magnum/src/Magnum/Math/Angle.h

#ifndef Magnum_Math_Angle_h
#define Magnum_Math_Angle_h
/*
    This file is part of Magnum.

    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
                2020, 2021, 2022 Vladimír Vondruš <mosra@centrum.cz>

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/

/** @file
 * @brief Class @ref Magnum::Math::Deg, @ref Magnum::Math::Rad, literal @link Magnum::Math::Literals::operator""_degf() @endlink, @link Magnum::Math::Literals::operator""_radf() @endlink, @link Magnum::Math::Literals::operator""_deg() @endlink, @link Magnum::Math::Literals::operator""_rad() @endlink
 */

#ifndef CORRADE_NO_DEBUG
#include <Corrade/Utility/Debug.h>
#endif

#include "Magnum/visibility.h"
#include "Magnum/Math/Constants.h"
#include "Magnum/Math/Math.h"
#include "Magnum/Math/Unit.h"

namespace Magnum { namespace Math {

/**
@brief Angle in degrees

Along with @ref Rad provides convenience classes to make angle specification
and conversion less error-prone.

@section Math-Deg-usage Usage

You can enter the value either by using a literal:

@snippet MagnumMath.cpp Deg-usage

Or explicitly convert a unitless value (such as output from some function) to
either degrees or radians:

@snippet MagnumMath.cpp Deg-usage-convert

The classes support all arithmetic operations, such as addition, subtraction
or multiplication/division by a unitless number:

@snippet MagnumMath.cpp Deg-usage-operations

It is also possible to compare angles with all comparison operators, but
comparison of degrees and radians is not possible without explicit conversion
to common type:

@snippet MagnumMath.cpp Deg-usage-comparison

It is possible to seamlessly convert between degrees and radians and explicitly
convert the value back to the underlying type:

@snippet MagnumMath.cpp Deg-usage-conversion

@section Math-Angle-explicit-conversion Requirement of explicit conversion

The requirement of explicit conversions from and to unitless types helps to
reduce unit-based errors. Consider the following example that would compile
only if implicit conversions were allowed:

@code{.cpp}
namespace std { float sin(float angle); }
Float sine(Rad angle);

Float a = 60.0f;                // degrees
sine(a);                        // silent error, sine() expected radians

auto b = 60.0_degf;             // degrees
std::sin(b);                    // silent error, std::sin() expected radians
@endcode

These silent errors are easily avoided by requiring explicit conversions:

@snippet MagnumMath.cpp Deg-usage-explicit-conversion

@see @ref Magnum::Deg, @ref Magnum::Degh, @ref Magnum::Degd
*/
template<class T> class Deg: public Unit<Deg, T> {
    public:
        /**
         * @brief Default constructor
         *
         * Equivalent to @ref Deg(ZeroInitT).
         */
        /* Needs to be Math::Deg here and in all other places because older
           Clang and both MSVC 2015 and 2017 treat it as a template instantce
           Deg<T> instead of a Deg template */
        constexpr /*implicit*/ Deg() noexcept: Unit<Math::Deg, T>{ZeroInit} {}

        /** @brief Construct a zero angle */
        constexpr explicit Deg(ZeroInitT) noexcept: Unit<Math::Deg, T>{ZeroInit} {}

        /** @brief Construct without initializing the contents */
        explicit Deg(Magnum::NoInitT) noexcept: Unit<Math::Deg, T>{Magnum::NoInit} {}

        /** @brief Explicit constructor from unitless type */
        constexpr explicit Deg(T value) noexcept: Unit<Math::Deg, T>(value) {}

        /** @brief Construct from another underlying type */
        template<class U> constexpr explicit Deg(Unit<Math::Deg, U> value) noexcept: Unit<Math::Deg, T>(value) {}

        /** @brief Copy constructor */
        constexpr /*implicit*/ Deg(Unit<Math::Deg, T> other) noexcept: Unit<Math::Deg, T>(other) {}

        /**
         * @brief Construct degrees from radians
         *
         * Performs conversion from radians to degrees, i.e.: @f[
         *      deg = rad \frac{180}{\pi}
         * @f]
         * @m_keyword{degrees(),GLSL degrees(),}
         */
        constexpr /*implicit*/ Deg(Unit<Rad, T> value);
};

namespace Literals {

/** @relatesalso Magnum::Math::Deg
@brief Double-precision degree value literal

Example usage:

@snippet MagnumMath.cpp _deg

@see @link operator""_degf() @endlink, @link operator""_rad() @endlink
@m_keywords{_deg deg}
*/
constexpr Deg<Double> operator "" _deg(long double value) { return Deg<Double>(Double(value)); }

/** @relatesalso Magnum::Math::Deg
@brief Single-precision degree value literal

Example usage:

@snippet MagnumMath.cpp _degf

@see @link operator""_deg() @endlink, @link operator""_radf() @endlink
@m_keywords{_degf degf}
*/
constexpr Deg<Float> operator "" _degf(long double value) { return Deg<Float>(Float(value)); }

}

/**
@brief Angle in radians

See @ref Deg for more information.
@see @ref Magnum::Rad, @ref Magnum::Radh, @ref Magnum::Radd
*/
template<class T> class Rad: public Unit<Rad, T> {
    public:
        /**
         * @brief Default constructor
         *
         * Equivalent to @ref Rad(ZeroInitT).
         */
        constexpr /*implicit*/ Rad() noexcept: Unit<Math::Rad, T>{ZeroInit} {}

        /** @brief Constructor a zero angle */
        constexpr explicit Rad(ZeroInitT) noexcept: Unit<Math::Rad, T>{ZeroInit} {}

        /** @brief Construct without initializing the contents */
        explicit Rad(Magnum::NoInitT) noexcept: Unit<Math::Rad, T>{Magnum::NoInit} {}

        /** @brief Construct from unitless type */
        constexpr explicit Rad(T value) noexcept: Unit<Math::Rad, T>(value) {}

        /** @brief Construct from another underlying type */
        template<class U> constexpr explicit Rad(Unit<Math::Rad, U> value) noexcept: Unit<Math::Rad, T>(value) {}

        /** @brief Copy constructor */
        constexpr /*implicit*/ Rad(Unit<Math::Rad, T> value) noexcept: Unit<Math::Rad, T>(value) {}

        /**
         * @brief Construct radians from degrees
         *
         * Performs conversion from degrees to radians, i.e.: @f[
         *      rad = deg \frac{\pi}{180}
         * @f]
         * @m_keyword{radians(),GLSL radians(),}
         */
        constexpr /*implicit*/ Rad(Unit<Deg, T> value);
};

namespace Literals {

/** @relatesalso Magnum::Math::Rad
@brief Double-precision radian value literal

See @link operator""_deg() @endlink for more information.
@see @link operator""_radf() @endlink
@m_keywords{_rad rad}
*/
constexpr Rad<Double> operator "" _rad(long double value) { return Rad<Double>(Double(value)); }

/** @relatesalso Magnum::Math::Rad
@brief Single-precision radian value literal

See @link operator""_degf() @endlink for more information.
@see @link operator""_rad() @endlink
@m_keywords{_radf radf}
*/
constexpr Rad<Float> operator "" _radf(long double value) { return Rad<Float>(Float(value)); }

}

template<class T> constexpr Deg<T>::Deg(Unit<Rad, T> value): Unit<Math::Deg, T>(T(180)*T(value)/Math::Constants<T>::pi()) {}
template<class T> constexpr Rad<T>::Rad(Unit<Deg, T> value): Unit<Math::Rad, T>(T(value)*Math::Constants<T>::pi()/T(180)) {}

#ifndef CORRADE_NO_DEBUG
/** @debugoperator{Rad} */
template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Unit<Rad, T>& value) {
    return debug << "Rad(" << Corrade::Utility::Debug::nospace << T(value) << Corrade::Utility::Debug::nospace << ")";
}

/** @debugoperator{Deg} */
template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& debug, const Unit<Deg, T>& value) {
    return debug << "Deg(" << Corrade::Utility::Debug::nospace << T(value) << Corrade::Utility::Debug::nospace << ")";
}

/* Explicit instantiation for commonly used types */
#ifndef DOXYGEN_GENERATING_OUTPUT
extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Float>&);
extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Float>&);
extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Rad, Double>&);
extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Unit<Deg, Double>&);
#endif
#endif

}}

namespace Corrade { namespace Utility {

#if !defined(CORRADE_NO_TWEAKABLE) && (defined(DOXYGEN_GENERATING_OUTPUT) || defined(CORRADE_TARGET_UNIX) || (defined(CORRADE_TARGET_WINDOWS) && !defined(CORRADE_TARGET_WINDOWS_RT)) || defined(CORRADE_TARGET_EMSCRIPTEN))
/**
@tweakableliteral{Magnum::Math::Deg}

Parses the @link Magnum::Math::Literals::operator""_degf @endlink literal.
@experimental
*/
template<> struct MAGNUM_EXPORT TweakableParser<Magnum::Math::Deg<Magnum::Float>> {
    TweakableParser() = delete;

    /** @brief Parse the value */
    static std::pair<TweakableState, Magnum::Math::Deg<Magnum::Float>> parse(Containers::StringView value);
};

/**
@tweakableliteral{Magnum::Math::Deg}

Parses the @link Magnum::Math::Literals::operator""_deg @endlink literal.
@experimental
*/
template<> struct MAGNUM_EXPORT TweakableParser<Magnum::Math::Deg<Magnum::Double>> {
    TweakableParser() = delete;

    /** @brief Parse the value */
    static std::pair<TweakableState, Magnum::Math::Deg<Magnum::Double>> parse(Containers::StringView value);
};

/**
@tweakableliteral{Magnum::Math::Rad}

Parses the @link Magnum::Math::Literals::operator""_radf @endlink literal.
@experimental
*/
template<> struct MAGNUM_EXPORT TweakableParser<Magnum::Math::Rad<Magnum::Float>> {
    TweakableParser() = delete;

    /** @brief Parse the value */
    static std::pair<TweakableState, Magnum::Math::Rad<Magnum::Float>> parse(Containers::StringView value);
};

/**
@tweakableliteral{Magnum::Math::Rad}

Parses the @link Magnum::Math::Literals::operator""_rad @endlink literal.
@experimental
*/
template<> struct MAGNUM_EXPORT TweakableParser<Magnum::Math::Rad<Magnum::Double>> {
    TweakableParser() = delete;

    /** @brief Parse the value */
    static std::pair<TweakableState, Magnum::Math::Rad<Magnum::Double>> parse(Containers::StringView value);
};
#endif

}}

#endif