Re: else ladders practice

On 05/11/2024 20:33, David Brown wrote:

On 05/11/2024 20:39, Waldek Hebisch wrote:

David Brown <david.brown@hesbynett.no> wrote:

On 05/11/2024 13:42, Waldek Hebisch wrote:

Bart <bc@freeuk.com> wrote:

>
Then we disagree on what 'multi-way' select might mean. I think it means
branching, even if notionally, on one-of-N possible code paths.

>
OK.

>
I appreciate this is what Bart means by that phrase, but I don't agree
with it.  I'm not sure if that is covered by "OK" or not!

>
You may prefer your own definition, but Bart's is resonable one.

 The only argument I can make here is that I have not seen "multi-way select" as a defined phrase with a particular established meaning.

Well, it started off as 2-way select, meaning constructs like this:
    x = c ? a : b;
    x := (c | a | b)
Where one of two branches is evaluated. I extended the latter to N-way select:
    x := (n | a, b, c, ... | z)
Where again one of these elements is evaluated, selected by n (here having the values of 1, 2, 3, ... compared with true, false above, but there need to be at least 2 elements inside |...| to distinguish them).
I applied it also to other statements that can be provide values, such as if-elsif chains and switch, but there the selection might be different (eg. a series of tests are done sequentially until a true one).
I don't know how it got turned into 'multi-way'.
Notice that each starts with an assignment (or the value is used in other ways like passing to a function), so provision has to be made for some value always to be returned.
Such N-way selections can be emulated, for example:
    if (c)
      x = a;
    else
      x = b;
But because the assignment has been brought inside (a dedicated one for each branch), the issue of a default path doesn't arise. You can leave out the 'else' for example; x is just left unchanged.
This doesn't work however when the result is passed to a function:
     f(if (c) a);
what is passed when c is false?