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oisdk/isPal.hs

Created May 8, 2019 00:13
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isPal.hs
isPal :: forall a. Eq a => [a] -> Bool
isPal xs = getAll (fst (go xs xs)) where
go (y:ys) (_:_:zs) = f y =<< go ys zs
go (_:ys) [_] = pure ys
go ys [] = pure ys
f y ~(z:zs) = (All (y == z), zs)
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