a calendar clearing for functional wanderers

haskell.day

Begin where the domain dot glows. Follow the lichen path through small lessons pinned under leaves, roots, and runnable ideas.

main :: IO ()

Specimen 01

Pure Function Spring

A pure function is clear water: same stones in, same ripples out. No hidden swamp creature changes the result.

double :: Int -> Int
leaf vein equals lambda
f x == f x
match

Pattern Match the Mushroom

Shape decides the spell

Each cap opens by constructor. The forest does not ask where a value came from; it studies the shape it has now.

taste MaybeSugar = case MaybeSugar of

Bog Crossing: Bind

Step only where the marshlight answers

Bind composes a walk where each next stone appears after the previous result. Context stays around your boots.

path = jar >>= inspect >>= name
Maybe

Canopy Note: Laziness

Spores wait for rain

Haskell can name an infinite vine without harvesting every leaf. Values wake when the lesson reaches them.

take 5 [1..]
defer • share • unfold
Eq (==)
Functor map
Monad bind

Cairn: Typeclass

Tagged stones for shared behavior

A typeclass is a goblin drawer label: many specimens, one known ritual. Find the label and you know what spell is safe.