refs #126 null unit infrastructure, a sentinel to mark an uninitialized or unused physical quantity

src/blackmisc/pqbase.cpp

@@ -39,8 +39,7 @@ namespace BlackMisc
          */
         double CMeasurementUnit::convertFrom(double value, const CMeasurementUnit &unit) const
         {
-            Q_ASSERT(this->m_converter);
+            if (this->isNull() || unit.isNull()) return -1; // models the previous behaviour of using -1 as a sentinel value
-            Q_ASSERT(unit.m_converter);
             if (this->m_converter == unit.m_converter) return value;
             return this->m_converter->fromDefault(unit.m_converter->toDefault(value));
         }

src/blackmisc/pqbase.h

@@ -16,6 +16,7 @@
 #include <QSharedData>
 #include <QSharedDataPointer>
 #include <QHash>
+#include <cstddef>
 
 namespace BlackMisc
 {
@@ -214,6 +215,13 @@ namespace BlackMisc
                 : m_name(name), m_symbol(symbol), m_epsilon(epsilon), m_displayDigits(displayDigits), m_converter(new Converter)
             {}
 
+            /*!
+             * Construct a null unit
+             */
+            CMeasurementUnit(const QString &name, const QString &symbol, std::nullptr_t)
+                : m_name(name), m_symbol(symbol), m_epsilon(0.0), m_displayDigits(0)
+            {}
+
             //! \copydoc CValueObject::stringForStreaming
             virtual QString stringForStreaming() const override
             {
@@ -348,6 +356,14 @@ namespace BlackMisc
                 return abs(value) <= this->m_epsilon;
             }
 
+            /*!
+             * \brief Is unit null?
+             */
+            bool isNull() const
+            {
+                return this->m_converter.data() == nullptr;
+            }
+
             // --------------------------------------------------------------------
             // -- static
             // --------------------------------------------------------------------

src/blackmisc/pqphysicalquantity.h

@@ -125,6 +125,14 @@ namespace BlackMisc
              */
             PQ &switchUnit(const MU &newUnit);
 
+            /*!
+             * Is quantity null?
+             */
+            bool isNull() const
+            {
+                return this->m_unit.isNull();
+            }
+
             /*!
              * \brief Value in given unit
              */

src/blackmisc/pqunits.h

@@ -37,6 +37,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CLengthUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             struct NauticalMilesToMeters    { static double factor() { return 1852.0;    } };
             struct FeetToMeters             { static double factor() { return    0.3048; } };
             struct MilesToMeters            { static double factor() { return 1609.344;  } };
@@ -62,6 +66,15 @@ namespace BlackMisc
              */
             static const CLengthUnit &defaultUnit() { return m(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CLengthUnit &nullUnit()
+            {
+                static CLengthUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Meter m
              */
@@ -133,6 +146,7 @@ namespace BlackMisc
                 static QList<CLengthUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CLengthUnit::nullUnit());
                     u.append(CLengthUnit::cm());
                     u.append(CLengthUnit::ft());
                     u.append(CLengthUnit::km());
@@ -167,6 +181,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CAngleUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             struct RadiansToDegrees { static double factor() { return 180.0 / M_PI; } };
             typedef One DegreesToDegrees;
 
@@ -189,6 +207,15 @@ namespace BlackMisc
              */
             static const CAngleUnit &defaultUnit() { return deg(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CAngleUnit &nullUnit()
+            {
+                static CAngleUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \copydoc CMeasurementUnit::makeRoundedQStringWithUnit
              */
@@ -242,6 +269,7 @@ namespace BlackMisc
                 static QList<CAngleUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CAngleUnit::nullUnit());
                     u.append(CAngleUnit::deg());
                     u.append(CAngleUnit::rad());
                     u.append(CAngleUnit::sexagesimalDeg());
@@ -273,6 +301,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CFrequencyUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             typedef One HertzToHertz;
 
         public:
@@ -294,6 +326,15 @@ namespace BlackMisc
              */
             static const CFrequencyUnit &defaultUnit() { return Hz(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CFrequencyUnit &nullUnit()
+            {
+                static CFrequencyUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Hertz
              */
@@ -338,6 +379,7 @@ namespace BlackMisc
                 static QList<CFrequencyUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CFrequencyUnit::nullUnit());
                     u.append(CFrequencyUnit::GHz());
                     u.append(CFrequencyUnit::Hz());
                     u.append(CFrequencyUnit::kHz());
@@ -369,6 +411,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CMassUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             typedef Milli<One> GramsToKilograms;
             struct PoundsToKilograms { static double factor() { return 0.45359237; } };
 
@@ -391,6 +437,15 @@ namespace BlackMisc
              */
             static const CMassUnit &defaultUnit() { return kg(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CMassUnit &nullUnit()
+            {
+                static CMassUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Kilogram, SI base unit
              */
@@ -444,6 +499,7 @@ namespace BlackMisc
                 static QList<CMassUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CMassUnit::nullUnit());
                     u.append(CMassUnit::g());
                     u.append(CMassUnit::kg());
                     u.append(CMassUnit::lb());
@@ -476,6 +532,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CPressureUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             typedef Centi<One> PascalsToHectopascals;
             struct PsiToHectopascals            { static double factor() { return  68.948;      } };
             struct InchesToHectopascals         { static double factor() { return  33.86389;    } };
@@ -500,6 +560,15 @@ namespace BlackMisc
              */
             static const CPressureUnit &defaultUnit() { return hPa(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CPressureUnit &nullUnit()
+            {
+                static CPressureUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Pascal
              */
@@ -571,6 +640,7 @@ namespace BlackMisc
                 static QList<CPressureUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CPressureUnit::nullUnit());
                     u.append(CPressureUnit::bar());
                     u.append(CPressureUnit::hPa());
                     u.append(CPressureUnit::inHg());
@@ -604,6 +674,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CTemperatureUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             struct KelvinToCentigrade
             {
                 static double factor() { return 1.0; }
@@ -634,6 +708,15 @@ namespace BlackMisc
              */
             static const CTemperatureUnit &defaultUnit() { return C(); }
 
+            /*!
+             * \brief Null unit
+             */
+            static const CTemperatureUnit &nullUnit()
+            {
+                static CTemperatureUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Kelvin
              */
@@ -669,6 +752,7 @@ namespace BlackMisc
                 static QList<CTemperatureUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CTemperatureUnit::nullUnit());
                     u.append(CTemperatureUnit::C());
                     u.append(CTemperatureUnit::F());
                     u.append(CTemperatureUnit::K());
@@ -699,6 +783,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CSpeedUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             struct KnotsToMps       { static double factor() { return 1852.0    / 3600.0; } };
             struct KphToMps         { static double factor() { return    1.0    /    3.6; } };
             struct FtPerSecToMps    { static double factor() { return    0.3048         ; } };
@@ -723,6 +811,15 @@ namespace BlackMisc
              */
             static const CSpeedUnit &defaultUnit() { return m_s(); }
 
+            /*!
+             * Null unit
+             */
+            static const CSpeedUnit &nullUnit()
+            {
+                static CSpeedUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Meter/second m/s
              */
@@ -785,6 +882,7 @@ namespace BlackMisc
                 static QList<CSpeedUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CSpeedUnit::nullUnit());
                     u.append(CSpeedUnit::ft_min());
                     u.append(CSpeedUnit::ft_s());
                     u.append(CSpeedUnit::km_h());
@@ -818,6 +916,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CTimeUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             typedef One SecondsToSeconds;
             struct DaysToSeconds    { static double factor() { return 60.0 * 60.0 * 24.0;   } };
             struct HoursToSeconds   { static double factor() { return 60.0 * 60.0;          } };
@@ -842,6 +944,15 @@ namespace BlackMisc
              */
             static const CTimeUnit &defaultUnit() { return s(); }
 
+            /*!
+             * Null unit
+             */
+            static const CTimeUnit &nullUnit()
+            {
+                static CTimeUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \copydoc CMeasurementUnit::makeRoundedQStringWithUnit
              */
@@ -933,6 +1044,7 @@ namespace BlackMisc
                 static QList<CTimeUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CTimeUnit::nullUnit());
                     u.append(CTimeUnit::d());
                     u.append(CTimeUnit::h());
                     u.append(CTimeUnit::min());
@@ -965,6 +1077,10 @@ namespace BlackMisc
                 CMeasurementUnit(name, symbol, converter, displayDigits, epsilon)
             {}
 
+            CAccelerationUnit(const QString &name, const QString &symbol, std::nullptr_t) :
+                CMeasurementUnit(name, symbol, nullptr)
+            {}
+
             struct FeetToMeters { static double factor() { return 0.3048; } };
 
         public:
@@ -986,6 +1102,15 @@ namespace BlackMisc
              */
             static const CAccelerationUnit &defaultUnit() { return m_s2(); }
 
+            /*!
+             * Null unit
+             */
+            static const CAccelerationUnit &nullUnit()
+            {
+                static CAccelerationUnit nu("null", "null", nullptr);
+                return nu;
+            }
+
             /*!
              * \brief Meter/second^2 (m/s^2)
              */
@@ -1012,6 +1137,7 @@ namespace BlackMisc
                 static QList<CAccelerationUnit> u;
                 if (u.isEmpty())
                 {
+                    u.append(CAccelerationUnit::nullUnit());
                     u.append(CAccelerationUnit::ft_s2());
                     u.append(CAccelerationUnit::m_s2());
                 }