Add Eigen kinematics example - #737
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This shows off a nice simplification of some Eigen code. We get good mileage out of automatic unit conversions, and even the gravity constant. Along the way, we tweak the naming and ordering in the index file, to be more consistent with the titles that show up in the sidebar.
chiphogg
marked this pull request as ready for review
August 24, 2026 20:10
hoffbrinkle
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Aug 24, 2026
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| Au's Eigen support makes it easier to get your units right _robustly_, and often makes your code | ||
| easier to read. Lifetime safety is the one thing it leaves exactly as it found it, for better and | ||
| for worse, so make sure you're familiar with the Eigen [safety guide] before you start using Au with |
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Just out of curiosity, I was curious what kind of documentation Eigen had for all this. Mostly because I was thinking this could be simplified to "before you start using Eigen" (because Au doesn't add anything).
Having checked it out, we should leave it as you wrote it. The Eigen stuff is a little more scary ("don't use auto unless you are 100% sure)...
| const Velocity &v, | ||
| const Acceleration &a, | ||
| QuantityD<Seconds> dt) { | ||
| return x + v * dt + 0.5 * a * dt * dt; |
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Do you want to use int_pow here?
Suggested change
| return x + v * dt + 0.5 * a * dt * dt; | |
| return x + v * dt + 0.5 * a * int_pow<2>(dt); |
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This shows off a nice simplification of some Eigen code. We get good
mileage out of automatic unit conversions, and even the gravity
constant.
Along the way, we tweak the naming and ordering in the index file, to be
more consistent with the titles that show up in the sidebar.