Anonymous Functions in Haskell

Introduction

It’s no doubt that when you’re first entering the wild world of Haskell, that it’s syntax is a little alien to look at, at first glance. Once of the major building blocks or keys to unlocking power in Haskell are anonymous functions. The idea of higher-order functions in languages these days is becoming more of a standard rather than a feature and Haskell is no exception. There’s plenty around on the web to read about anonymous functions, higher-order functions and of course [functional programming](http://en.wikipedia.org/wiki/Functional_programming.

An example

A fairly unintuitive example, but shows how you can assign an anonymous function to a handleable variable is shown:

let y = (\x -> x)

Breaking this down, the key part is (\x -> x). Immediately, you can see that anonymous functions take the form of (\param1 .. paramn -> body). The real power here is unlocked when you use an anonymous function in conjunction with other functions. The best example I think is the use of the map function. The map function is defined as follows:

map :: (a -> b) -> [a] -> [b]
map f xs = [f x | x <- xs]

This definition says, give me a function f and I’ll take all of the a’s and turn them into b’s. Obviously, the anonymous function comes in for the f component. For simplicity, a can be an array of integers.

map (\x -> x * x) [1,2..100]

So the above example maps the function (x*x) across an array from 1 to 100. Easy!