Zipping (computer science)

In computer science, zipping is a function which maps a tuple of sequences into a sequence of tuples. This name zip derives from the action of a zipper in that it interleaves two formerly disjoint sequences. The inverse function is unzip. Given the three words cat, fish and be where |cat| is 3, |fish| is 4 and |be| is 2. Let denote the length of the longest word which is fish; . The zip of cat, fish, be is then 4 tuples of elements: where # is a symbol not in the original alphabet. In Haskell this truncates to the shortest sequence , where : zip3 "cat" "fish" "be" [('c','f','b'),('a','i','e')] Let Σ be an alphabet, # a symbol not in Σ. Let x1x2... x|x|, y1y2... y|y|, z1z2... z|z|, ... be n words (i.e. finite sequences) of elements of Σ. Let denote the length of the longest word, i.e. the maximum of |x|, |y|, |z|, ... . The zip of these words is a finite sequence of n-tuples of elements of (Σ ∪ {#}), i.e. an element of : where for any index i > , the wi is #. The zip of x, y, z, ... is denoted zip(x, y, z, ...) or x ⋆ y ⋆ z ⋆ ... The inverse to zip is sometimes denoted unzip. A variation of the zip operation is defined by: where is the minimum length of the input words. It avoids the use of an adjoined element , but destroys information about elements of the input sequences beyond . Zip functions are often available in programming languages, often referred to as . In Lisp-dialects one can simply the desired function over the desired lists, is variadic in Lisp so it can take an arbitrary number of lists as argument. An example from Clojure: `nums' contains an infinite list of numbers (0 1 2 3 ...) (def nums (range)) (def tens [10 20 30]) (def firstname "Alice") To zip (0 1 2 3 ...