[Haskell-cafe] (Feeling that) GHCi is trying to protect me from myself with overlapping instances and existential types

Tom Ellis tom-lists-haskell-cafe-2017 at jaguarpaw.co.uk
Sun Feb 16 16:02:17 UTC 2020

On Sun, Feb 16, 2020 at 03:46:25PM +0000, Juan Casanova wrote:
> This may be an argument in favour of your notion, that any kind of overlap
> is wrong by definition and it just so happens that it only flags up when
> used. I'd still love some comment from someone with a bit more authority
> about this.

This is an area where an expert language designer needs to chime in I
think and they don't tend to hang out on haskell-cafe.

If you are trying to solve a practical problem, then based on the
discussion so far I am around 90% confident that you would be better
off without using typeclasses at all.  How would your design look if
you just passed around first class values instead?


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