Implement Ohm's law

Author: dbrgn

src/lib.rs

@@ -160,6 +160,7 @@ impl_maths!(Power, Force, Speed);
 impl_maths!(Speed, time::Duration, Acceleration);
 impl_maths!(Volume, Length, Area);
 impl_maths!(Power, AngularVelocity, Torque);
+impl_maths!(Voltage, Resistance, Current);
 
 // Force * Distance is ambiguous. Create an ambiguous struct the user can then
 // cast into either Torque or Energy.

src/voltage.rs

@@ -90,6 +90,8 @@ implement_measurement! { Voltage }
 #[cfg(test)]
 mod test {
     use voltage::*;
+    use resistance::*;
+    use current::*;
     use test_utils::assert_almost_eq;
 
     #[test]
@@ -168,4 +170,28 @@ mod test {
         assert_eq!(a >= b, false);
     }
 
+    #[test]
+    fn mul_resistance_current() {
+        let r = Resistance::from_ohms(470.0);
+        let i = Current::from_amperes(2.0);
+        let u = r * i;
+        assert_eq!(u.as_volts(), 940.0);
+    }
+
+    #[test]
+    fn div_resistance() {
+        let r = Resistance::from_ohms(470.0);
+        let u = Voltage::from_kilovolts(4.7);
+        let i = u / r;
+        assert_eq!(i.as_amperes(), 10.0);
+    }
+
+    #[test]
+    fn div_current() {
+        let i = Current::from_amperes(10.0);
+        let u = Voltage::from_kilovolts(4.7);
+        let r = u / i;
+        assert_eq!(r.as_ohms(), 470.0);
+    }
+
 }