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fix: enable runtime usage of inverse function by using compile-time unit extraction #726

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Merged
mpusz merged 3 commits into from
Dec 21, 2025
Merged

fix: enable runtime usage of inverse function by using compile-time unit extraction #726

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507b2db
fix: enable runtime usage of inverse function by using compile-time u…
rothmichaels Sep 27, 2025
2185a13
Fix destination unit creation in `inverse`
mpusz Dec 21, 2025
4ca7dae
style: pre-commit
mpusz Dec 21, 2025
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10 changes: 6 additions & 4 deletions src/core/include/mp-units/math.h
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Original file line number Diff line number Diff line change
Expand Up @@ -413,13 +413,15 @@ template<Unit auto To, auto R, typename Rep>
}
{
#if MP_UNITS_API_NATURAL_UNITS
if constexpr (!MP_UNITS_ASSOCIATED_UNIT<MP_UNITS_REMOVE_CONST(decltype(To))>)
return (representation_values<Rep>::one() * one).force_in(To * q.unit) / q;
else
if constexpr (!MP_UNITS_ASSOCIATED_UNIT<MP_UNITS_REMOVE_CONST(decltype(To))>) {
constexpr Unit auto unit = To * quantity<R, Rep>::unit;
return (representation_values<Rep>::one() * one).force_in(unit) / q;
} else
#endif
{
constexpr QuantitySpec auto qs = get_quantity_spec(To) * quantity<R, Rep>::quantity_spec;
return qs(representation_values<Rep>::one() * one).force_in(To * q.unit) / q;
constexpr Unit auto unit = To * quantity<R, Rep>::unit;
return qs(representation_values<Rep>::one() * one).force_in(unit) / q;
}
}

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27 changes: 27 additions & 0 deletions test/runtime/math_test.cpp
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Expand Up @@ -589,4 +589,31 @@ TEST_CASE("math operations", "[math]")
REQUIRE_THAT(atan2(1. * isq::length[km], 1000. * isq::length[m]), AlmostEquals(45. * angle[deg]));
}
}

SECTION("inverse functions")
{
SECTION("inverse of time quantity returns frequency")
{
auto period = 2.0 * isq::time[s];
auto frequency = inverse<si::hertz>(period);
REQUIRE(frequency == 0.5 * isq::frequency[Hz]);
}

SECTION("inverse works with runtime values")
{
// Test the specific case that fails with consteval
double runtime_value = 3.0;
auto period = runtime_value * isq::time[s];
auto frequency = inverse<si::hertz>(period);
auto expected = (1.0 / 3.0) * isq::frequency[Hz];
REQUIRE_THAT(frequency, AlmostEquals(expected));
}

SECTION("inverse with different input units")
{
auto period_ms = 500.0 * isq::time[ms];
auto frequency = inverse<si::hertz>(period_ms);
REQUIRE(frequency == 2.0 * isq::frequency[Hz]);
}
}
}
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