motors API: speed_pct vs speed_dps vs speed_rps

While working on #353 #360 one thing we did not address was the API for specifying the motor speed in something other than speed_pct. The other two we want are degrees per second and rotations per second.

Some ideas that were floated:

Option 1 How about we make the default units % just like EV3-G, plus introduce scaling factor constants for those who want scientific units.

# run the motor at 50% of max speed
m.run(50)
# run the motor at 400 degrees/second
m.run(400 * m.DPS)
# run the motor at 60 RPM
m.run(60 * m.RPM)

Option 2 why not m.run(speed_pct=50), m.run(dps=400), and m.run(rpm=60)? If we define run as

def run(self, speed_pct=None, dps=None, rpm=None)

We have other parameters that need to be passed in though (speed) so basically everything becomes a positional arg. So the user would do one of

m.on_for_degrees(speed_pct=40, degrees=720)
m.on_for_degrees(speed_dps=90, degrees=720)
m.on_for_degrees(speed_rps=0.25, degrees=720)

[rhempel]

Strongly suggest you implement an EV3G compatible API as a loadable helper module - leave the basic API as is because it’s compatible across many scripting languages

[dlech]

I’ve been working on translating an EV3-G program for the last couple days and I am finding that having the API exactly the same as EV3-G is really the most useful thing to do and perhaps more importantly, it is just really fun.

What I mean by exactly is having positional arguments in the same order as the EV3-G software that take the exact same value. I thought I would like to have fancy extra features or tweak things (like changing names) to make it “better”, but I am finding that in practice, those kinds of changes are getting in the way (with the exception of correcting things that are just plain wrong in EV3-G, like using the name speed instead of power). So, I would say put this issue on the back burner and move on to something else. Once we have the basics, we can start using the library and find what we are really missing and add more if needed. By then, we should have a better idea of what feels right instead of just trying to guess like we are now.

Also…

import this