Re: Peculiarities of "of" syntax

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 1/11/20 7:05 PM, Alejandro R. Mosteo wrote:
> 
> procedure Pro is
>     type Int_Array is array (Positive range <>) of Integer;
>     Arr : Int_Array := (others => 0);
> begin
> 
>     -- 1)
>     for Z of Arr loop -- of course valid
>        null;
>     end loop;
> 
>     -- 2)
>     for Z of Int_Array'(Arr & Arr) loop -- also works
>        null;
>     end loop;
> 
>     -- INVALID
> 
>     -- 3)
>     for Z of Arr & Arr loop
>       --  Error is "missing loop"
>       null;
>     end loop;
> 
>     -- 4)
>     for Z of (Arr & Arr) loop
>        --  Error is "name expected"
>        null;
>     end loop;
> 
> end Pro;

There is clearly a compiler error (I get the same errors with GNAT 9.2.1). If I 
comment out the rejected cases, I get

$ gnatmake pro.adb
x86_64-linux-gnu-gcc-9 -c pro.adb
pro.adb:3:24: "others" choice not allowed here
gnatmake: "pro.adb" compilation error

as I expected. The declaration of Arr is invalid. The compiler should have 
reported that error even if some of the loops are invalid.

If I change line 3 to

    Arr : Int_Array (1 .. 10) := (others => 0);

then it still complains about the last 2 loops. I'm not familiar enough with the 
"of" syntax to know if that's expected or another compiler error.

-- 
Jeff Carter
"Friends don't let friends program in C++"
Zalman Stern
114