The example above did not return any value. But functions are to return values. To return a value from a function the code should perform an assignment that looks very similar to a normal assignment statement. The difference is that the "variable" that stands on the left side of the = should be the name of the function. Let's see the previous example a bit extended:
x = a * b * c
MyFunction = a + b + c
a = MyFunction(1,2,MyFunction(1,1,1))
print a,b,c,x printnl x = a * b * c MyFunction = a + b + c
The output is
The value of the function call is 3 when the function is first executed. This value is passed to the function call itself as third argument; and is used to calculate the final values for the variable a.