[Haskell-cafe] How to define Show [MyType] ?

[Jonathan Cast]

On Thu, 2008-12-04 at 14:46 -0800, Ryan Ingram wrote:
> > If you really, really wanted to define Show [ShipInfo], then putting
> >
> > {-# LANGUAGE FlexibleInstances, OverlappingInstances #-}
> >
> > at the beginning of your file would work.  At the cost of using
> > overlapping instances, of course.
> 
> And at the cost of causing code like this:
> 
> > f :: Show a => [a] -> String
> > f xs = show xs
> 
> to fail to compile (see "Incoherent Instances").

Right.

> Implement "showList"; it's the Right Answer for this case.

Yeah.

jcc