What are functors?
Quoting from this website: “Functors are functions with a state.
In C++ you can realize them as a class with one or more private members to store the state and with an
operator() to execute the function. “
A typical use of a functor (function object) is in writing callback functions. And that is also my usage when using Boost Graph Library.
I tried to used:
template function in the graph library, and the
predicate parameter is a functor object, see here.
Therefore I had to make a functor class before using such a function.
To make a functor class in C++, you simply create an ordinary
class (or a
struct) that overloads
operator(). To see
some concrete examples, check out this wikipedia post. To
achieve something similar in C, you then make use of function pointers and pass them as parameters.