CSc 17 Test 1  Wednesday 8 October 1997     ANSWERS

  1.  (15 pts)  This is a true-false question.  After each expression
         state whether the expression evaluates to true or to false.
       ( 3/2 == (2/3+1))                           TRUE
       (('a'>'b') || ( ('b'-'a')>0 ) )             TRUE
       (('a'+int(true))>'a')                       TRUE
       ((3/2.0) == (2/3.0 + 1))                    FALSE
       ((17%3+1) > (3%17))                         FALSE
       ( ((2>3)==(3>2)) == ( (4-3>0)==(10<4) ) )   TRUE
       ('0' == int('0') )                          TRUE
       ( 'T'-'t' + 'q'-'Q' >0)                     FALSE
       ('t'-'r'+true == 3)                         TRUE
       ( !(4==5) == !(7>5) );                      FALSE
  2.  (10 pts)  Given the function and variable declarations below, state
         what output is generated by the code below the dashed line
         void a(int &x,int &y,int z)
            { if (x==y) {if (x>z) x++; z++;} else {x++; y++;}
              cout << " "<< x <<" "<< y <<" "<< z;
              return; }
     -----------------------------------------------------------------
               int x,y,z;

               x=4; y=3; z=5;
               a(x,y,z);                             5 4 5
               cout <<" "<< x << " " << z;           5 5
               x=4; y=3;
               a(x,x,y);                             5 5 4
               cout <<" "<< x << " " << y;           5 3
  3.  (15 pts) Find 10 syntax errors in the following code:
       #include <iosteam.h>      << iostream.h misspelled
       a(int b);
       int c                     << missing semi-colon
       main                      << missing parentheses
        {float d;
         cin << d;               << cin does not understand
         if a(d,8)               << missing parentheses << too many parameters
            d=-d                 << missing semi-colon
         cout << d;}             << missing return

       int a(int b)
        {b=d;                    << d is inaccessible to a
         return;}                << must return a value



  4.  (30 pts)  Given the declaration   int list[20],count  write a
     function called 'powers' such that the call powers(list,count) lists,
     in reverse order of entry in list, three vertical columns, the first
     column consisting of the values (in reverse order) in the list, the
     second column consisting of the squares of the values, and the third
     column consisting of the cubes of the values. The function assumes that
     count stores the number of entries in the array.  Thus, if count=3,
     and the first three entries are 2, 8 3, then the output would look
     something like

               3    9   27
               8   64  512
               2    4    8

          void powers(int list[],int count)
           { int k;
             while (count>0)
              {count--;
               cout << list[count] << "     " << list[count]*list[count]
                    << "          " << list[count]*list[count]*list[count]
                    << endl;
               }
             return;
            }
  5.  (30 pts)  Write a function called large such that for floats x and y
         large(x,y)  will either (a) swap x and y if x is larger than y and
         return a value of true (b) leave x and y alone if x is not
         larger than y and return a value of false.  Thus, if we have
         float x=5,y=3 then the call large(x,y) will return a value of true
         and x will be 3 and y will be 5.  If we have float x=13,y=15 then
         the call large(x,y) will return false and x will still be 13 and y
         will still be 15.

                 bool large(float &x, float &y)
                  { float temp;
                    if (x>y)
                     {temp=x;
                      x=y;
                      y=temp;
                      return true;
                     }
                    else
                     return false;
                  }