The program shows a numeric entry field at the bottom and a number display at the top. Whenever the user enters a number in the entry field and presses Return the factorial of that number is computed and displayed in the number display.
Here is the source code:
import Fudgets main = fudlogue (shellF "Fac" facF) facF = intDispF >==< mapF fac >==< intInputF fac 0 = 1 fac n = n * fac (n-1)
facF) is structured as a serial composition of three parts, using the operator
>==<, Notice that data flow from right to left. The parts are:
mapF fac, an abstract fudget that applies
fac, the factorial function, to integers received from the entry field, and
intDispFwhich displays the factorials.
shellFon the top level as in the previous examples.