cachingdms.h

/*
    SPDX-FileCopyrightText: 2016 Akarsh Simha <akarsh.simha@kdemail.net>
 
    SPDX-License-Identifier: GPL-2.0-or-later
*/
 
#pragma once
 
#include "dms.h"
 
/**
 * @class CachingDms
 * @short a dms subclass that caches its sine and cosine values every time the angle is changed.
 * @note This is to be used for those angles where sin/cos is repeatedly computed.
 * @author Akarsh Simha <akarsh@kde.org>
 */
 
class CachingDms : public dms
{
  public:
    /**
     * @short Default Constructor
     */
    CachingDms() : dms(), m_sin(NaN::d), m_cos(NaN::d)
    {
#ifdef COUNT_DMS_SINCOS_CALLS
        m_cacheUsed = true;
        ++cachingdms_constructor_calls;
#endif
    };
 
    /**
     * @short Degree angle constructor
     * @param x is the angle in degrees
     */
    explicit CachingDms(const double &x);
 
    /**
     * @short QString constructor
     */
    explicit CachingDms(const QString &s, bool isDeg = true);
 
    /**
     * @short DMS representation constructor
     */
    explicit CachingDms(const int &d, const int &m = 0, const int &s = 0, const int &ms = 0);
 
#ifdef COUNT_DMS_SINCOS_CALLS
    /**
     * @short Destructor must count bad cache uses
     */
    ~CachingDms();
#endif
 
    /**
     * @short Sets the angle in degrees supplied as a double
     * @note Re-implements dms::setD() with sine/cosine caching
     */
    inline void setD(const double &x) override
    {
        dms::setD(x);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
        if (!m_cacheUsed)
            ++cachingdms_bad_uses;
        m_cacheUsed = false;
#endif
    }
 
    /**
     * @short Overrides dms::setD()
     */
    inline void setD(const int &d, const int &m, const int &s, const int &ms = 0) override
    {
        dms::setD(d, m, s, ms);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
        if (!m_cacheUsed)
            ++cachingdms_bad_uses;
        m_cacheUsed = false;
#endif
    }
 
    /**
     * @short Sets the angle in hours, supplied as a double
     * @note Re-implements dms::setH() with sine/cosine caching
     * @note While this and other methods internally call setD, we want to avoid unnecessary vtable lookups. We'd rather have inline than virtual when speed matters in general.
     */
    inline void setH(const double &x) override
    {
        dms::setH(x);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
        if (!m_cacheUsed)
            ++cachingdms_bad_uses;
        m_cacheUsed = false;
#endif
    }
 
    /**
     * @short Sets the angle in HMS form
     * @note Re-implements dms::setH() with sine/cosine caching
     */
    inline void setH(const int &h, const int &m, const int &s, const int &ms = 0) override
    {
        dms::setH(h, m, s, ms);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
#endif
    }
 
    /**
     * @short Sets the angle from string
     * @note Re-implements dms::setFromString()
     */
    inline bool setFromString(const QString &s, bool isDeg = true) override
    {
        bool retval = dms::setFromString(s, isDeg);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
        if (!m_cacheUsed)
            ++cachingdms_bad_uses;
        m_cacheUsed = false;
#endif
        return retval;
    }
 
    /**
     * @short Sets the angle in radians
     */
    inline void setRadians(const double &a) override
    {
        dms::setRadians(a);
        dms::SinCos(m_sin, m_cos);
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta -= 2;
        if (!m_cacheUsed)
            ++cachingdms_bad_uses;
        m_cacheUsed = false;
#endif
    }
 
    /**
     * @short Sets the angle using atan2()
     * @note The advantage is that we can calculate sin/cos faster because we know the tangent
     */
    void setUsing_atan2(const double &y, const double &x);
 
    /**
     * @short Sets the angle using asin()
     * @param sine Sine of the angle
     * @note The advantage is that we can cache the sine value supplied
     * @note The limited range of asin must be borne in mind
     */
    void setUsing_asin(const double &sine);
 
    /**
     * @short Sets the angle using acos()
     * @param cosine Cosine of the angle
     * @note The advantage is that we can cache the cosine value supplied
     * @note The limited range of acos must be borne in mind
     */
    void setUsing_acos(const double &cosine);
 
    /**
     * @short Get the sine and cosine together
     * @note Re-implements dms::SinCos()
     * @note This just uses the cached values assuming that they are good
     */
    inline void SinCos(double &s, double &c) const
    {
        s = m_sin;
        c = m_cos;
#ifdef COUNT_DMS_SINCOS_CALLS
        cachingdms_delta += 2;
        m_cacheUsed = true;
#endif
    }
 
    /**
     * @short Get the sine of this angle
     * @note Re-implements dms::sin()
     * @note This just uses the cached value assuming that it is good
     */
    inline double sin() const
    {
#ifdef COUNT_DMS_SINCOS_CALLS
        ++cachingdms_delta;
        m_cacheUsed = true;
#endif
        return m_sin;
    }
 
    /**
     * @short Get the cosine of this angle
     * @note Re-implements dms::cos()
     * @note This just uses the cached value assuming that it is good
     */
    inline double cos() const
    {
#ifdef COUNT_DMS_SINCOS_CALLS
        ++cachingdms_delta;
        m_cacheUsed = true;
#endif
        return m_cos;
    }
 
    /**
     * @short Construct an angle from the given string
     * @note Re-implements dms::fromString()
     */
    static CachingDms fromString(const QString &s, bool deg);
 
    /**
     * @short operator -
     * @note In addition to negating the angle, we negate the sine value
     */
    CachingDms operator-();
 
    /**
     * @short Casting constructor
     */
    CachingDms(const dms &angle);
 
#ifdef COUNT_DMS_SINCOS_CALLS
    /**
     * Copy constructor that sets m_cacheUsed to true
     */
    CachingDms(const CachingDms &o);
    CachingDms &operator=(const CachingDms &o);
#endif
 
  private:
    double m_sin, m_cos; // Cached values
 
    /**
     * @short Private constructor used to create a CachingDms with known sine and cosine
     */
    explicit CachingDms(const double &degrees, const double &sine, const double &cosine)
        : dms(degrees), m_sin(sine), m_cos(cosine)
    {
#ifdef COUNT_DMS_SINCOS_CALLS
        ++cachingdms_constructor_calls;
        m_cacheUsed = false;
#endif
    }
 
    /**
     * @short Addition and subtraction operators
     * @note Uses trigonometric identities to find the new trigonometric values
     * @note Avoid repeated use, as the round-off errors will accumulate!
     */
    friend CachingDms operator+(const CachingDms &, const CachingDms &);
    friend CachingDms operator-(const CachingDms &, const CachingDms &);
    friend CachingDms operator+(const dms &a, const CachingDms &b);
    friend CachingDms operator-(const dms &a, const CachingDms &b);
    friend CachingDms operator+(const CachingDms &a, const dms &b);
    friend CachingDms operator-(const CachingDms &a, const dms &b);
 
#ifdef COUNT_DMS_SINCOS_CALLS
  private:
    mutable bool m_cacheUsed;
 
  public:
    static unsigned long cachingdms_constructor_calls;
    static long cachingdms_delta; // difference of ( trig function calls ) - ( trig computations )
    static unsigned long cachingdms_bad_uses;
#endif
};