What This Buys You in Practice
Last timeProving It for Every Number
A loop is correct after any number of passes for the same reason a ladder argument works. Writing down what stays true on every pass is the working form of the whole course.
The previous lesson proved a claim with one case per whole number using two
checks. A loop runs some number of times and has to be right after each of
them, which is a claim with one case per pass.
Same shape, same method, and this time the method earns its keep, because the
result is a way of knowing a loop is correct without running it on every input.
The lesson stops here
1 more paragraph to go
You have read the opening. The rest of the argument, the problems that check whether it landed, and the lines worth keeping at the end all come with a plan.
The first lesson of every course in the library reads the whole way through, free, so you can see exactly what the rest of them are.
See the planThe contentsThis is the reading half
Starting the course gives you your own copy of it. Every idea on every page has problems standing under it, marked with a reason rather than a tick, and any sentence you do not believe can be opened and argued with. None of that can happen on a page nobody owns.
The contents