Tla+ 如何将公式转换为TLA+；代码

我已经写了一份关于河内塔问题的TLA+规范：

TEX

ASCII

------------------------------- MODULE Hanoi -------------------------------

EXTENDS Sequences, Integers
VARIABLE A, B, C


CanMove(x,y) == /\ Len(x) > 0 
                /\ IF Len(y) > 0 THEN Head(y) > Head(x) ELSE TRUE

Move(x,y,z) == /\ CanMove(x,y)
               /\ x' = Tail(x)
               /\ y' = <<Head(x)>> \o y
               /\ z' = z

Invariant == C /= <<1,2,3>>   \* When we win!                           

Init == /\ A = <<1,2,3>>
        /\ B = <<>>
        /\ C = <<>>

Next == \/ Move(A,B,C) \* Move A to B
        \/ Move(A,C,B) \* Move A to C
        \/ Move(B,A,C) \* Move B to A
        \/ Move(B,C,A) \* Move B to C
        \/ Move(C,A,B) \* Move C to A
        \/ Move(C,B,A) \* Move C to B
=============================================================================

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我如何用TLA语言表达它呢？

不应该使用变量A、B、C，而应该使用一个序列，

塔

，其中塔是索引。这还有一个优点，即塔的数量是通用的。您的

Next

公式也将更短：

CanMove(i,j) == /\ Len(towers[i]) > 0 
                /\ Len(towers[j]) = 0 \/ Head(towers[j]) > Head(towers[i])

Move(i, j) == /\ CanMove(i, j)
              /\ towers' = [towers EXCEPT ![i] = Tail(@),
                                          ![j] = <<Head(towers[i])>> \o @]

Init == towers = << <<1,2,3>>, <<>>, <<>> >> \* Or something more generic

Next == \E i, j \in DOMAIN towers: i /= j /\ Move(i, j)

CanMove(i,j) == /\ Len(towers[i]) > 0 
                /\ Len(towers[j]) = 0 \/ Head(towers[j]) > Head(towers[i])

Move(i, j) == /\ CanMove(i, j)
              /\ towers' = [towers EXCEPT ![i] = Tail(@),
                                          ![j] = <<Head(towers[i])>> \o @]

Init == towers = << <<1,2,3>>, <<>>, <<>> >> \* Or something more generic

Next == \E i, j \in DOMAIN towers: i /= j /\ Move(i, j)

Init == towers = [a |-> <<1, 2, 3>>, b |-> <<>>, c |-> <<>>]