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

[retard]

Fri, 25 Feb 2011 12:18:11 -0800, Jonathan M Davis wrote:

> On Friday, February 25, 2011 03:39:31 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.
>> 
>> 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?
> 
> If all you want is a normal tuple, use Tuple from std.typecons. It even
> has the convenience function tuple for creating them. TypeTuple is a
> different beast entirely, and you probably don't want that unless you
> specifically need it. It has to do with processing types and are _not_
> generally what you want. If what you're looking for is tuples, then use
> std.typecons.Tuple.

I've used:

template Tuple(T...) { alias T Tuple; }

Nicely built-in and works in most cases.