Step Function

I think thatБЂ™s a fruitful way to think about it. Seibel: How about stepping through code in a debugger? Is that something youБЂ™ll do if all else fails? Steele: It depends on the length of the program. And of course you can have tools that will help you to skip sections you donБЂ™t need to step through because youБЂ™re confident that those parts are OK. And of course Common Lisp has this very nice STEP function, which is very helpful. IБЂ™ve stepped through a lot of Common Lisp code. The ability to skip over particular subroutines whose details you trust, of course, buys you a lot. Also the ability to set traps and say, БЂњI really donБЂ™t need to look at this until this particular loop has gone around for the seventeenth time.БЂ«And there were hardware tools to support that on the PDP-10, which was nice, at least at MIT. They tended to modify their machines in those days, to add features. And thereБЂ™s a lot to be said for watching the actual execution of code in various ways. Seibel: Do you ever try to formally prove your code correct? Steele: Well, it depends on the code ...»