For each Magnitude `m`, we now support:
- `is_rational(m)` tells whether it represents a rational number.
- `is_integral(m)` tells whether it represents an integer (and
`is_integral(m)` implies `is_rational(m)`).
- `m.value<T>` represents the value of `m` in the type `T`.
If `T` is integral, we only support `m.value<T>` when `is_integral(m)`.
We also perform all intermediate computations in the widest type of the
same category (floating point, signed, or unsigned). This means we can,
for example, give first-class support to embedded users who may have
hardware support only for `float`: we can ensure they get the most
accurate `float` value we can compute, without burdening them with a
dependency on `long double` in their runtime code.
We are not yet ready to replace `ratio` as the definition of unit
magnitudes, but we're a step closer. The next step will be to decompose
a Magnitude into numerator, denominator, and irrational parts, giving us
full bidirectional convertibility with existing `ratio` instances. Then
we can migrate over in a controlled fashion.
Chip Hogg
a6b6afe438