Extended Type Design.

[Andrei Alexandrescu (See Website For Email)]

Deewiant wrote:
> Benji Smith wrote:
>> And the word "super" is now overloaded in two completely unrelated concepts.
>>
> 
> Which isn't that rare, see the following link:
> http://www.prowiki.org/wiki4d/wiki.cgi?LanguageSpecification/KeywordIndex
> 
> I find the following examples: auto, in, is, mixin, scope, static.
> 
> I have come to abhor the keyword "static" largely due to the above. Too bad its
> various uses are unavoidably useful. <g>
> 
> But I do agree with you, in a way. After writing the following I find my
> explanation somewhat unclear even to myself, but bear with me.
> 
> The problem with "super const" is that "super" modifies the other keyword,
> "const", instead of saying something about the expression/statement/whatever (in
> this case, the type). Even "static", in all its horror, can be seen as
> specifying one of "module-level" or "compile-time". The other keywords mentioned
> above use their English meaning as such an explanation, and so can be understood
> without too much thought. "super const" would make "super" another "static":
> lacking context, you can't be sure about about even the general meaning, let
> alone the one in a specific instance.
> 
> Upon reflection it may be moot, since one probably rarely cares about keywords'
> meanings without context, but I'm sure some psychologist could come up with
> something about intuitiveness which affects coding speed, or whatever.

Working in NLP myself, I totally disagree. Natural language is rife with 
homonimy and synonimy, and we're all very, very happy with that. But in 
this case we don't even have to go that far: "super" is an adjective 
meaning primarily "of high grade or quality" and qualifies a noun. If 
there's no noun, you don't know what is "of high grade or quality". It's 
a fact, and we don't even blink.

The reality behind super const is that it expresses a stronger form of 
const. It makes a lot of sense if I dub it "super const" in natural 
language, to express it in the same way in the programming language. I 
thought that that's too verbose and devised "const!" as a shortcut 
(again with obvious conotations in natural language), but I'm thinking 
of dropping it and let type inference add "super" to "const" whenever it 
can. That should ensure exactness of the type system without verbosity 
in source code.

> I'd be happiest to just get the feature as soon as possible; worrying about
> keyword semantics can come later. Just like the abominations beginning with
> "on_scope_". <g>

Great idea. :o)


Andrei