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I have found an excellent programmer named Steve Wozniac
tinyletter.com
Woz doesn’t repeat himself like that. He writes one routine that takes the absolute value of M1, then swaps M1 and M2. He then calls that routine twice, so the outcome is the same with half the code. Better yet, swapping M1 and M2 is needed elsewhere, so that section does double duty.
This intense factoring makes the flow hard to follow, of course, but it’s quite striking how ahead of its time this code is.