Instances for data types

Simon Marlow simonmar at
Fri Apr 30 10:49:01 EDT 2004

On 27 April 2004 20:58, Sven Panne wrote:

> Playing around with System.Posix.Terminal, I realized that there are
> no Read, Show, Eq, Enum, ... instances for the data types defined
> there (TerminalState, TerminalMode, ...). This is not a very
> difficult problem to solve in one's 
> own program, but it's not very handy, either.

By all means go ahead and add these instances.

> This raises a general
> question: What instances should be defined in the standard libraries
> for types like 
> this? A general policy would be a good thing. IMHO, at least Read,
> Show, Typeable and Eq could be expected, having Ord, Enum and
> Bounded, too, would be nice. 

Good point.  I've been meaning to create a separate document so we have
somewhere to collect general library policies like this.  It's on my


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