Directions: Use your own paper for answers. When you are done you may keep this exam sheet and should pick up an answer sheet.

1. Consider a shift-reduce parser as we had in a recitation.
   1. In such a parser, say what is being shifted and where it is being shifted to.

   2. Suppose the grammar rule

      
         E ---> E '+' T 
      

      is being used for a reduction. Describe briefly what happens during this reduction.

   3. How does the parser know whether to shift or to reduce?

    

    

    

2. Consider the following slightly modified grammar rule from the course parser assignment:

   
      W  --->  '{' E '?' { S } '}' 
   

   1. What does the portion { S } mean on the right side?

   2. What construct is this rule describing?

   3. Write code or pseudo-code for a function W that could work as part of a recursive descent parser for a grammar including this grammar rule. You should assume that a scanner is given to return tokens, and that separate functions E() and S() are available. Use any convenient notation or language. Do not try to supply I/O statements, header files or other details. Just give the bare code for the parser function W.

    

    

    

    

3. Suppose you are generating MIPS code for an if-then-else construct, using the grammar rule

   
      I  --->  '['  E  '?'  { S }  ':'  { S }  ']' 
   

   1. Show what additional MIPS instructions must be generated inside the function I in order to implement the if-then-else. More specifically, show exactly what MIPS instruction(s) and/or label(s) (if any) would need to be inserted by the I function at the four places below labeled
      # INSERT ...

      
      # Start of code for an if-then-else
      # INSERT EXTRA LABEL(S) AND/OR INSTRUCTION(S) HERE
      # Start of code to evaluate an expression E
         ...
      # Result left in a temporary memory location 144 bytes past
      #   the start of the memory array M.
      # INSERT EXTRA LABEL(S) AND/OR INSTRUCTION(S) HERE
      # Start of code to evaluate the first portion { S }
         ...
      # INSERT EXTRA LABEL(S) AND/OR INSTRUCTION(S) HERE
      # Start of code to evaluate the second portion {S}
         ...
      # INSERT EXTRA LABEL(S) AND/OR INSTRUCTION(S) HERE
      
      
      

      (If you don't remember the exact form of the MIPS instructions, just fake it as well as you can.)

   2. How does the function I find out that the result of evaluating E is going to be in a memory location 144 bytes past the start of M?

    

4. Very briefly say how one can manage to pass a function in Java as a parameter, even though Java does not directly support functions as objects that can be passed.

    

5. This is a question about 2-dimensional arrays in C/C++/Java:
   1. Suppose you declare a variable s in C or C++ using int s[5][4];. Is this stored as an array of 1-dimensional arrays (along with the 1-dimensional arrays), or is it stored just as a single 1-dimensional array? In C/C++ is it possible to create an array stored the other way?

   2. Suppose you declare a variable s in Java using int[][] s = new int[5][4]; Same two questions as in part a.

Points for each problem: 1-25, 2-25, 3-25, 4-10, 5-15.