arliss_obsidian/fp/Language/Functions/Currying.md

Functions are curried in PureScript, meaning that "a function of 2 arguments" is actually "a function of 1 argument, returning a function of 1 argument."

This allows you to call many functions point-free, and think in terms of "building up to a conclusion" rather than "i need everything at once."

e.g.

add :: Int -> Int -> Int
-- ... 

add2 :: Int -> Int
add2 n = add 2 n

is equivalent to

add :: Int -> Int -> Int
-- ... 

add2 :: Int -> Int
add2 = add 2

Walking through this:

add has type Int -> Int -> Int

if we give add a single Int argument, it will return a function of type Int -> Int. This function is the "second half" of add, waiting for it's second argument. Since Int -> Int is the type of add2, we can simply say add2 = add 2.

[!info] as a rule, any time a function's last argument is passed as the last argument to another function, you can remove both.

f a = g b c a

\a -> g b c a

f a = g $ h a

can be written as

f = g b c

g b c

f = g <<< h