef nams that can be used by other
classes to determine the argument type and the result type of a class's
function call operator. For example, the standard library templates
std::negate and std::unary_negate use this information to determine the
argument type and return type of their own function call operators.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)