Remember that foldr has flipped operator order from foldl.
:t foldl foldl :: Foldable t => (b -> a -> b) -> b -> t a -> b :t foldr foldr :: Foldable t => (a -> b -> b) -> b -> t a -> b
That means that you should expand them in the opposite order from how
it seems to read.
p >>= \x -> -- Just 1 >>= \ 1
q >>= \y -> -- return [] >>= \ []
return (1 : []) -- Just [1]
On Tue, Sep 26, 2017 at 12:59 PM, Jimbo
Hello everyone,
Just trying to understand the sequence function as follows:
sequence [Just 1]
-- evaluates to Just [1]
sequence = foldr mcons (return []) where mcons p q = p >>= \x -> q >>= \y -> return (x:y)
-- I'm trying to walk through the code as follows, I understand what is below isn't -- haskell code
p >>= \x -> [] q >>= \y -> Just 1 return (x:y) -- [] : Just 1
Am I thinking of sequence correctly here?
Best regards,
Jim
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