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russmatney/lens-op-ob-hasntexample.hs

Last active May 20, 2018 16:55
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lens-op-ob-hasntexample.hs
hasn'tExample :: IO ()
hasn'tExample = do
let bob = User (UserName "bob") 42 Nothing HM.empty
print "Hasn't bob gold in his inventory?"
print $ hasn't (inventory . ix "gold") bob
-- True
-- As in, "Yes, he doesn't."
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