Ryan Ingram wrote:
It's pretty simple, I think.
type ExpGen = ReaderT [String] Gen
arbExp :: ExpGen Expression
-- exercise for the reader
instance Arbitrary Expression where
arbitrary = runReaderT arbExp []
coarbitrary = coarbExp
coarbExp (Var s) = variant 0 . coarbitrary s
coarbExp (Apply a b) = variant 1 . coarbitrary a . coarbitrary b
coarbExp (Lambda s e) = variant 2 . coarbitrary s . coarbitrary e
instance Arbitrary Char where
arbitrary = elements "abcdefghijklmnopqrstuvwxyz_"
coarbitrary = coarbitrary . fromEnum
o_O
I love the way other people have wildly different ideas of "simple" than
me. I'm staring at this and completely failing to comprehend it. (But
then, anything with "co" in the name generally makes little sense to
me...) Why on earth would you need a reader monad? Surely if you want to
add bound variables and then later query what variables are bound, you'd
want a state monad? Hmm, I'm completely lost here.
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