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A function is originally the idealization of how a varying quantity depends on another quantity. For example, given an input (time) you can determine an output (position of the planet) Let’s look at a simple function:. The only visible difference is we replaced the function with an object that will have the same behavior as a function. The object implementation can produce the squared value for any number input, while the object implementation will produce a function that can take in the same input and produce different outputs.