Define a pure function delta that takes a function f as an argument and computes the forward difference of f. The mathematical definition of the forward difference operator, written A, is Af(x) = f(x + 1) - f(x) Note that the argument f is a function, as is the value returned by delta. That is, delta is a higher-order function. You will want to use a lambda expression in your solution. The following fact may help you test your implementation: For all numbers n, ((delta (lambda (x) x)) n) should be equal to 1 (why?).