Instances for BaudRate from System.Posix.Terminal

[Stephan Friedrichs]

On 26/04/11 10:19, Heka Treep wrote:
> Hi, the c-libraries use BaudRate as integers, so how about to add Enum
> instance for BaudRate? It allow users to use fromEnum, toEnum methods.
> 
> Like this:
> 
> module System.Posix.Terminal (
> ...
> 
> data BaudRate
>   = B0
>   ...
>   | B115200
>   deriving ( Eq, Ord )
> 
> instance Enum BaudRate where
>   fromEnum b = case b of
>     B0      -> 0
>     B50     -> 50
>     B75     -> 75
> [...]
>   toEnum i = case i of
>     0       -> B0
>     50      -> B50
>     75      -> B75
> [...]

This way, the default implementations of
 - succ, pred
 - enumFrom, enumFromTo, enumFromThen, enumFromThenTo
will fail, because, e.g. succ B0 ~> toEnum (0 + 1) ~> error ...
Do you want succ B0 to be B50? Does [B0,B75..] make sense?

//Stephan