Add utilities to forward declare compound units #342
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The mechanism may be a little bit complicated, but I think it's manageable. It's also necessary in order to get forward declaration files working in Aurora's monorepo, which was what I used to design the feature. The fact that we're now able to do so gives me confidence that Au's forward declarations now have everything they need to be useful and usable in the real world. I also added a how-to doc explaining how to use the forward declaration feature generally. Fixes #232.
chiphogg
added
release notes: ✨ lib (enhancement)
geoffviola
approved these changes
Dec 6, 2024
| practices](./new-units.md#alias-vs-strong) for new units suggests using a simple _alias_ in this | ||
| case, rather than a strong type (for example, `UnitQuotientT<Meters, Seconds>`). However, this | ||
| cannot be computed without the full machinery of the library, which can cost tens of milliseconds. | ||
| This may not sound like much, but it's far too slow for a forward declaration file. |
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Nit: Can we quantify what is the too slow and what is the target?
| using KilometersPerHourFwd = au::ForwardDeclareUnitProduct<au::Kilo<au::Meters>, InverseHours>; | ||
| using KilometersPerHour = typename KilometersPerHourFwd::unit_type; | ||
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| std::string print_to_string(const au::QuantityD<KilometersPerHour>& speed); |
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Comment: I was hoping that the fwd types would be named the same as the underlying types. But I guess that wouldn't have the checks that we care about.
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Yep, this was the cleanest way I could think of to make it easy to check the answers robustly.
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The mechanism may be a little bit complicated, but I think it's
manageable. It's also necessary in order to get forward declaration
files working in Aurora's monorepo, which was what I used to design the
feature. The fact that we're now able to do so gives me confidence that
Au's forward declarations now have everything they need to be useful and
usable in the real world.
I also added a how-to doc explaining how to use the forward declaration
feature generally.
Fixes #232.