forked from mpusz/mp-units
89 lines
3.1 KiB
ReStructuredText
89 lines
3.1 KiB
ReStructuredText
Quick Start
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===========
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Here is a small example of possible operations::
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#include <units/isq/si/area.h>
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#include <units/isq/si/frequency.h>
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#include <units/isq/si/length.h>
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#include <units/isq/si/speed.h>
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#include <units/isq/si/time.h>
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using namespace units::isq::si::references;
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// simple numeric operations
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static_assert(10 * km / 2 == 5 * km);
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// unit conversions
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static_assert(1 * h == 3600 * s);
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static_assert(1 * km + 1 * m == 1001 * m);
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// dimension conversions
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inline constexpr auto kmph = km / h;
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static_assert(1 * km / (1 * s) == 1000 * (m / s));
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static_assert(2 * kmph * (2 * h) == 4 * km);
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static_assert(2 * km / (2 * kmph) == 1 * h);
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static_assert(2 * m * (3 * m) == 6 * m2);
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static_assert(10 * km / (5 * km) == 2);
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static_assert(1000 / (1 * s) == 1 * kHz);
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.. admonition:: Try it on Compiler Explorer
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`Example #1 <https://godbolt.org/z/5dvY8Woh1>`_
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This library requires some C++20 features (concepts, classes as
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:abbr:`NTTP (Non-Type Template Parameter)`, ...). Thanks to them the user gets a powerful
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but still easy to use interface where all unit conversions and dimensional analysis can be
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performed without sacrificing on accuracy. Please see the below example for a quick preview
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of basic library features::
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#include <units/format.h>
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#include <units/isq/si/international/length.h>
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#include <units/isq/si/international/speed.h>
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#include <units/isq/si/length.h>
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#include <units/isq/si/speed.h>
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#include <units/isq/si/time.h>
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#include <units/quantity_io.h>
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#include <iostream>
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using namespace units::isq;
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constexpr Speed auto avg_speed(Length auto d, Time auto t)
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{
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return d / t;
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}
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int main()
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{
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using namespace units::isq::si::literals;
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using namespace units::isq::si::references;
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using namespace units::aliases::isq::si::international;
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constexpr Speed auto v1 = 110 * (km / h);
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constexpr Speed auto v2 = mi_per_h(70.);
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constexpr Speed auto v3 = avg_speed(220_q_km, 2_q_h);
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constexpr Speed auto v4 = avg_speed(si::length<si::international::mile>(140), si::time<si::hour>(2));
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constexpr Speed auto v5 = quantity_cast<si::speed<si::metre_per_second>>(v3);
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constexpr Speed auto v6 = quantity_cast<si::metre_per_second>(v4);
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constexpr Speed auto v7 = quantity_cast<int>(v6);
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std::cout << v1 << '\n'; // 110 km/h
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std::cout << v2 << '\n'; // 70 mi/h
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std::cout << std::format("{}", v3) << '\n'; // 110 km/h
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std::cout << std::format("{:*^14}", v4) << '\n'; // ***70 mi/h****
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std::cout << std::format("{:%Q in %q}", v5) << '\n'; // 30.5556 in m/s
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std::cout << std::format("{0:%Q} in {0:%q}", v6) << '\n'; // 31.2928 in m/s
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std::cout << std::format("{:%Q}", v7) << '\n'; // 31
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}
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.. admonition:: Try it on Compiler Explorer
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`Example #2 <https://godbolt.org/z/bcb87Kvea>`_
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.. seealso::
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You can find more code examples in the :ref:`examples:Examples` chapter.
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