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

Ryan Ingram ryani.spam at gmail.com
Thu Dec 4 17:46:24 EST 2008

> 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").

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

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