RFC: Units of measurement for D (Phobos?)

[Michael]

> enum radian = meter / meter; // ditto
> enum steradian = square(meter) / square(meter); /// ditto
>
> What on earth does this mean?

It has to do with the definition of radian itself. If you draw a 
circle (of any radius) around an angle. The measure of the angle 
is radian is the ratio between the arc length of the circle and 
the radius. This is the reason why one full rotation is 2*pi 
radians: A circle's circumference is always 2*pi times its radius.

Steradian is similar, but in three dimensions.