Dynamic dispatching reloaded

In previous posts I was exploring a feature I am interested in, and which I have called in many different ways — here I will call it dynamic dispatching.

The previous articles:

Conclusion of those posts: out of the box only Perl6 has it.

The story went on like this: I stirred the net for a solution in C++. And I obtained it.


Nested functions

Some languages allow nested functions (or procedures, or subroutines, or whatever you prefer to call them), others don't.

I think those can be useful and I wonder why they aren't embraced by all living programming languages.


Changing input validation in an established API

Let's suppose that your server S exposes an API and that this API is used by many clients, or maybe just one — it doesn't really matter.

Let's focus on a client only, let's call it C. Documents were exchanged between S and C, so to agree on the interface.

After that, tests were done and none raised issues or, if they did, they were fixed.

The tests stated that S and C can talk, that they can understand each other, that C calls S correctly, that S acts properly according to the request, that C parses server's answer correctly, and so on.

Everything works fine, or mostly fine, since the beginning.