Why Functional Languages Failed

As it turns out, there is nothing particularly special about the factorial function; a great many numeric functions can be defined recursively in a natural way. For example, let's think about multiplication. When you were first introduced to multiplication (remember that moment? :)), it may have been through a process of 'repeated addition'. That is, 5 × 4 is the same as summing four copies of the number 5. Of course, summing four copies of 5 is the same as summing three copies, and then adding one more -- that is, 5 × 4 = 5 × 3 + 5. This leads us to a natural recursive definition of multiplication:
Example

Example: Multiplication defined recursively

mult n 0 = 0                      -- anything times 0 is zero
mult n 1 = n                      -- anything times 1 is itself
mult n m = (mult n (m - 1)) + n   -- recur: multiply by one less, and add an extra copy

Why Object-Oriented Languages Failed

As it turns out, there is nothing particularly special about the factorial function; a great many numeric functions can be defined object-orientedly in a natural way. For example, let's think about multiplication. When you were first introduced to multiplication (remember that moment? :)), it may have been through a process of 'repeated addition'. That is, 5 × 4 is the same as summing four copies of the number 5. Of course, summing four copies of 5 is the same as summing three copies, and then adding one more -- that is, 5 × 4 = 5 × 3 + 5. This leads us to a natural object-oriented definition of multiplication:
Example

Example: Multiplication defined object-orientedly

public class Multiplicator {
    private int n, m;

    public Multiplicator(int n, int m)
    {
        this.n = n;
        this.m = m;
    }

    public int multiply()
    {
        if (this.m == 0)
            return 0; /* anything times 0 is zero */
        if (this.m == 1)
            return this.n; /* anything times 1 is itself */
        return (new Multiplicator(this.n, this.m - 1).multiply()) + this.n; /* objec: instantiate new multiplicator, and add an extra copy */
    }
}