78 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    79 \begin{frame}[c,fragile]

    80 \frametitle{\mbox{}\hspace{5cm}Factorial}

    81 

    82 \begin{textblock}{7}(0,1.0)\footnotesize

    83 \begin{minipage}{6cm}

    84 \begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none]

    85 .method public static facT(II)I 

    86 .limit locals 2

    87 .limit stack 6

    88   iload 0

    89   ldc 0

    90   if_icmpne If_else_2

    91   iload 1

    92   goto If_end_3

    93 If_else_2:

    94   iload 0

    95   ldc 1

    96   isub

    97   iload 0

    98   iload 1

    99   imul

   100   invokestatic fact/fact/facT(II)I

   101 If_end_3:

   102   ireturn

   103 .end method 

   104 \end{lstlisting}

   105 \end{minipage}

   106 \end{textblock}

   107 

   108 \begin{textblock}{7}(6,7)

   109 \begin{bubble}[7cm]\small

   110 \begin{lstlisting}[language=Lisp,

   111                    basicstyle=\ttfamily, 

   112                    numbers=none,

   113                    xleftmargin=1mm,linebackgroundcolor=\color{cream}]

   114 def facT(n, acc) = 

   115   if n == 0 then acc 

   116   else facT(n - 1, n * acc);

   117 \end{lstlisting}

   118 \end{bubble}

   119 \end{textblock}

   120 

   121 \end{frame}

   122 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   123 

   124 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   125 \begin{frame}[fragile]

   126 

   127 \begin{textblock}{7}(1,-0.2)\footnotesize

   128 \begin{minipage}{6cm}

   129 \begin{lstlisting}[language=JVMIS,basicstyle=\ttfamily, numbers=none, escapeinside={(*@}{@*)}]

   130 .method public static facT(II)I 

   131 .limit locals 2

   132 .limit stack 6

   133 (*@\hl{facT\_Start:} @*)

   134   iload 0

   135   ldc 0

   136   if_icmpne If_else_2

   137   iload 1

   138   goto If_end_3

   139 If_else_2:

   140   iload 0

   141   ldc 1

   142   isub

   143   iload 0

   144   iload 1

   145   imul

   146   (*@\hl{istore 1} @*)

   147   (*@\hl{istore 0} @*)

   148   (*@\hl{goto facT\_Start} @*)

   149 If_end_3:

   150   ireturn

   151 .end method 

   152 \end{lstlisting}

   153 \end{minipage}

   154 \end{textblock}

   155 

   156 \begin{textblock}{7}(6,7)

   157 \begin{bubble}[7cm]\small

   158 \begin{lstlisting}[language=Lisp,

   159                    basicstyle=\ttfamily, 

   160                    numbers=none,

   161                    xleftmargin=1mm,linebackgroundcolor=\color{cream}]

   162 def facT(n, acc) = 

   163   if n == 0 then acc 

   164   else facT(n - 1, n * acc);

   165 \end{lstlisting}

   166 \end{bubble}

   167 \end{textblock}

   168 

   169 \end{frame}

   170 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   

   171 

   172 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   173 \begin{frame}[t, fragile]

   174 \frametitle{Tail Recursion}

   175 

   176 A call to \texttt{f(args)} is usually compiled as\medskip

   177 

   178 {\small\begin{lstlisting}[basicstyle=\ttfamily, numbers=none]

   179   args onto stack

   180   invokestatic  .../f 

   181 \end{lstlisting}}\pause

   182 

   183 

   184 A call is in tail position provided:\medskip

   185 

   186 {\small\begin{itemize}

   187 \item \texttt{if Bexp then \hl{Exp} else \hl{Exp}}

   188 \item \texttt{Exp ; \hl{Exp}}

   189 \item \texttt{Exp  op Exp}

   190 \end{itemize}}\medskip

   191 

   192 then a call \texttt{f(args)} can be compiled as\medskip\small

   193 

   194 \begin{lstlisting}[numbers=none]

   195   prepare environment

   196   jump to start of function

   197 \end{lstlisting}

   198 

   199 \end{frame}

   200 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

   201 

   202 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

   203 \begin{frame}[c, fragile]

   204 \frametitle{Tail Recursive Call}

   205 \footnotesize

   206 

   207 \begin{textblock}{13}(-0.3,3)

   208 \begin{lstlisting}[language=Scala, numbers=none]

   209 def compile_expT(a: Exp, env: Mem, name: String): Instrs = 

   210   ...

   211   case Call(n, args) => if (name == n)

   212   {

   213     val stores =

   214       args.zipWithIndex.map { case (x, y) => i"istore $y" } 

   215 

   216     args.map(a => compile_expT(a, env, "")).mkString ++

   217     stores.reverse.mkString ++ 

   218     i"goto ${n}_Start" 

   219   } else {

   220     val is = "I" * args.length

   221     args.map(a => compile_expT(a, env, "")).mkString ++

   222     i"invokestatic XXX/XXX/${n}(${is})I"

   223   }

   224 \end{lstlisting}

   225 \end{textblock}

   226 

   227 \end{frame}

   228 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%