# 4d47's solution

## to Flatten Array in the Clojure Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Take a nested list and return a single flattened list with all values except nil/null.

The challenge is to write a function that accepts an arbitrarily-deep nested list-like structure and returns a flattened structure without any nil/null values.

For Example

input: [1,[2,3,null,4],[null],5]

output: [1,2,3,4,5]

## Source

Interview Question https://reference.wolfram.com/language/ref/Flatten.html

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### flatten_array_test.clj

``````(ns flatten-array-test
(:require [clojure.test :refer [deftest is testing]]
[flatten-array]))

(deftest flattens-array-of-ints
(testing "flattens array with just integers present"
(is (= [1 2 3 4 5 6 7 8]
(flatten-array/flatten [1 [2 3 4 5 6 7] 8])))))

(deftest five-level-nesting
(testing "5 level nested list"
(is (= [0 2 2 3 8 100 4 50 -2]
(flatten-array/flatten [0 2 [[2 3] 8 100 4 [[[50]]]] -2])))))

(deftest six-level-nesting
(testing "6 level nested list"
(is (= [1 2 3 4 5 6 7 8]
(flatten-array/flatten [1 [2 [[3]] [4 [[5]]] 6 7] 8])))))

(deftest six-level-nested-with-nils
(testing "6 level nested list with nil values"
(is (= [0 2 2 3 8 100 -2]
(flatten-array/flatten [0 2 [[2 3] 8 [[100]] nil [[nil]]] -2])))))

(deftest all-nils-list
(testing "All values in nested list are nil"
(is (empty?
(flatten-array/flatten [nil [[[nil]]] nil nil [[nil nil] nil] nil])))))``````
``````(ns flatten-array
(:refer-clojure :rename {flatten flat}))

(defn flatten [x]
(filter some? (flat x)))``````