Implementing a counter in for

Question

I would like to iterate over a collection and at the same time also maintain a counter ex

(for [x (range 10) y (inc 0)] [x y] )

I would like 'y' to represent the counter, so for every element the output is ( [0 0] [ 1 1] [2 2]...). How do I do that?

Answer 1

You can use indexed from clojure.contrib.seq. Example:

(indexed '(a b c d))  =>  ([0 a] [1 b] [2 c] [3 d])

You can also use map-indexed. Example:

(map-indexed vector "foobar")  =>  ([0 \f] [1 \o] [2 \o] [3 \b] [4 \a] [5 \r])