CS314 Fall 2007
Assignment 7


#1.  The following expressions in a C-like PL describe constructed
types.  Write out the types of each variable using type
constructors. For example, int *p would be written as Pointer(int)
where int is the base type, and Pointer() is a type constructor that
creates pointers to objects of its parameter type. Write out the types
of each variable in the program given below: Explicitly state any
assumptions you have to use.

 type ss 1..10
 type tt 5..15
 type s struct {int a1, ss a2}
 type t struct {int b1, tt b2}
 type w t[1..10]

 ss s1;
 tt s2;
 s y1;
 t y2;
 w h1;
 s *l1;

#2. Assume your PL allows arrays of the form: a [1..10] [1..5,1..5],
where arrays are stored in column major order.  Show the array element
address formula for a[j][k,l]. State any additional assumptions you
have to make to obtain this formula.

#3. Look at following pseudocode for procedure compute().  You can
assume that this PL allows mixtures of parameter passing methods, as
shown in the procedure definition.


procedure compute(first:integer(by value), last:integer(by value),
     incr:integer(by value),term:double(by name),t:double(by name))
{
     ans:integer;
     ans := 0;
     term := first;
     while (term  <= last) do
        ans := ans + t;
        term := term + incr;
     endwhile;
     return ans;
}

a. What is returned by the call compute(1, 10, 1, J, A[J])?

b. What is returned by the call compute(1,5,1, J, 1/A[J])?

c. Using your knowledge of how compute() works, can you write
a procedure that calculates the maximun value from a set of values
obtained by evaluating some expression containing a variable that
ranges from a given lower bound to an upper bound with a given step
size? You can assume the values are integers.

#4. Write your own example for which pass by value-result and
pass by reference have observably different effects. You need to make up 
your own example, different from any in our lecture notes.