In general - developers use calculators all the time (most frequently via Google these days, but also via REPLs) so a dedicated calculator is a self-evidently u

In general - developers use calculators all the time (most frequently via Google these days, but also via REPLs) so a dedicated calculator is a self-evidently useful widget for any editor. It’s is not essential fir a new editor in 2021 but considering emacs has had Calc for some time, it is worthwhile to make improvements to widely-used legacy software. Many emacs users have used Calc in lieu of alternative “developer calculators” like Octave, the R REPL, etc, so it’s not like Calc is an extraneous feature. It’s uncommon for developers to deal with integral equations in their day-to-day work. But it’s obviously not unheard of - integral equations show up naturally in many domains of finance and engineering. I’ve had to deal with numeric integration on .NET in one of my jobs. Sometimes an exact symbolic solution is easier for the developer and the CPU than a numeric technique, so for a small handful of developers a symbolic integral calculator is a handy (if somewhat specialized) tool, and not just some bell-and-whistle.