Robert Dockins
i would argue against treating tuples as pure syntactic sugar for nested pairs; since the nesting carries hierarchical information, i would expect (x,y,z) used in place of (x,(y,z)) to cause an error.
Indeed, quite apart from anything else, transforming tuples into nested tuples changes the performance of access from constant-time into linear-time (using the right-nested transformation specified by Robert), or at best, log-time (using a balanced tree schema). This is highly undesirable.
The copout (in my opinion) is the current system where tuples are defined up to some set n (64 in GHC I think -- the report only mandates 15), and if you want bigger tuples you're SOL.
To address this problem, I think we should permit user-definition of tuple constructors with the expected syntax e.g. (,,,,,), which is already accepted by at least some compilers (nhc98,yhc).
More disturbing is the complete inability to write general functions over tuples. The only fully general solution is to use something like template haskell which 1) is overkill 2) has ugly syntax (sorry but it's true) 3) GHC only and 4) hard to learn.
I don't believe you need to invoke the full awesome majesty of Template Haskell in this case. Surely plain -fgenerics will suffice? I am hoping that some simple form of data-type generics will make it into the new standard. Regards, Malcolm