04_flat.org

* flatten
  Implement =flatten=, a function that removes (flattens out) nested structure.

  Examples:

  : [1, 2, [3, 4]]   --> [1, 2, 3, 4]
  : [[1, 2], [3, 4]] --> [1, 2, 3, 4]

  Use any language and data structure/representation that makes sense. Go for the basic behavior first, but see bonus implementation notes for ideas.

** Bonus implementation ideas:
   These are of varying difficulty. Depending on your experience/skill, try some of these variants.

   1. Handle arbitrarily deep nesting (e.g. =[[[[1], [2, 3]]]] -> [1, 2, 3]=)
   2. Allow an extra argument that sets the number of levels to flatten
   3. Support any combination of iterables as input
   4. Implement a unit test suite
   5. Write a version with no loop constructs
   6. Write a version in a pure functional style
   7. Write a version with no recursive calls
   8. Write a version you'd deploy into production. Explain your choices for the production version.
   9. Implement a property-based testing suite (using e.g. jsverify)