th-dict-discovery: Automatically discover available dictionaries at compile time.
th-dict-discovery is a library to get your hands on the in-scope, concrete instances of a class. The motivating use-case is to generate property tests to automatically prove new instances of a class follow the laws.
This library uses Template Haskell to provide a list of existentialized
for each concrete (entirely monomorphic) instance in scope.
defInstances :: [SomeDict1 Default] defInstances = $(someDicts ''Default)
These lists can be consumed via
withSomeDict1 :: (forall a. c a => Proxy a -> r) -> SomeDict1 c -> r, for
example, we can generate hspec tests:
spec :: Spec spec = describe "each default instance" . forM_ defInstances $ withSomeDict1 $ \(_ :: Proxy a) -> it "shouldn't be undefined" $ seq (def @a) True `shouldBe` True
The library also defines up to
SomeDict8, with eliminators up to
withSomeDict8. These correspond to multi-parameter typeclasses with
first-order, potentially polykinded parameters.
The TH function
someDicts is smart enough to generate the correct arity of
SomeDictN for the class under inspection, but at this time, you're responsible
for using the correct
withSomeDictN to consume it.
|Dependencies||base (==4.9.*), constraints, template-haskell [details]|
|Source repo||head: git clone https://github.com/isovector/th-dict-discovery.git|
|Uploaded||by isovector at Wed Dec 27 09:54:45 UTC 2017|
|Downloads||240 total (3 in the last 30 days)|
|Rating||2.0 (votes: 1) [estimated by rule of succession]|
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