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Gforth Manual

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3.13 Factoring

If you try to write longer definitions, you will soon find it hard to keep track of the stack contents. Therefore, good Forth programmers tend to write only short definitions (e.g., three lines). The art of finding meaningful short definitions is known as factoring (as in factoring polynomials).

Well-factored programs offer additional advantages: smaller, more general words, are easier to test and debug and can be reused more and better than larger, specialized words.

So, if you run into difficulties with stack management, when writing code, try to define meaningful factors for the word, and define the word in terms of those. Even if a factor contains only two words, it is often helpful.

Good factoring is not easy, and it takes some practice to get the knack for it; but even experienced Forth programmers often don't find the right solution right away, but only when rewriting the program. So, if you don't come up with a good solution immediately, keep trying, don't despair.

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