Tuples

Before we can start describing the basic hash table functions, we first need to create a way to handle key-value pairs. We generally refer to any piece of data that has two parts as a tuple. In the case of key-value pairs, our tuple would look like (key, value). Some languages, such as Python, provide built-in support for creating tuples, while others such as Java and C# require us to create our own tuple class, which is easy to do. All we really need our tuple class to do is to allow us to:

1. create a tuple consisting of two objects,
2. access either of the two parts of the tuple,
3. check two tuples for equality, and
4. convert the tuple to a string.

The pseudocode for the Tuple class is given below. Each of the operations is simple and thus we do not discuss them individually. However, notice that the class has two attributes, key and value, that are created in the constructor. The getKey and getValue operations are used often in the code below to provide access to the internals of the tuples.

class Tuple	
    object key = null
    object value = null

    function Tuple(object k, object v)
        key = k
        value = v
    end function

    function getKey() returns string
        return key
    end function

    function getValue() returns object
        return value
    end function

    function toString() returns string
        return "(" + key.toString() + "," + value.toString() + ")"
    end function

    function equals(Object o) returns boolean
        if o is not an instance of Tuple:
            return false
        end if
        Tuple t = (Tuple)o
        return (o.key == key) AND (o.value == value)
    end function