Enum class

[Pixel]

George Russell <ger@tzi.de> writes:

>   (1) succ & pred.  These appear for float to correspond to adding or subtracting
>       1.0.  (I am finding this out by testing with ghci; it's not specified where
>       it should be, in section 6.3.4 of the standard).   Because of rounding errors,
>       succ and pred fail many of the properties for float they have for integers, EG
>          succ . pred = pred . succ = id
>          succ x > x
>       and so on.

Quite a few pbs with overflow on Int too:

i :: Int
i = 0x7fffffff

i_plus_1 = i+1
  -- ghc : -2147483648
  -- hugs: -2147483648

i_succ = succ i
  -- ghc : *** Exception: Prelude.Enum.succ{Int}: tried to take `succ' of maxBound
  -- hugs: -2147483648

j :: Int
j = 0x80000000
  -- ghc : -2147483648
  -- hugs: Program error: {primIntegerToInt 2147483648}

k :: Int
k = 0x100000000
  -- ghc : 0
  -- hugs: Program error: {primIntegerToInt 4294967296}

i':: Integer
i'= 0x7fffffff
i_plus_1' = i+1
  -- ghc : 2147483648
  -- hugs: 2147483648

i_succ' = succ i'
  -- ghc : 2147483648
  -- hugs: -2147483648