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HASKELLER

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I / Lambda Corridor

Types

Before a value speaks, its shape is already written in the margin.

kindIntTextMaybeEitherFunctorMonad
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II / corridor

Functions

A function is a lit passage between two rooms of possibility.

aa → bb compose :: (b -> c) -> (a -> b) -> a -> c

III / corridor

Composition

Two circuits remember they were always a single sentence.

(.) :: (b -> c) -> (a -> b) -> a -> c

The Monad Chapel

laws suspended in violet dark

returnηreturn a >>= k ≡ k a
bind>>=m >>= return ≡ m
joinμjoin . fmap join ≡ join . join
Monad m => m a -> (a -> m b) -> m b

The signal enters a context, touches a function, and exits still carrying the shape of its world.

>>=
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map :: (a -> b) -> [a] -> [b]

Apply one transformation to every inhabitant of a list.

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

Collapse a procession into a remembered value.

(<$>) :: Functor f => (a -> b) -> f a -> f b

A function lifted into a container's weather.

(>>=) :: Monad m => m a -> (a -> m b) -> m b

Sequential binding: a corridor whose door creates the next corridor.

traverse :: (Traversable t, Applicative f) => (a -> f b) -> t a -> f (t b)

Walk a structure while preserving the ritual order of effects.

pure :: Applicative f => a -> f a

Place a bare value into the ceremonial frame.

λ>

The types will guide you.