4 replies to this topic

[nickknack]

Hi guys,

I'm new to programming and just starting out in Haskell, and I came across \\ in some code. I've been unable to search for what it does because search engines do not recognise it as a word. Can someone help me out?

Thanks! :)

[gregwarner]

In Haskell, the backslash ('\') character is used to represent lambda functions. A double backslash is an escaped backslash, i.e., a way of representing a literal backslash character.

[Tyapka]

Well I guess gregwarner's answer was not helpful. It was not for me anyway.

(\\) (double backslash) function in Haskell is a list difference function as found in Data.List module (Data/List.hs)

Implementation:

(\\) :: (Eq a) => [a] -> [a] -> [a]
(\\) = foldl (flip delete)

It accepts 2 lists and deletes the first occurrence of each element of the second list from the first list.

Examples:

(\\) [1,2,3] [2,3,4]
> [1]

(\\) [1,2,3,4,5] [2,3,4]
> [1,5]

(\\) [1,2,2] [2]
> [1,2] -- See how only one "2" is deleted from the original list.

[Sysop_fb]

Hoogle

Hoogle for all your haskell function searching needs.

[gregwarner]

Thanks for the correction. Got mixed up there.