Anonymous Functions

Anonymous functions (lambda functions) are expressions that represent a function without name.

\x -> x + 5     -- defines anonymous function that, given a x, returns x + 5

(\x -> x + 5) 3 -- applies the anonymous function over 3
8

Function with name:

double x = 2 * x    -- equals to double = \x -> 2 * x

double 3
6

map double [1, 2, 3]
[2, 4, 6]

map (\x -> 2 * x) [1, 2, 3]
[2, 4, 6]

Anonymous functions are usually used when they are short and only used once. They are also useful for performing program transformations.

Multiple parameters:

\x y -> x + y

Equals to:

\x -> \y -> x + y

Which means

\x -> (\y -> x + y)