What are tuples exactly? (D's tuples considered harmful)

[Gary Whatmore]

Jesse Phillips Wrote:

> Morlan Wrote:
> 
> > While trying to understand the expand mechanism presented in the TDPL book I
> > tried to read std.typetuple and std.typecons files. I found a true nightmare
> > in those files in the form of an almost infinite chain of aliases and macro
> > processing. How can one understand a written text if the words are redifined
> > in every other line? And people say that goto instruction is bad? Please give
> > me a break.
> 
> The aliases serve to simplify things. You would find it even more overwhelming if the true types were used. Aliases should show their base type in the documentation though.
> 
> > Anyway, at some point I realized that I cannot understand what is going on
> > because there is some language mechanism in action which I do not know. I
> > wrote a small program to confirm this. Here it is:
> > 
> > struct S { TypeTuple!(int, double) field; }
> > void main(){
> > 	S mys;
> > 	mys.field[0] = 4;
> > 	mys.field[1] = 4.4;
> > }
> > 
> > It compiles all right. But if you replace the S's definition with {int, double
> > field;}
> > it does not compile. So tuples are clearly much more than a sequence of types
> > and they trigger a completely different semantic action than a plain sequence
> > of types. Is there a precise definition of tuples somewhere?
> 
>  struct S { int, double field; }
> 
> Right, tuples have very little syntactic sugar. And frankly this wouldn't be the syntax I would want.
> 
> I don't think there is any good introduction to D tuples. The best way to think of them is to know they are compile time constructs. They are their purely to be manipulated during compilation and have no meaning at runtime. These types are made possible because of language features like templates, mixins, and alias parameters.
> 
> Another issue is that D isn't very strict. We have TypeTuple and Tuple, both of which can contain types and values. But it doesn't look like things will be changing.

Fuck no! "precise definition of tuples" is something that always makes me really grumpy. Do we want a incomprehensible ivory tower language or something practical? The D's tuples are a bit hazy. A bit harder to grok, but the good sides are better performance, flexibility and friendliness towards pragmatic c/c++ mentality. If you want something "better", go use Haskell an enjoy your 90% slower runtimes.

People always complain about missing documentation, but I don't care. Better developers don't need documentation, they value the tools. Walter spends 95% time on developing tools, 5% helping the community in this newsgroup and in conferences.