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Domain, Range, And Codomain

Kevin Sookocheff explains the concepts of domain, range, and codomain:

That is, a function relates an input to an output. But, not all input values have to work, and not all output values. For example, you can imagine a function that only works for positive numbers, or a function that only returns natural numbers. To more clearly specify the types and values of a functions input and output, we use the terms domain, range, and codomain.

Speaking as simply as possible, we can define what can go into a function, and what can come out:

  • domain: what can go into a function

  • codomain: what may possibly come out of a function

  • range: what actually comes out of a function

Read on for more, including a couple of examples.  These are important concepts for learning functional programming.