HaloO, On Friday, 23. October 2009 02:27:00 Darren Duncan wrote: > Thinking further, my interpretation of what you said above is that the > Rational role is now basically saying that a number is represented in terms > of numerator/denominator and that certain operators are supported, but now > it is sounding like the details of whether the operators will produce > Rational results or Num results is now determinable on a per-class basis, > so we may end up working with types like "Rat32", "Rat64", "BigRat" (just > this one being unlimited precision), etc after all.
I believe that the thing people that don't care about the precision should use in sigs and variable declarations is the Rat role. That is I think that Rat should be the role that is currently named Rational. More specific instantiations of that role are then written in my proposed type signature invocant slot syntax as Rat[Rat64:]. Note that this is no problem because e.g. 'my Rat $x = 3/4' doesn't require Rat to be an instantiable class. Actually the class that implements Rat is chosen by the compiler to be e.g. Rat64. Then there need to be installation time defaults, command line switches and lexical pragmas to influence this choice. The second thing that needs to be hookable to different classes is the handling of overflow and underflow of e.g. Rat64 to either upgrade to BigRat or wrap the offending value back into Rat64 or switch over to Num. Then there is the problem of mixed precision cases etc. > Presumably then with the Integer role we'll also have types like "Int32", > "Int64", "BigInt" that do the role and also convert to a Num when their > bounds are exceeded? > > Does that sound about right? Yes. I think there should be an Int role and classes implementing it. The Int role must be a subrole of Rat. E.g. it adds the bit manipulation operators which are difficult to define for rationals if not outright meaningless. This subroling is needed for calling Rat routines with an Int, of course. From a Huffman POV the roles for generic integers and rationals must be short, so the Numeric and Rational roles in S32 are going in the wrong direction. Regards, TSa. -- "The unavoidable price of reliability is simplicity" -- C.A.R. Hoare "Simplicity does not precede complexity, but follows it." -- A.J. Perlis 1 + 2 + 3 + 4 + ... = -1/12 -- Srinivasa Ramanujan
