Exceptions and functions. Second round?

[Jerzy Karczmarczuk]

Tony Finch cites Hans Aberg, who comments the posting of Eric Zuurbier
who writes that: "... Exceptions are merely a way to structure the code, 
so that the main line and error handling can be neatly separated."


* > This is the original idea, but I pointed out that exceptions are in
* > fact much deeper: They can be used as a programming technique too,
* > and further, many common language constructs (such as "return",
* > "break", etc in C++) can be viewed as special cases of exception
* > handling.      [HA]

> 
> Indeed, in Modula-3, RETURN and EXIT are defined in terms of
> exceptions.
> 
> I like the idea of the non-deterministic exception system that has
> been proposed, but it'll be interesting to see how well it works in
> real life...
> 
> Tony.
 

I am afraid that we are repeating what has been already said, but OK,
this is the essence of wisdom...

I don't think that I would agree with such philosophy. "break" in C is
nothing more than a structured "goto". Break from "switch" is just
a jump, from a loop it might do some cleanup (if the loop index is
stacked). "Return" is also a jump with the cleanup of the last instance
frame.


As we all know, all this can be represented by continuations, and this
is a practical issue, not a statement that "all Turing machines are
equal, only some are more equal than the others..."

There is - in my opinion - nothing "exceptional" in *standard* imperative
control structures. OK, I admit that I am a sinner myself, and I had
written some small event-driven programs using (ppardonnez le mot)
"longjump" in C, but I believe strongly that the functional programming
community with the monadic religion etc. is much more close to the Truth.

Jerzy Karczmarczuk
Caen, France