f(x) def = x + 1 for any integer x. Given a program Π and a value x, it is possible to compute f(x), where f(·) is the function associated with the program Π, by executing the program Π on a computer. We sometimes call the string Π the representation or code of the function f(·). Since a program is a string, it sometimes makes sense to use it as input to a different program. Indeed, algorithms ...