[Haskell-cafe] manage effects in a DSL
daniel.trstenjak at gmail.com
Mon Feb 10 16:10:01 UTC 2014
On Mon, Feb 10, 2014 at 04:55:52PM +0100, Dominique Devriese wrote:
> Hm. Interesting point, I guess this is the same problem as the whole
> orphan instances debate... I didn't think of the connection to that
> problem. Still, I'm convinced there are situations where local
> instances are *exactly* what we need, so there must be some way to
> avoid this problem...
If a type class has a clear semantical meaning, what should then
be the point of having multiple instances for the same data type?
A clear semantical meaning contradicts multiple instances, they would
only make reasoning about your code harder.
The few use cases where it might be nice to be able to define a new
instance aren't IMHO worth the drawbacks.
You would just open Haskell for Ruby like monkey patching.
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