It's not something that is done consistently, but we've often used the ()
operator for things that feel like a function, and consequently may be
replaced with functions or lambdas as we move more towards C++11. Keep in
mind that the vast majority of our C++ was written before we had any C++11
support whatsoever. :)
For example, if you want to filter a collection, you would want to pass a
functor predicate as opposed to a subclass of a Predicate type:
filtered = filter(ints, [](int i) { return i > 5; });
vs.
template <typename T>
class GreaterThanFive : public Predicate
{
bool apply(const T& t) { return t > 5; }
};
filtered = filter(ints, predicate);
Here the type system isn't really adding much value, what we really care
about is the *signature* of the predicate.
On Tue, Jan 27, 2015 at 1:56 AM, Alexander Rojas <[email protected]>
wrote:
> I was checking master.cpp, and I saw that a lot of the objects there are
> functors, which is OK unless you get a pointer to the functor instance and
> then call its operator() which looks something like
> (*instance)(parameters). I have always find this syntax somewhat confusing
> since it looks a lot like an old C cast.
>
> Is there a rationale for using this functor model everywhere?
>
> Isn’t it possible to use the operator as a wrapper for some method call,
> so when applied on a pointer we call the method directly? I find that much
> more readable.
