Add operator overloads for MassFlow, VolumeFlow and Density (#430)

Author: patchandthat

UnitsNet.Tests/CustomCode/MassFlowTests.cs

@@ -118,5 +118,19 @@ public void MassFlowDividedByMassFluxEqualsArea()
             Area area = MassFlow.FromKilogramsPerSecond(20) / MassFlux.FromKilogramsPerSecondPerSquareMeter(2);
             Assert.Equal(10, area.SquareMeters);
         }
+
+        [Fact]
+        public void MassFlowDividedByVolumeFlowEqualsDensity()
+        {
+            Density density = MassFlow.FromKilogramsPerSecond(12) / VolumeFlow.FromCubicMetersPerSecond(3);
+            Assert.Equal(4, density.KilogramsPerCubicMeter);
+        }
+
+        [Fact]
+        public void MassFlowDividedByDensityEqualsVolumeFlow()
+        {
+            VolumeFlow volumeFlow = MassFlow.FromKilogramsPerSecond(20) / Density.FromKilogramsPerCubicMeter(4);
+            Assert.Equal(5, volumeFlow.CubicMetersPerSecond);
+        }
     }
 }

UnitsNet.Tests/CustomCode/VolumeFlowTests.cs

@@ -121,5 +121,19 @@ public void VolumeFlowDividedBySpeedEqualsArea()
             Area area = VolumeFlow.FromCubicMetersPerSecond(40) / Speed.FromMetersPerSecond(20);
             Assert.Equal(Area.FromSquareMeters(2), area);
         }
+
+        [Fact]
+        public void VolumeFlowTimesDensityEqualsMassFlow()
+        {
+            MassFlow massFlow = VolumeFlow.FromCubicMetersPerSecond(2) * Density.FromKilogramsPerCubicMeter(3);
+            Assert.Equal(MassFlow.FromKilogramsPerSecond(6), massFlow);
+        }
+
+        [Fact]
+        public void DensityTimesVolumeFlowEqualsMassFlow()
+        {
+            MassFlow massFlow = Density.FromKilogramsPerCubicMeter(3) * VolumeFlow.FromCubicMetersPerSecond(7);
+            Assert.Equal(MassFlow.FromKilogramsPerSecond(21), massFlow);
+        }
     }
 }

UnitsNet/CustomCode/Quantities/MassFlow.extra.cs

@@ -80,6 +80,16 @@ public partial struct MassFlow
         {
             return Area.FromSquareMeters(massFlow.KilogramsPerSecond / massFlux.KilogramsPerSecondPerSquareMeter);
         }
+
+        public static Density operator /(MassFlow massFlow, VolumeFlow volumeFlow)
+        {
+            return Density.FromKilogramsPerCubicMeter(massFlow.KilogramsPerSecond / volumeFlow.CubicMetersPerSecond);
+        }
+
+        public static VolumeFlow operator /(MassFlow massFlow, Density density)
+        {
+            return VolumeFlow.FromCubicMetersPerSecond(massFlow.KilogramsPerSecond / density.KilogramsPerCubicMeter);
+        }
 #endif
     }
-}
+}

UnitsNet/CustomCode/Quantities/VolumeFlow.extra.cs

@@ -53,6 +53,16 @@ public partial struct VolumeFlow
         {
             return Area.FromSquareMeters(volumeFlow.CubicMetersPerSecond / speed.MetersPerSecond);
         }
+
+        public static MassFlow operator *(VolumeFlow volumeFlow, Density density)
+        {
+            return MassFlow.FromKilogramsPerSecond(volumeFlow.CubicMetersPerSecond * density.KilogramsPerCubicMeter);
+        }
+
+        public static MassFlow operator *(Density density, VolumeFlow volumeFlow)
+        {
+            return MassFlow.FromKilogramsPerSecond(volumeFlow.CubicMetersPerSecond * density.KilogramsPerCubicMeter);
+        }
 #endif
     }
 }