Explicit explanation of how to unwrap values (eg for serialization)

[spease]

There's a value_unsafe parameter, but it's unclear to me if that's the "right" way to do things if you just want to extract the value (sans the units). It'd be nice if this were explicitly stated somewhere, too, so that new users can discover it without asking.

Thanks!

[adeschamps]

In this situation, I explicitly divide by what I expect the units to be. That should give you a dimensionless value. Then you can use the value() method from the Dimensionless trait. Note that value() returns a reference, so you'll have to dereference it as well:

fn send_speed_command(speed: si::MeterPerSecond<f64>) {
    let command = ApiCommand {
        speed_mps: *(speed / si::MPS).value(),
    };
    send(command);
}

[wellcaffeinated]

Just curious... why is there a specific type for dimensionless values? I would expect this to work instead:

let x :f64 = speed / si::MPS;

Also, i'd expect to be able to use an .into if there's a good reason for a unitless type

let x :f64 = (speed / si::MPS).into();

[droundy]

I think a dimensionless your is valuable because when you've got an f64 it may or may not actually hold a dimensional value, e.g. a distance a user provided. If an f64 were treated as dimensionless then it would be very hard to audit a coffee to ensure that all dimensions are correct.