[Haskell-cafe] instance Enum [Char] where ...

[Thomas Davie]

Am 30.12.2008 um 04:25 schrieb JustinGoguen:

> I am having difficulty making [Char] an instance of Enum. fromEnum  
> is easy
> enough: map fromEnum to each char in the string and take the sum.  
> However,
> toEnum has no way of knowing what the original string was.

The problem you're having is that your implementation does not  
correctly enumerate lists of characters – in order to do so correctly,  
you must not create the clashes you get with (for example "ab" and  
"ba").

I'd suggest rethinking how you would enumerate such strings.

Bob