function derivative
In more explicit terms the "doubling function" may be denoted by g(x) = 2x and the "squaring function" by f(x) = x. The "derivative" now takes the function f(x), defined by the expression "x", as an input, that is all the information—such as that two is sent to four, three is sent to nine, four is sent to sixteen, and so on—and uses this information to output another function, the function g(x) = 2x, as will turn out.
