Re: Ada and string literals

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

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> On Fri, 01 Feb 2013 08:20:24 -0500, Stephen Leake wrote:
>
>> That's what "+" is for:
>> 
>>    function "+" (Item : in String) return access constant String
>>    is begin
>>       return new String'(Item);
>>    end "+";
>> 
>>      Colors : constant String_Sequence :=
>>          (+"red", -- This _is_ Ada!
>>           +"orange",
>>           +"dark green",
>>           ...);
>
> What about:
>
>    function "&" (Left, Right : String) return String_Sequence is
>    begin
>       return (new String'(Left), new String'(Right));
>    end "&";
>
>    function "&" (Left : String; Right : String_Sequence)
>       return String_Sequence is
>    begin
>       return String_Sequence'(1 => new String'(Left)) & Right;
>    end "&";
>
>    Colors : constant String_Sequence := "red" & "orange" & "dark green";

Looks dangerous to me.  If I'm not mistaken, you have a bug:  ;-)
the above sets Colors to a 2-element array containing a pointer
to "redorange" and a pointer to "dark green".  The first "&" in Colors
calls the predefined String one, and the second "&" calls the first
"&" body shown above.  The second body is never called.

I suppose that could be fixed, but we're getting further and
further from something where the compiler is likely to generate
a statically-allocated table of pointers to statically-allocated
strings.

- Bob