A Philosophy of Software Design

by John Ousterhout

A different opinion: Clean Code In the book Clean Code1, Robert Martin argues that functions should be broken up based on length alone. He says that functions should be extremely short, and that even 10 lines is too long: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that.... Blocks within if statements, else statements, while statements, and so on should be one line long. Probably that line should be a function call.... This also implies that functions should not be large enough to hold nested structures. Therefore, the indent level of a function should not be greater than one or two. This, of course, makes the functions easier to read and understand. I agree that shorter functions are generally easier to understand than longer ones. However, once a function gets down to a few dozen lines, further reductions in size are unlikely to have much impact on readability. A more important issue is: does breaking up a function reduce the overall complexity of the system? In other words, is it easier to read several short functions and understand how they work together than it is to read one larger function? More functions means more interfaces to document and learn. If functions are made too small, they lose their independence, resulting in conjoined functions that must be read and understood together. When this happens, then it’s better to keep the larger function, so all of the related code is one place...