Implement function overloading in Haskell

Question

I am working on the problem for writing Haskell code similar to a C++ program.

The C++ code is:

class Rectangle
{
    private:
        int length;
        int width;
    public:
        Rectangle()
        {
            length = 0;
            width = 0;
        }
        Rectangle(int x)
        {
            length = x;
            width =0;
        }
        Rectangle ( int x , int y)
        {
            length = x;
            width = y;
        }
};

To write similar Haskell code i made a data type Rectangle

data Rectangle = Rectangle Length Width deriving (Eq, Show , Read)
type Length = Int
type Width = Int

Then i thought of making a load function which can act as constructor. But i don't understand how to implement function overloading with different number of arguments. Please help. Thanks.

Answer 1

You can use record syntax to reach that behavior.

data Rectangle = Rectangle {len :: Length, width :: Width} deriving (Eq, Show , Read)
type Length = Int
type Width = Int

rectangle = Rectangle { len = 0, width = 0 }

rectangle :: Rectangle will be your constructor here.

Now you can define some Rectangle values:

λ> let a = rectangle {len = 1}

λ> a
Rectangle {len = 1, width = 0}