On 29 May 2008, at 1:30 AM, Neil Mitchell wrote:
Hi
Following this line of reasoning: why is 1 syntactic sugar for fromIntegral 1? If 1 has type Integer then the generic value is just a fromIntergal away!
That's a good point the other way --- I suspect, like most things Num, numeric literals were rather grand-fathered in than designed intentionally that way.
fromIntegral is essential if you have two "integer" types, namely Int and Integer. If you are looking for something to blame, then its the premature optimisation that is Int. Int is really just a performance hack around Integer.
Um, that de-railed quickly... ‘fromIntegral’ in the original is a typo or mis-understanding for ‘fromInteger’. My comment was re: implicit fromInteger (and polymorphic numeric literals). GP was arguing for making Map.lookup polymorphic in the failure monad; I replied I thought, in the case of numeric literals, that no-one designing Haskell without the tradition that 3 `member` IR, no-one would have thought that 3 :: Integer and 3 :: Double both made sense. Explicit conversions are not really the issue here. jcc