Syntax Trouble

[ToniAz]

Hello everyone!

I am having a bit trouble understanding what the following line does:

virtual int operator()(Key & k) = 0;

where this declaration comes as a public member of a hash function class.

[Bazzy]

It's a pure virtual function, see http://www.cplusplus.com/doc/tutorial/polymorphism/

[ToniAz]

Aah, pure virtual function, abstract base classes, okay...

[Zhuge]

That's just how you declare a virtual function. It has to do with setting the vtable function pointer to null, I believe.

[rocketboy9000]

This is one of the most bizarre things in c++, but it's the best they can do, because c++ has a huge amount of grammar.

[sohguanh]

Besides being a pure virtual function, it is also a function call operator overload.