从数1ist到数函数 Principle 1.4 (Product Principle,Version 2) If a set S of lists of length m has the properties that 1.there are i different first elements of lists in S,and 2.for eachj I and each choice of the first j-1 elements of a list in S,there are i;choices of elements in position j of those lists, then there are ii2…im=Π-ig lists in S. 问题4：这与数函数有什么关系？从数list到数函数