My experience using this library

[mathisloge]

I’ve been looking for a small side project to try out this library, and I’m really excited!

Using this library has given me so much more confidence when working with different units. It’s already saved me several times, especially when displaying units in a Qt UI — formatting units to the desired UI representation is now just a one-liner!

Great work on this project! I’m really looking forward to seeing it become part of the standard someday.

For anyone interested, here’s what I’ve been working on:
https://github.com/mathisloge/cocktail-maker/

Here’s how I’ve used the library:

• Created a custom unit for raw readings from the HX711 sensor and converted those to grams
• Defined a custom unit for the steps of a stepper motor, combined with velocity and acceleration
• Represented all liquids in liters, and used step velocity and flow rate to calculate the time required to run the stepper motor
• Managed booster liquids with percentages
• Convert units with fmt formatting to display them in the UI

Really fantastic work — thanks so much for creating this!

[mpusz]

Thank you for your kind words! It really matters a lot to us.

[mpusz]

I took a quick look at your project and have a few questions and comments.

[mpusz]

I love your use case (https://github.com/mathisloge/cocktail-maker/blob/d03eeff639fba4adc4e91b70a06afb05320eda9b/ui/app/main.cpp). I never thought my library would be helping a bartender to make drinks 🤣

[mathisloge]

Oh didn't expect a review but your comments are totally right - thanks!! :)

I never thought my library would be helping a bartender to make drinks 🤣

Hopefully I won't have to make them myself at the next party 🤣

[mpusz]

Why do you need that and why is there no value assigned?

https://github.com/mathisloge/cocktail-maker/blob/d03eeff639fba4adc4e91b70a06afb05320eda9b/src/include/cm/units.hpp#L19

Typically, users should not have a need to decltype our types. I would like to understand your rationale here. Isn't the below better:

inline constexpr auto gram_per_litre = si::gram / si::litre;

[mpusz]

https://github.com/mathisloge/cocktail-maker/blob/d03eeff639fba4adc4e91b70a06afb05320eda9b/src/include/cm/units.hpp#L27-L28

The second line should probably look like:

using StepsPerSecondSq = quantity<step / square(si::second)>;

The fact that we can divide a quantity by a unit is unfortunate and should probably not be done on purpose like above.

[mpusz]

https://github.com/mathisloge/cocktail-maker/blob/d03eeff639fba4adc4e91b70a06afb05320eda9b/src/include/cm/hw/hx711_sensor.hpp#L19-L21

Why is this unit defined as dimensionless? Isn't it a unit of mass?