I ran across this excellent video on Emacs calc and was preparing to write about it. During my research, I discovered that I’d already written about it. That was a couple of years ago so you can consider this a reminder to watch it if you haven’t already. Calc is much much more than a simple calculator and can do some pretty astounding things. Karthik C covers only a few of them but the video does serve to show you powerful it is. For example, if it’s been a few years since you last sat in a Calculus class and you need to know the indefinite integral \(\int x^{2}e^{x}\,dx\), just power up calc, type in x^2 exp(x), press a i and discover the integral is \(x^{2}e^x+2e^{x}-2xe^{x}\). As I say, watch the video. If you want to start using calc, you should also download a copy of Sue D. Nymme’s cheat sheet. It’s, by far, the best one I know of.
Once I discovered that I’d already written about the video, I abandoned the post but started playing around with calc just for fun. It was then that I discovered something new. If you’re familiar with calc or watch the video, you know that you can get help by hitting a prefix key and ?. For example, if you can’t remember how to integrate, you can type a ? to get a list of options. However, with which-key installed, that all happens automatically. If you type a and pause before hitting another key, which-key will pop up one of its normal help buffers with all the options. That very nice and reason enough to install which-key if you’re a calc user. Actually, unless you have a photographic memory you should install which-key.