N equivalent for the Zip function in Clojure Core or Contrib

clojure

In Clojure, I want to combine two lists to give a list of pairs, 

> (zip '(1 2 3) '(4 5 6))  
((1 4) (2 5) (3 6))

In Haskell or Ruby the function is called zip. Implementing it is not difficult, but I wanted to make sure I wasn't missing a function in Core or Contrib.

There is a zip namespace in Core, but it is described as providing access to the Zipper functional technique, which does not appear to be what I am after.

Is there an equivalent function for combining 2 or more lists, in this way, in Core?

If there is not, is it because there is an idiomatic approach that renders the function unneeded?

Best Answer

(map vector '(1 2 3) '(4 5 6))

does what you want:

=> ([1 4] [2 5] [3 6])

Haskell needs a collection of zipWith (zipWith3, zipWith4, ...) functions, because they all need to be of a specific type; in particular, the number of input lists they accept needs to be fixed. (The zip, zip2, zip3, ... family can be regarded as a specialisation of the zipWith family for the common use case of tupling).

In contrast, Clojure and other Lisps have good support for variable arity functions; map is one of them and can be used for "tupling" in a manner similar to Haskell's

zipWith (\x y -> (x, y))

The idiomatic way to build a "tuple" in Clojure is to construct a short vector, as displayed above.

(Just for completeness, note that Haskell with some basic extensions does allow variable arity functions; using them requires a good understanding of the language, though, and the vanilla Haskell 98 probably doesn't support them at all, thus fixed arity functions are preferrable for the standard library.)

Related Topic