5.10. Binding

We could stop here. By now, we have everything in place—Functor supports all the C++ callable entities defined in the beginning of the discussion, and in a nice manner. However, as Pygmalion might have remarked, sometimes the actual outcome of work is impossible to predict when you start doing it.

As soon as Functor is ready, new ideas come to mind. For instance, we'd like to be able to convert from a type of Functor to another. One such conversion is binding: Given a Functor that takes two integers, you want to bind one integer to some fixed value and let only the other one vary. Binding yields a Functor that takes only one integer, because the other one is fixed and therefore known, as illustrated in the following example.