% vim: set spelllang=nl:
\subsection{\texttt{Cat}}
\label{sec:rules:cat}

\begin{quote}
    + - concatenates the top two strings on the stack. The string pushed earlier
		appears earlier in the resulting string, eg \smurfinline{"Zork" "mid" +}
		would result in the string \texttt{Zorkmid} being placed on the stack.
\end{quote}

De string bovenop de stack wordt toegevoegd aan de string hieronder. Het
resultaat wordt op de stack gezet.

Dit geeft de volgende regel:

$$
\begin{prooftree}
	\trans
		{\pgm}{\ip}{(\push{s1~s2}{\stk''}, \str)}
		{\ip'}{\op}{\st}
	\justifies
	\trans
		{\StmCat:\pgm}{\ip}{(\stk,\str)}
		{\ip'}{\op}{\st}
	\using{\rcatns}
	\qquad
	\text{met\enspace
		\parbox{36mm}{$(s_2,\stk') = \pop{\stk}$,\\$(s_1,\stk'') = \pop{\stk'}$.}
	}
\end{prooftree}
$$