loop on character

loop on character

[Bernd Specht]

Although I've worked with Ada for a few years, I've got a problem now that 
looks a bit like a beginners problem to me. Can someone help me?

I wrote a statement like this:

for c in '0'..'9'
loop
...
end loop;

and the compiler says "ambigous character literals (could be 
Wide_Character)"

what would be the correct way to write this?

Ok, I can declare some variables first, but I think there must be a better 
way.

low : Character := '0';
high : Character  := '9';

for c in low .. high
loop
...
end loop;

Re: loop on character

[Adam Beneschan]

On Oct 8, 2:26 pm, Bernd.Spe...@gmx.com (Bernd Specht) wrote:
> Although I've worked with Ada for a few years, I've got a problem now that
> looks a bit like a beginners problem to me. Can someone help me?
>
> I wrote a statement like this:
>
> for c in '0'..'9'
> loop
> ...
> end loop;
>
> and the compiler says "ambigous character literals (could be
> Wide_Character)"
>
> what would be the correct way to write this?

for C in Character range '0' .. '9' loop

                             -- Adam

Re: loop on character

[Jeffrey R. Carter]

Adam Beneschan wrote:
> 
> for C in Character range '0' .. '9' loop

You can also do

for C in Character'('0') .. '9' loop

which gives an interesting, if difficult to read, sequence of 3 apostrophes 
separated by other characters.

As long as the compiler knows the type of at least one of the literals it will 
be happy. As the OP pointed out, making at least one of them an object will do 
it. If he wants the literals in the loop statement, "Character range" would be 
my choice.

-- 
Jeff Carter
"Hello! Smelly English K...niggets."
Monty Python & the Holy Grail
08

Re: loop on character

[Jerry]

On Oct 8, 2:42 pm, Adam Beneschan <a...@irvine.com> wrote:
>
> for C in Character range '0' .. '9' loop
>
>                              -- Adam

Does this construction have a name? By "this construction" I mean the
presence of Character in the for statement. Presumably other types can
be included at that position.

The Perpetual Newb,
Jerry

Re: loop on character

[Adam Beneschan]

On Oct 9, 12:13 pm, Jerry <lancebo...@qwest.net> wrote:
> On Oct 8, 2:42 pm, Adam Beneschan <a...@irvine.com> wrote:
>
>
>
> > for C in Character range '0' .. '9' loop
>
> >                              -- Adam
>
> Does this construction have a name? By "this construction" I mean the
> presence of Character in the for statement.

It doesn't quite have a name of its own.  "Character range '0'..'9'"
is a discrete_subtype_definition, but it would still be that without
the type name.  Going further, this form of
discrete_subtype_definition is a discrete_subtype_indication, which is
just a kind of subtype_indication, which is a type or subtype name
optionally followed by a constraint.  See 5.5(4), 3.6(6), 3.2.2(3).
Note the *optionally*: you can write a loop providing just a type
(subtype) name without the range constraint---see Bob's response for
an example.

> Presumably other types can
> be included at that position.

Yes, but only discrete types (integer or enumeration).

                                -- Adam

Re: loop on character

[Robert A Duff]

Bernd.Specht@gmx.com (Bernd Specht) writes:

> low : Character := '0';
> high : Character  := '9';
>
> for c in low .. high
> loop
> ...
> end loop;

If you do it that way, low and high should be constant.

Others have suggested "for C in Character...",
which is probably what you want.

Here's another variation:

subtype Digit is Character range '0'..'9';
for C in Digit loop...

- Bob