Re: [Haskell-beginners] How to avoid repeating a type restriction from a data constructor

Daniel Fischer writes:

...

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data Source x y where

Source :: Variable v => { bindings :: v [Binding a], var :: v a }

-> Source v a

I tried this, but every place that I remove the restriction Variable v => from something using Source, I get an error No instance for (Variable v) ...

Sounds like you're not pattern-matching on the `Source` constructor.

Can you post some example code?

http://code.accursoft.com/binding/src/c13ccbbec0ba8e326369ff2252863f20a891ef... http://code.accursoft.com/binding/src/c13ccbbec0ba8e326369ff2252863f20a891ef...