[Haskell-beginners] Re: Apparent bug

Yitzchak Gale gale at sefer.org
Tue Nov 16 15:53:02 EST 2010

Edward Z. Yang wrote:
> It seems to me that there is a possibility we could reify some information
> that is traditionally specified in the documentation: that is, what
> functions must be defined by a minimal instance, which could then give
> GHC enough information to give meaningful warnings if not all functions
> for a minimal instance are provided.

It definitely should not be so easy to create runtime crashes
by not providing enough method implementations at compile

In this case, though, showsPrec and readsPrec only exist for
historical reasons. Nowadays I don't think anyone would
consider ReadS or ShowS for a parser or pretty-printer
so complex that it needs to consider operator precedence.
It would be better to deprecate them and remove them,
together with the default method implementations for
shows and reads.


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