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<div>Hi haskellers, </div>
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<div>I am trying to understand why I get the following error in learning applicative style.</div>
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Prelude> let estimates = [5,5,8,8,2,1,5,2]</p>
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Prelude> (/) <$> Just $ foldl (+) 0 estimates <*> Just . fromIntegral $ length estimates</p>
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<interactive>:54:1:</p>
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Non type-variable argument in the constraint: Fractional (Maybe r)</p>
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(Use FlexibleContexts to permit this)</p>
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When checking that ‘it’ has the inferred type</p>
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it :: forall a r.</p>
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(Fractional (Maybe r), Num a, Num (Int -> Maybe a -> r)) =></p>
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Maybe r -> Maybe r</p>
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<div>All the parts work individually. If use let and assign the parts to x and y it also works.</div>
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<div>E.g. This works</div>
<div>let x = Just $ foldl (+) estimates</div>
<div>Let y = Just . fromIntegral $ length estimates</div>
<div>(/) <$> x <*> y</div>
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<div>I clearly do not understand exactly how these work. :-)</div>
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<div>Thanks for any help,</div>
<div>-wes</div>
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