Re: character literals

[Robert A Duff <bobduff@shell01.TheWorld.com>]

adambeneschan@gmail.com writes:

> On Tuesday, February 11, 2014 2:27:57 PM UTC-8, ag...@drrob1.com wrote:
>> I have been having a difficulty in my code with character literals.
>> 
>> For example
>> 
>>  IF ch in '0' .. '9' THEN

Note to OP:  If you have questions about an error message, it's best to
cut&paste the exact complete compilable code that caused the error,
along with the exact text of the error message.

The above is legal given the right declaration of ch, but you
didn't show that; there are all sorts of reasons the above could
be illegal.

Also look at Ada.Characters.Handling.  You can call the Is_Digit function.

> Finally, the language does have one special rule:
>
>     for I in 0 .. 9 loop
>
> The literals 0 and 9 could be resolved to any integer type, which
> would make this ambiguous since there are normally multiple integer
> types visible in the program (Integer, Long_Integer, Short_Integer,
> maybe types in Interfaces if you "use" that packaged).  But the
> language rules decree that the type will be Integer in that case.
> This is a situation where some programmers might recommend making the
> type Integer explicit.

Like me.  I think the special-case for Integer is a kludge, so I
would write:

    for I in Some_Type range 0 .. 9 loop

One exception:  If I want to say "do this 5 times", I might write:

    for I in 1 .. 5 loop

and there are no references to I in the loop, so its type is irrelevant.

On the other hand, if the type is clear from the bounds, as in

    for I in 1 .. Some_Array'Last - 1 loop

I wouldn't put the type in.

- Bob