> For example, let's say that I've got a new algorithm for calculating the cosine. Just to be safe, I add an assertion that the return value is in [-1, 1], and

> For example, let's say that I've got a new algorithm for calculating the cosine. Just to be safe, I add an assertion that the return value is in [-1, 1], and return an error if it isn't. I believe the idea here is that, if you've tested your code correctly, the assertions are never triggered and therefore your constraints are met and you don't need the checks anymore. Somewhat interestingly, the Chromium code base does something similar. There are `DCHECK` macros everywhere that are assertions that crash if the condition is false (for instance if a variable is null or some such) but they're disabled in production builds