You can redefine or overload most of the built-in operators available in F#. Thus a programmer can use operators with user-defined types as well.
Operators are functions with special names, enclosed in brackets. They must be defined as static class members. Like any other function, an overloaded operator has a return type and a parameter list.
The following example, shows a + operator on complex numbers −
//overloading + operator static member (+) (a : Complex, b: Complex) = Complex(a.x + b.x, a.y + b.y)
The above function implements the addition operator (+) for a user-defined class Complex. It adds the attributes of two objects and returns the resultant Complex object.
The following program shows the complete implementation −
//implementing a complex class with +, and - operators //overloaded type Complex(x: float, y : float) = member this.x = x member this.y = y //overloading + operator static member (+) (a : Complex, b: Complex) = Complex(a.x + b.x, a.y + b.y) //overloading - operator static member (-) (a : Complex, b: Complex) = Complex(a.x - b.x, a.y - b.y) // overriding the ToString method override this.ToString() = this.x.ToString() + " " + this.y.ToString() //Creating two complex numbers let c1 = Complex(7.0, 5.0) let c2 = Complex(4.2, 3.1) // addition and subtraction using the //overloaded operators let c3 = c1 + c2 let c4 = c1 - c2 //printing the complex numbers printfn "%s" (c1.ToString()) printfn "%s" (c2.ToString()) printfn "%s" (c3.ToString()) printfn "%s" (c4.ToString())
When you compile and execute the program, it yields the following output −
7 5 4.2 3.1 11.2 8.1 2.8 1.9