If you use Emacs, then perhaps surprisingly one of the best places to hang out is the Google+ Emacs community.

You also may or may not be aware of the
calc
facility embedded in Emacs. It seems to be one of the lesser-known
features, and even among those who do know about it, many are unaware
how sophisticated it is. You can invoke it with `M-x calc`

, or ```
C-x *
*
```

and at first glance it seems quite primitive… until you read the
manual, at which point it can instead seem impenetrable!

Hidden underneath the spartan, stack-based interface is matrix and vector arithmetic, date and time calculations, unit-aware calculations and conversion, symbolic manipulation, and on it goes.

Nearly a year ago Andrew Hyatt posted a series of tutorials that explored a lot of the corners, but one of the weaknesses of Google+ is that content can be hard to aggregate or find again.

So, when I remembered the other day I went back and dug up all the ones I could find, in order to provide a pointer back to them! Just as I was completing the list I discovered that there is already one archive on the EmacsWiki, but one more is certainly not going to hurt discoverability.

- Hex-decimal conversion (and general base conversion)
- How old is David Hasselhoff? Basic date calculations. Also, toggle digit grouping (number formatting)
- More date-time manipulation In particular, Unix epoch conversion.
- Random numbers
- Unit conversion, including defining custom units.
- Pi and digit precision
- String to binary conversion
- Exact fractional arithmetic
- Algebreic manipulation
- More algebra
- Finance
- Calculus (Integrals and derivatives)
- Bit manipulation