unit: add more complex example

unit/unitexample_test.go

@@ -27,3 +27,23 @@ func ExampleNewDimension() {
 
 	// Output: 0.1 tree m^-2
 }
+
+func Example_horsepower() {
+	// One mechanical horsepower ≡ 33,000 ft-lbf/min.
+	foot := unit.Length(0.3048)
+	pound := unit.Mass(0.45359237)
+
+	gravity := unit.New(9.80665, unit.Dimensions{unit.LengthDim: 1, unit.TimeDim: -2})
+	poundforce := pound.Unit().Mul(gravity)
+
+	hp := ((33000 * foot).Unit().Mul(poundforce)).Div(unit.Minute)
+	fmt.Println("1 hp =", hp)
+
+	watt := unit.New(1, unit.Dimensions{unit.MassDim: 1, unit.LengthDim: 2, unit.TimeDim: -3})
+	fmt.Println("W is equivalent to hp?", unit.DimensionsMatch(hp, watt))
+
+	// Output:
+	//
+	// 1 hp = 745.6998715822701 kg m^2 s^-3
+	// W is equivalent to hp? true
+}