\section{Problem 3}
-\emph{The goal of this problem is to exploit the power of the recom mended
+\emph{The goal of this problem is to exploit the power of the recommended
tools rather than elaborating the questions by hand.}
\begin{enumerate}[a.]
\item\emph{In mathematics, a \emph{group} is defined to be a set $G$
\end{lstlisting}
\textsc{prover9} fails to find a proof for $x*y=y*x$.
+ Running the same file with \textsc{mace4} gives the following
+ counterexample.
- \item\emph{A term rewrite sysetm consists of the single rule
+ \item\emph{A term rewrite system consists of the single rule
$$a(x,a(y,a(z,u)))\rightarrow a(y,a(z,a(x,u))),$$
in which $a$ is a binary symbol and $x,y,z,u$ are variables.
Moreover, there are constants $b,c,d,e,f,g$. Determine whether
values of the position variables is
$$p_0=b,p_1=c,p_2=d,p_3=e,p_4=f,p_5=b$$
There are four possible transitions and they are put in a
- disjuction and shown below:
+ disjunction and shown below:
$$\begin{array}{rl}
next(m)=1 \wedge & next(p_0)=p_1 \wedge next(p_1)=p_2
\wedge next(p_2)=p_0 \wedge\\
p_3=e\wedge p_4=f\wedge p_5=b)$$
The solution described below is found by
- \textsc{NuSMV} within $0.01$ seconds. Overline triples are the
+ \textsc{NuSMV} within $0.01$ seconds. Overlined triples are the
ones changed in the next.
$$\begin{array}{rl}
\overline{b,c,d},e,f,b
& \rightarrow b,\overline{d,c,e},f,b\\
& \rightarrow b,c,e,d,f,b\\
\end{array}$$
-
-
-
\end{enumerate}