Re: Loops (was Re: do { quit; } else { })

On 17/04/2025 12:16, bart wrote:

On 17/04/2025 03:18, Keith Thompson wrote:

If you want to implement, say, an Ada-style for loop, detecting
overflow is not an issue at the language level.  The issue is that
for the following (I think the Ada syntax is clear enough):
>
     for I in Integer'Last-1 .. Integer'Last loop
         // whatever
     end loop;
>
the language semantics specify that the body of the loop must be
executed with I equal to Integer'Last-1, and then with I equal to
Integer'Last.  It's the compiler's job to figure out how to do that,
either without triggering an overflow or by handling it cleanly enough
that it doesn't change the behavior.

 Does it define what value I has when the loop terminates, or is the scope of I local to the loop body?

My experiments show that:
(1) Loop variables only have scope within the loop
(2) Loop variables are read-only; they cannot be modified by user code
This makes it much simpler to get the desired behaviour of a loop index iterating up to the maximum value of the type.
So a comparison with other languages (either C or mine) is not that fair.
Mine can be more restrictive, and I can make it more so (eg. restrict the scope of loop variables), but I have no interest in reimplementing Ada.