A functional solution

Let's try to be more general: after all, requiring that some function or other be executed only once, isn't that outlandish, and may be required elsewhere! Let's lay down some principles:

• The original function (the one that may be called only once) should do that thing, and no other
• We don't want to modify the original function in any way
• We need to have a new function that will call the original one only once
• We want a general solution that we can apply to any number of original functions

The first principle listed previously is the single responsibility principle (the S in S.O.L.I.D.), which states that every function should be responsible over a single functionality. For more on S.O.L.I.D., check the article by Uncle Bob (Robert C. Martin, who wrote the five principles) at http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod.

Can we do it? Yes; and we'll write a higher-order function, which we'll be able to apply to any function, to produce a new function that will work only once. Let's see how!