Optimize text output for scaled units

[mpusz]

Parenthesis for scaled units is needed only when more than one unit is used in the symbol of a derived unit. Otherwise, such grouping is not necessary. To make it clear where the runtime part of the quantity ends and the compile time unit symbol begins, an x separator can be used.

[chiphogg]

Could you give a simple example to illustrate? I think the issue would read a lot better with an example.

[mpusz]

Sure! Sorry, I should've done it right away, but due to the lack of time, I just made a short note for myself.

Here are some examples:

std::cout << 10 * (mag<100> * km) << "\n";
std::court << (10 * (mag<100> * km)).unit << "\n";
std::cout << 10 * (mag_ratio<1, 18000> * (m/s)) << "\n";
std::cout << 10 * (mag_ratio<1, 18000> * m/s) << "\n";
std::cout << 10 * km/h + 5 * m/s << "\n";
std::cout << 10 * L_per_100km << "\n";

Now:

10 (100 km)
(100 km)
10 (1/18 × 10⁻³ m/s)
10 (1/18 × 10⁻³ m)/s
140 EQUIV{(1/5 km/h), (1/18 m/s)}
10 L/(100 km)

Better:

10 × 100 km
100 km
10 × 1/18 × 10⁻³ m/s
10 (1/18 × 10⁻³ m)/s
140 EQUIV{1/5 km/h, 1/18 m/s}
10 L/(100 km)

To summarize:

• if the unit of a quantity is a scaled_unit we do not put (...) (we do it if a scaled unit is a part of a derived_unit being printed)
• if we print the entire quantity (and not just a unit), then we add × in between the unit and a number
• additionally, we could consider if line 4 should not result with 10 × 1/18 × 10⁻³ m/s, but this requires even more logic and optimizations.

Please let me know your thoughts.

[chiphogg]

Personally, I'm partial to square brackets, and I'm partial to always having them be present.

I think 10 × 1/18 × 10⁻³ m/s looks a little strange, and 10 (1/18 × 10⁻³ m/s) just seems better to me.

Admittedly, 140 EQUIV{1/5 km/h, 1/18 m/s} is less cluttered than 140 EQUIV{(1/5 km/h), (1/18 m/s)}, which is nice.

As for the optimizations you mention, I think this would boil down to gathering all numeric scale factors into a single common one. In Au at least, this was really easy to get working locally, but I haven't put it out for review because I'm not sure I like the implications. Some seem clearly better, while others are a little bit worse --- for example, we'd lose the ability to have L / [100 km].

[Spammed]

In my humble opinion: a) If square brackets are used, they should cover the entire unit. b) Whether with or without square brackets should be a formatting option. For example: 10 L/[100 km] looks wrong to me and 10 [L/100 km] misses the point. So 10 L/(100 km) or 10 [L/(100 km)].

[mpusz]

LEWGI's feedback was that we already have too many formatting options. They continue to describe this as a debug text output, and for debugging, we do not have to support everything. They already suggested removing some of the options, but I have provided some pushback so far.

[chiphogg]

Same for me my friend :/

Sorry, what was the same for you? I didn't understand what you were referring to.