That's very cool... Some years ago I wrote my own multiple-precision arithmetic library. I implemented a lot of it in assembly so that I could access the carry

That's very cool... Some years ago I wrote my own multiple-precision arithmetic library. I implemented a lot of it in assembly so that I could access the carry bit and do full-word multiplication etc. I studied GMP and realised that my addition and subtraction were near enough perfect, but multiplication and division were far off. I now see that just because I was way off with division because I simply implemented the long division algorithm and used IDIV for words (and even that was more difficult than the other algorithms).