On Thu, 19 Oct 2000, Tom Pledger wrote:
If you had such a non-standard type, I imagine you'd also declare something like this:
instance Subtype Int8 Int16 where ... instance Subtype Int16 Int24 where ... instance Subtype Int24 Int where ...
and hence literals in the range -128 to 127 would be typed Int8, etc.
What would be the rule for typing integer literals? Currently it's simple: fromIntegral (number::Integer), and Int8 is a completely non-magical type. With your proposal, assume that the programmer makes a bunch of subtype declarations for his own types... What now? (Assuming that subtyping can be reasonably embedded in the Haskell's type system at all.) A more concrete example. Does 10 have type Int8 or Word8? Is Int8 a subtype of Word8, or the reverse? How could 10 be used as both Int8 and Word8? Current Haskell rules and not perfect: 12345::Int8 is legal. Conversions are explicit and there is no distinction between always safe conversions and those that may take an out of range parameter. But I'm happy with it; conversions are rarely used anyway, rules are simple, and there is no need of asking a question like: is every Int representable as Double (the answer may depend on the implementation). -- Marcin 'Qrczak' Kowalczyk