[PQ] Add unary minus operator

src/blackmisc/pq/physicalquantity.cpp

@@ -237,6 +237,14 @@ namespace BlackMisc
             return copy;
         }
 
+        template <class MU, class PQ>
+        PQ CPhysicalQuantity<MU, PQ>::operator -() const
+        {
+            PQ copy = *derived();
+            copy *= -1;
+            return copy;
+        }
+
         template <class MU, class PQ>
         bool CPhysicalQuantity<MU, PQ>::lessThan(const CPhysicalQuantity<MU, PQ> &other) const
         {

src/blackmisc/pq/physicalquantity.h

@@ -165,6 +165,9 @@ namespace BlackMisc
             //! Operator /
             PQ operator /(double divide) const;
 
+            //! Unary operator -
+            PQ operator -() const;
+
             //! Equal operator ==
             friend bool operator==(const CPhysicalQuantity &a, const CPhysicalQuantity &b) { return a.equals(b); }
 

tests/blackmisc/pq/testphysicalquantities/testphysicalquantities.cpp

@@ -97,6 +97,12 @@ namespace BlackMiscTest
         CFrequencyUnit fu1 = CFrequencyUnit::Hz();
         QVERIFY2(fu1 != du1, "Hz must not be meter");
 
+        // Unary expressions
+        CTemperature temp1(5, CTemperatureUnit::C());
+        QVERIFY2(-temp1 == CTemperature(-5, CTemperatureUnit::C()), "Temperatures must be the same");
+        CTemperature temp2(-8.7, CTemperatureUnit::K());
+        QVERIFY2(-temp2 == CTemperature(8.7, CTemperatureUnit::K()), "Temperatures must be the same");
+
         // null comparisons
         const CLength null(CLength::null());
         const CLength nonNull(1, CLengthUnit::m());