A Counter the Functional Way

Photo by Steve Johnson on Unsplash

There are many ways to create a counter; one way is the object-oriented programming way:

• First, create a class Counter.
• Create an object counter.
• Now, Every time you call the counter object, it gets incremented by 1.

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Now, the functional programming way:

• First, we create a function Counter.
• Assign the function to a variable counter (a high order function).
• Then every time you call the counter, it gets incremented by 1.

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free variable: count
cell content:  4

This technique is known as a closure:

1. It is a function (Counter) with a nested function (increment).
2. The function returns a nested function.
3. The nested function has access to a variable not in its scope (count, a free variable).

So what makes closure special?
Well, it is simply a function capable of storing data. This approach is much cleaner than storing values in global variables.

Bonus: (similar code in Lua):