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A couple of minutes ago we talked about the fact that well, we

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might need to change our design a lot, so how we going to do

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that, that's going to be expensive. Well it's not very expensive, if we can

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do efficient refactoring. Which is another

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one of the important xp practices. And

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what does it mean to refactor? It means to take a piece of

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code who's design might be suboptimal, because for example, we evolved it, we

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didn't take into account that from the beginning some of the features that

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had to be added later, probably because we didn't even know about this

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feature, because the requirements evolved. So we're going to take this piece

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of code and we're going to restructure it, so that it becomes simple

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and maintainable. Developers are expected to

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refactor as soon as opportunities for

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improvement, are found. And that happens for example, before adding some code.

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You might look at the code that you're about to modify, or

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to which you are about to add parts, and say can we

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change the program to make the addition simple, that has maintainability or

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we can do it after adding some code to our code base.

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We might look at the code, the resulting code, and say well

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can we make the program simpler? Was the running all the tests

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and the key point here is that we don't want to refactor on

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speculation, but we want to refactor on demand, on the system, and the

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process needed. Again the goal is just to keep the code simple

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and maintainable, not to over do it. And as I mentioned before

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we're going to have a whole lesson, the next lesson on refactoring. So

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we're going to go in more depth in the discussion of this topic.