- February 8th, 2018: We have maybe :: b -> (a -> b) -> Maybe a -> b. But we don't have list? Or do we? Define list:

list :: b -> ([a] -> b) -> [a] -> b

list nullanswer flist lst = undefined - BONUS: Both Maybe a and [a] are binary types, ... so is MonadPlus:

Maybe a = Nothing | Just a

List a = Cons a (List a) | Nil

MonadPlus m => mzero | m a `mplus` m a

Is there some generalization that maybe and list are functions of? What is that generalization? - February 6th, 2018:

You have f :: a -> [b] -> [c]

But instead of just one a you have [a]

Define g :: [a] -> [b] -> [c]

in terms of f - Daniel @leptonyu g as bs = foldl (\xs a -> f a bs ++ xs) [] as
- ptdr_bot @m0rth0n g as bs = flip f bs =<< as
- Victoria C @ToriconPrime g as bs = concat $ fmap ($ bs) (fmap f as)
- matt @themattchan g = flip $ concatMap . flip f
- Nicoλas @BeRewt g = flip (flip (>>=) . flip f) Or: g as bs = as >>= flip f bs
- Sangeet Kar @sangeet_kar g = foldMap f

## Friday, April 13, 2018

### February 2018 1 Liner 1HaskellADay Problems and Solutions

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