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feat: common unit symbols now use EQUIV{u1, u2, ...} syntax

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Mateusz Pusz
2024-10-02 08:14:14 +02:00
parent 0d00be067a
commit 25e99fe0fa
3 changed files with 13 additions and 12 deletions
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10
docs/users_guide/framework_basics/text_output.md
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@@ -272,8 +272,8 @@ kg⋅m⋅s⁻²
Some [common units](systems_of_units.md#common-units) expressed with a specialization of the
`common_unit` class template need special printing rules for their symbols. As they represent
a minimum set of common units resulting from the addition or subtraction of multiple quantities,
we print all of them as a scaled version of the source unit. For example the following:
a minimum set of equivalent common units resulting from the addition or subtraction of multiple
quantities, we print all of them as a scaled version of the source unit. For example the following:
```cpp
std::cout << 1 * km + 1 * mi << "\n";
@@ -284,9 +284,9 @@ std::cout << 1 * km / h + 1 * m / s << "\n";
will print:
```text
40771 ([1/25146] mi = [1/15625] km)
108167 ([1/50292] mi = [1/57875] nmi)
23 ([1/5] km/h = [1/18] m/s)
40771 EQUIV{[1/25146] mi, [1/15625] km}
108167 EQUIV{[1/50292] mi, [1/57875] nmi}
23 EQUIV{[1/5] km/h, [1/18] m/s}
```
Thanks to the above, it might be easier for the user to reason about the magnitude of the resulting

7
src/core/include/mp-units/framework/unit.h
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@@ -854,18 +854,19 @@ template<typename CharT, std::output_iterator<CharT> Out, typename U, typename..
constexpr Out unit_symbol_impl(Out out, const common_unit<U, Rest...>&, const unit_symbol_formatting& fmt,
bool negative_power)
{
constexpr std::string_view separator(" = ");
constexpr std::string_view prefix("EQUIV{");
constexpr std::string_view separator(", ");
auto print_unit = [&]<Unit Arg>(Arg) {
constexpr auto u = get_common_unit_in(common_unit<U, Rest...>{}, Arg{});
unit_symbol_impl<CharT>(out, u, fmt, negative_power);
};
*out++ = '(';
detail::copy(std::begin(prefix), std::end(prefix), out);
print_unit(U{});
for_each(std::tuple<Rest...>{}, [&]<Unit Arg>(Arg) {
detail::copy(std::begin(separator), std::end(separator), out);
print_unit(Arg{});
});
*out++ = ')';
*out++ = '}';
return out;
}

8
test/static/unit_symbol_test.cpp
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@@ -117,12 +117,12 @@ static_assert(unit_symbol<unit_symbol_formatting{.encoding = ascii}>(mag<60> * s
static_assert(unit_symbol(mag_ratio<1, 18> * metre / second) == "[1/18] m/s");
// common units
static_assert(unit_symbol(get_common_unit(kilo<metre>, mile)) == "([1/25146] mi = [1/15625] km)");
static_assert(unit_symbol(get_common_unit(kilo<metre> / hour, metre / second)) == "([1/5] km/h = [1/18] m/s)");
static_assert(unit_symbol(get_common_unit(kilo<metre>, mile)) == "EQUIV{[1/25146] mi, [1/15625] km}");
static_assert(unit_symbol(get_common_unit(kilo<metre> / hour, metre / second)) == "EQUIV{[1/5] km/h, [1/18] m/s}");
static_assert(unit_symbol(get_common_unit(kilo<metre> / hour, metre / second) / second) ==
"([1/5] km/h = [1/18] m/s)/s");
"EQUIV{[1/5] km/h, [1/18] m/s}/s");
static_assert(unit_symbol(get_common_unit(kilo<metre> / hour, metre / second) * second) ==
"([1/5] km/h = [1/18] m/s) s");
"EQUIV{[1/5] km/h, [1/18] m/s} s");
// derived units
static_assert(unit_symbol(one) == ""); // NOLINT(readability-container-size-empty)