# $

### From HaskellWiki

Revision as of 00:09, 1 October 2016 by Henk-Jan van Tuyl (Talk | contribs)

**$**is an infix operator often seen in Haskell code. It applies the function on its left to the value on its right. At first glance this operator appears redundant, since ordinary application

(f x)

(f $ x)

$

f $ g $ h x = f (g (h x))If

$

f g h x = ((f g) h) xIt is also useful in higher-order situations, such as

map ($ 0) xs

zipWith ($) fs xs

## 1 Definition

$ comes from the Prelude, where it is defined as:

infixr 0 $ ($) :: (a -> b) -> a -> b f $ x = f x

## 2 Note

The $ syntax is also used in Template Haskell with an entirely different meaning. If the $ is *immediately followed* by a letter or a left parenthesis (with no intervening white space), then it is understood by the GHC compiler as a Template Haskell splice and not the infix operator described above. To get the infix operator be sure to separate the $ from the right argument by at least one white space.