Assume the loop:

for t of C loop
if f(t) then
do something....
elsif f(t) > f1 then
exit;
end if;
end loop;

I would like to simplify this construct (somehow) like this:

for t of C when f(t) loop
do something....
end loop;

However, this is not computationally effective, since t in this case runs through the whole C.
Any ideas for a compromise?

reinert

mandag 23. oktober 2023 kl. 07:03:01 UTC+2 skrev reinert:
> Assume the loop:
>
> for t of C loop
> if f(t) then
> do something....
> elsif f(t) > f1 then
> exit;
> end if;
> end loop;
>
> I would like to simplify this construct (somehow) like this:
>
> for t of C when f(t) loop
> do something....
> end loop;
>
> However, this is not computationally effective, since t in this case runs through the whole C.
> Any ideas for a compromise?
>
> reinert
Just a correction of the subject, it should be: How to exit from "for t *of* C when f(t) loop ? -reinert

On Monday, October 23, 2023 at 6:04:30 PM UTC+11, reinert wrote:
> mandag 23. oktober 2023 kl. 07:03:01 UTC+2 skrev reinert:
> > Assume the loop:
> >
> > for t of C loop
> > if f(t) then
> > do something....
> > elsif f(t) > f1 then
> > exit;
> > end if;
> > end loop;
> >
> > I would like to simplify this construct (somehow) like this:
> >
> > for t of C when f(t) loop
> > do something....
> > end loop;
> >
> > However, this is not computationally effective, since t in this case runs through the whole C.
> > Any ideas for a compromise?
> >
> > reinert
> Just a correction of the subject, it should be: How to exit from "for t *of* C when f(t) loop ? -reinert
Normally one does something
t := C'first;
loop
do something...
exit when Condition;
t := t + 1;
end loop;

The conditon is just a boolean expression. It can be as simple or as complicated as one desires.

I would like an exit possibility somehow like this:

for t of C when f(t), but exit when f(t) loop
do something....
end loop;

Three lines less - keeping errors down :-)

reinert

onsdag 25. oktober 2023 kl. 04:32:58 UTC+2 skrev min...@gmail.com:
> On Monday, October 23, 2023 at 6:04:30 PM UTC+11, reinert wrote:
> > mandag 23. oktober 2023 kl. 07:03:01 UTC+2 skrev reinert:
> > > Assume the loop:
> > >
> > > for t of C loop
> > > if f(t) then
> > > do something....
> > > elsif f(t) > f1 then
> > > exit;
> > > end if;
> > > end loop;
> > >
> > > I would like to simplify this construct (somehow) like this:
> > >
> > > for t of C when f(t) loop
> > > do something....
> > > end loop;
> > >
> > > However, this is not computationally effective, since t in this case runs through the whole C.
> > > Any ideas for a compromise?
> > >
> > > reinert
> > Just a correction of the subject, it should be: How to exit from "for t *of* C when f(t) loop ? -reinert
> Normally one does something
> t := C'first;
> loop
> do something...
> exit when Condition;
> t := t + 1;
> end loop;
>
> The conditon is just a boolean expression. It can be as simple or as complicated as one desires.

On Friday, October 27, 2023 at 10:53:15 AM UTC-4, reinert wrote:
> I would like an exit possibility somehow like this:
>
> for t of C when f(t), but exit when f(t) loop
> do something....
> end loop;
>
> Three lines less - keeping errors down :-)
>
> reinert
> onsdag 25. oktober 2023 kl. 04:32:58 UTC+2 skrev :
> > On Monday, October 23, 2023 at 6:04:30 PM UTC+11, reinert wrote:
> > > mandag 23. oktober 2023 kl. 07:03:01 UTC+2 skrev reinert:
> > > > Assume the loop:
> > > >
> > > > for t of C loop
> > > > if f(t) then
> > > > do something....
> > > > elsif f(t) > f1 then
> > > > exit;
> > > > end if;
> > > > end loop;
> > > >
> > > > I would like to simplify this construct (somehow) like this:
> > > >
> > > > for t of C when f(t) loop
> > > > do something....
> > > > end loop;
> > > >
> > > > However, this is not computationally effective, since t in this case runs through the whole C.
> > > > Any ideas for a compromise?
> > > >
> > > > reinert
> > > Just a correction of the subject, it should be: How to exit from "for t *of* C when f(t) loop ? -reinert
> > Normally one does something
> > t := C'first;
> > loop
> > do something...
> > exit when Condition;
> > t := t + 1;
> > end loop;
> >
> > The conditon is just a boolean expression. It can be as simple or as complicated as one desires.

Would the new Ada22 feature of iterator filters help at all?
http://www.ada-auth.org/standards/22over/html/Ov22-4-6.html

reinert schrieb am Freitag, 27. Oktober 2023 um 16:53:15 UTC+2:
> I would like an exit possibility somehow like this:
>
> for t of C when f(t), but exit when f(t)
except when Y then skip next -- many more lines saved ;-)
> loop
> do something....
> end loop;
>
> Three lines less - keeping errors down :-)

On Saturday, October 28, 2023 at 7:42:10 AM UTC-7, AdaMagica wrote:
> reinert schrieb am Freitag, 27. Oktober 2023 um 16:53:15 UTC+2:
> > I would like an exit possibility somehow like this:
> >
> > for t of C when f(t), but exit when f(t)
> except when Y then skip next -- many more lines saved ;-)
> > loop
> > do something....
> > end loop;
> >
'exit when condition;' is perfectly legal Ada.

It is more problematic that you are executing f(t) twice; that's either wrong if it has side effects, or wasteful if not.
And you are treating f(t) as returning a Boolean and a scalar!

for t of C loop
declare
A : foo renames f(t);
begin
exit when A; -- Boolean
exit when A >= f1; -- scalar
do something;
end;
end loop;