[Haskell-cafe] Monad transformer responsibilities
lemming at henning-thielemann.de
Sun Jun 7 16:42:22 EDT 2009
Stephan Friedrichs schrieb:
> it's alomost the same problem when you're writing a library with
> optional quickcheck test cases: Where to put the Arbitrary instances?
> - You can't put them into quickcheck
> - You don't want to put them in the library (because of the quickcheck
... and because there are two incompatible QuickCheck versions.
> - So you have to declare them near the test cases and they're orphan
> The entire project doesn't issue a single warning when compiling with
> -Wall *except* two orphan instances when building the test cases...
However, I had sometimes the case, where a type from another library was
part of my tests and thus I needed its Arbitrary instance. I could have
defined instances for the foreign types, but they would have been orphan
and I risk that the library author decides to add the instances later.
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