[Haskell-cafe] Extensible Effects & Multiple Operations

Justin Bailey jgbailey at gmail.com
Mon Jul 21 16:02:56 UTC 2014


On Thu, Jul 17, 2014 at 3:32 PM, Tobias Florek <haskell at ibotty.net> wrote:
>     data OpenFile v = Read (Char -> v)
>                     | EOF  (Bool -> v)
>       deriving Typeable
>

That worked! Removing the type variable (`a`) from `OpenFile` did the
trick. I was carrying too much type information around for what I
wanted to do (e.g., OpenFile Char and OpenFile Bool). Removing that
extra piece of info allowed me to write `runOpenFile` just like I
wanted.

Thanks!

Justin


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