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]
You can think of this data structure as a Rose Tree
. You are given a data type 'a tree
that represents this data structure.
Notes
Empty
represents null
List [...]
.List [Elem 1, List [Elem 2, Elem 3, Empty, Elem 4], List [Empty], Elem 5]
Sign up to Exercism to learn and master Standard ML with 61 exercises, and real human mentoring, all for free.