> Most libraries only support static checking of units (AFAIK).

I found that to be the case. Indeed, if would be nice to integrate

both approaches elegantly. I haven't figured out how yet.

> (try to type "(1m + 1ft + 2 yards + 50in) * 5 / (8 km/h) in minutes"

> for instance).

I had to try it using quantities :)

>>> fromString "(1m + 1ft + 2 yard + 50in) * 5 / (8 km/h) => minute"

Right 0.16513500000000006 minute