🚀 go-pugleaf

butrfeld@swift.cs.tcd.ie writes:

>Can anyone explain the following aspect of the Miranda and Haskell type
>systems that I find annoying ? Is there a theoretical reason for it ?
>
>pairs, triples, quintuples, etc.. are _distinct_ types. In particular,
>(a,(b,c)) != ((a,b),c) != (a,b,c).

A practical reason is to give the implementation freedom to implement
triples etc. as efficiently as possible. Requiring (a,b,c) to be stored
in the same manner as (a,(b,c)) might require an extra level of indirection
(and type equivalence usually implies storage equivalence).

Theoretically I see no reason why (a,b,c) should be required to be
equal to say (a,(b,c)). That seems like implementation details to me.
It's also very assymetric - you have to require either left-pairing
or right-pairing, and there is no obvious reason to prefer one over the
other. It makes perfect sense to me that (a,b,c) is quite simply not a
pair!

-- 
Fergus Henderson             fjh@munta.cs.mu.OZ.AU      
This .signature virus is a self-referential statement that is true - but 
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