问题
I have been trying to learn Prolog, and am totally stumped on what the predicate s() does. I see it used often and there is so little resources on the internet about Prolog that I cannot find an answer.
Ex.
/* sum(Is,S) is true if S is the sum of the list of integers Is. */
sum([],0).
sum([0|Is],S):-sum(Is,S).
sum([s(I)|Is], s(Z) ):-sum([I|Is],Z).
回答1:
s/1
does not do anything in itself, and it's not really a predicate. They are just terms, a representation of the successor of their argument. So, s(0)
is used to represent the successor of 0
(i.e. 1
), s(s(0))
is used to represent the successor of s(0)
(i.e. 2
), and so on and so forth. They are so widespread in Prolog because Prolog is quite fine a language to perform symbolic computation, whereas even simple arithmetic operations feel clunky, meaning that they are not seamlessly integrated with the programming paradigm.
回答2:
s/1 stands for successor. It's used to represent numbers in a logically accessible ways.
回答3:
It is Prolog-implementation specific. It refers to a successor-predicate, see this for some more info
来源:https://stackoverflow.com/questions/8197088/what-does-the-s-predicate-do-in-prolog