【发布时间】:2015-04-19 17:04:40
【问题描述】:
我需要将以下 FOL 句子表述为 Prolog 规则,并且完全不知道如何做到这一点。 (我是 Prolog 的新手):
“如果两个终端相连,则它们具有相同的信号。” 在一阶逻辑中,这将是:
FORALL(T1, T2) : Terminal(T1) AND Terminal(T2) AND Connected(T1, T2) => Signal(T1) = Signal(T2)
我知道,“and”是如何用 Prolog 编写的,而且你不需要 FORALL。我的问题是,左侧只能是一个谓词。 这是一个更大问题的一部分,完整的规则集是:
- 如果两个端子相连,则它们具有相同的信号
- 连通是可交换的
- 每个终端的信号不是1就是0
- 有四种类型的门(and、or、xor、neg)
- 与门的输出为 0 当且仅当其任何输入为 0 时
- 当且仅当其任何输入为 1 时,或门的输出为 1
- 当且仅当输入不同时,异或门的输出为 1
- 否定门的输出与输入不同
- 门(除了 neg)有两个输入和一个输出
- 电路的输入和输出数量达到其极限,并且没有超出其数量的端子
- 门、终端、信号、门类型和任何东西都是不同的
- 门是电路
我目前正在制定规则,我会在完成后立即发布。这是我到目前为止所拥有的(第一行 % 是自然语言,第二行 % 是直观的 FOL 表示,之后的行是我对 Prolog 规则的尝试):
%If two terminals are connected, then they have the same signal:
%all(T1, T2) : terminal(T1), terminal(T2), connected(T1, T2) => signal(T1) = signal(T2).
same_value(T1, T2) :- terminal(T1), terminal(T2), connected(T1, T2).
%Connected is commutative:
%all(T1, T2) :- connected(T1, T2) <=> connected(T2, T1).
connected(T1, T2) :- connected(T2, T1).
%The signal at every terminal is either 1 or 0:
%all(T) :- terminal(T) => signal(T) == 1; signal(T) == 0.
terminal(T) :- signal(T) = 1; signal(T) = 0.
%There are four types of gates:
%all(G) :- (gate(G), K = type(G)) => (K == and; K == or; K == xor; K == neg).
%An and gate's output is 0 if and only if any of its inputs is 0:
%all(G) :- gate(G), type(G) == and => signal(out(1, G)) = 0 <=> some(N), signal(in(N, G)) == 0.
signal(out(1, G)) :- (gate(G), type(G) == or, signal(in(1, G)) == 0; signal(in(2, G)) == 0) => 0.
signal(out(1, G)) :- (gate(G), type(G) == or, signal(in(1, G)) == 1, signal(in(2, G)) == 1) => 1.
%this produces an error: Operator expected
%An or gate's output is 1 if and only if any of its inputs is 1:
%all(G) :- gate(G), type(G) == or => signal(out(1, G)) = 1 <=> some(N), signal(in(N, G)) == 1.
signal(out(1, G)) :- (gate(G), type(G) == or, signal(in(1, G)) == 0, signal(in(2, G)) == 0) => 0.
signal(out(1, G)) :- (gate(G), type(G) == or, signal(in(1, G)) == 1; signal(in(2, G)) == 1) => 1.
%this produces an error: Operator expected
%An xor gate's output is 1 if and only if its inputs are different:
%all(G) :- gate(G), type(G) == xor => signal(out(1, G)) = 1 <=> signal(in(1, G)) \= signal(in(2, G)).
signal(out(1, G)) :- (gate(G), type(G) == xor, signal(in(1, G)) == signal(in(2, G))) => 0.
signal(out(1, G)) :- (gate(G), type(G) == xor, signal(in(1, G)) \= signal(in(2, G))) => 1.
%this produces an error: Operator expected
%A neg gate's output is different from its input:
%all(G) :- gate(G), type(G) == neg => signal(out(1, G)) = not(signal(in(1, G))).
signal(out(1, G)) :- (gate(G), type(G) == neg, signal(in(1, G)) == 1) => 0.
signal(out(1, G)) :- (gate(G), type(G) == neg, signal(in(1, G)) == 0) => 1.
%this produces an error: Operator expected
%The gates (except for neg) have two inputs and one output:
%all(G) :- gate(G), type(G) == neg => arity(G, 1, 1).
%all(G) :- gate(G), K = type(G), (K == and; K == or; K == xor) => arity(G, 2, 1).
arity(G, 1, 1) :- gate(G), type(G) == neg.
arity(G, 2, 1) :- gate(G), (type(G) == and; type(G) == or; type(G) == xor).
%A circuit has terminals up to its input and output arity, and nothing beyond its arity:
%all(C, I, J) :- circuit(C), arity(C, I, J) =>
% all(N), (N =< I => terminal(in(C, N))), (N > I => in(C, N) = nothing),
% all(N), (N =< J => terminal(out(C, N))), (N > J => out(C, N) = nothing).
%Gates, terminals, signals, gate types, and Nothing are all distinct:
%all(G, T) :- gate(G), terminal(T) => G \= T \= 1 \= 0 \= or \= and \= xor \= neg \= nothing.
%Gates are circuits:
%all(G) :- gate(G) => circuit(G).
circuit(G) :- gate(G).
【问题讨论】:
-
您是否通过教程或书籍熟悉了 Prolog?仅供参考,第一个表达式,如果两个终端连接,那么它们具有相同的信号,可以非常直接且简单地翻译成 Prolog 谓词。你不需要 FORALL。
AND非常基本:它是一个逗号。 -
@lurker:这并不完全正确,在 Prolog 中,定义了一个顺序。 答案集编程在许多情况下更好地指定(实际)逻辑。
-
@CommuSoft,我同意,但并非总是如此。我说的是 OP 的表达案例,没有任何额外的信息,这是一个简单的谓词。
标签: prolog