Re: U : Unbounded_String := "bla bla bla"; (was: Is the Writing...)

["Robert I. Eachus" <rieachus@comcast.net>]

Randy Brukardt wrote:
> "Robert I. Eachus" <rieachus@comcast.net> wrote in message
> news:3F88E067.30209@comcast.net...
> 
>>Now if you want to recommend that in Ada 200X, package
>>Ada.Strings.Unbounded include:
>>
>>    function "+" (Source : in String) return Unbounded_String
>>       renames To_Unbounded_String;
>>    function "+" (Source : in Unbounded_String) return String
>>       renames To_String;
>>
>>I will certainly support that.  I don't really know why they were left
>>out of Ada.Strings.Unbounded while
> 
> 
> They were briefly in AI-301's improvements to Ada.Strings, but enough people
> think that they're ugly that they were taken out.

Foo: Unbounded_String := + "some_string"; -- is ugly?

Was anything offered as a non-ugly alternative?

And Russ still thinks there is some point to arguing for adding += to 
Ada?  Lots of luck Russ, but don't be surprised if many of us feel that 
you are Don Quixote tilting at windmills.

> No, actually it wouldn't. It would make a lot of existing code ambiguous.
> 
>   A : Unbounded_String;
>   B : Unbounded_String := A & "something";
> 
> Since the string literal could have either type String or Unbounded_String,
> and "&" can have operands of either type, the expression would become
> ambiguous.

Ouch! I forgot about that case when explaining why the non-literal 
conversions would be ambiguous.  Having worked on this though, you can 
handle it as you say by a completely new package with different 
overloadings of "&"--which won't happen.

-- 
                                                     Robert I. Eachus

"Quality is the Buddha. Quality is scientific reality. Quality is the 
goal of Art. It remains to work these concepts into a practical, 
down-to-earth context, and for this there is nothing more practical or 
down-to-earth than what I have been talking about all along...the repair 
of an old motorcycle."  -- from Zen and the Art of Motorcycle 
Maintenance by Robert Pirsig