In this challenge you'll produce a Set. We're defining the Set as "a function that accepts a number and returns a boolean." Or, in a fancier looking notation:

type Set = Function(Integer) => Boolean

Your Sets will only contain integers.

As you produce functions, consider if they can be combined to implement others. In other words, can you implement some function in terms of another? Look for and take advantage of these opportunities when appropriate.

You'll need to write tests for each method you implement. You can run your tests with node sets_test.js.

Define and test the following methods stubbed out in sets.js:

• singletonSet
• union
• intersect
• diff
• filter

You have the basic set operations, now we want operations that can operate on the elements in the sets.

• forall
• exists
• map
• toString

You'll notice these methods only operate on bounded integers. Why is this necessary? Describe your thoughts in note.md.