• "Arlen" <arlen.ng gmx.com> Oct 06 2012
• "David Nadlinger" <see klickverbot.at> Oct 06 2012

"Arlen" <arlen.ng gmx.com> writes:

I'm not sure if TypeTuples work well when doing things like dimensional
analysis.  For example, if you have two TypeTuples, A and B, what would the
signature of the metafunction to merge the two look like?

template Merge(A, B) { }

won't work, and neither will

template Merge(alias A, alias B) { }

and you certainly can't do something like

template Merge(AB...) { }

Arlen

 
  ----- Original Message -----
  From: Jonathan M Davis
  Sent: 10/06/12 12:52 PM
  To: digitalmars.D
  Subject: Re: Preliminary submission - std.rational and std.typelist
 
   
On Saturday, October 06, 2012 19:03:39 Arlen wrote:
 I wasn't aware that we already had std.typelist module in Phobos until I was
 ready to submit my work. I suppose the work was abandoned or it was never
 finalized? There are differences in typelist2.d and typelist.d, though.


It needs to be removed. It's not even compiled in. std.typetuple is what we 
use. I would suggest looking at adding further functionality to it rather than 
trying to create anything based on type lists. TypeTuples can do the same 
things and are actually more flexible.

- Jonathan M Davis
   

"David Nadlinger" <see klickverbot.at> writes:

On Saturday, 6 October 2012 at 18:13:19 UTC, Arlen wrote:
 For example, if you have two TypeTuples, A and B, what would 
 the signature of the metafunction to merge the two look like?


In my experience, these cases occur a lot less frequently than 
one might think when first encountering the problem. The solution 
I usually go for is to just define a ConfinedTuple (or something 
like that) template:

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

template SomeAlgorithm(alias A, alias B) {}
---

Then, call that one algorithm using 
SomeAlgorithm!(ConfinedTuple!A, ConfinedTuple!B). At least to me, 
it seems to be the better tradeoff compared to re-implementing 
all the TypeTuple functionality for another compile-time tuple 
type.

David