Question

I want to create a sequence, however to create its every element I need access to the two previous elements. What is the generic way to do such things in clojure ?

So two slightly diff cases –
a) seq is (a b c) when I am processing c I want to have access to a and b ….
b) and having such ability to create the sequence itself by always being able to access th two previous elements.

Thanks,
Murtaza

Answer 1

You can iterate using a vector of two elements and then take the first of the resulting sequence.

For example, to create the fibonacci series:

user=> (def fib (map first (iterate (fn [[a b]] [b (+ a b)]) [1 1])))
#'user/fib

user=> (take 10 fib)
(1 1 2 3 5 8 13 21 34 55)