Homework #32

Polymorphism - (20 minutes)
This problem is not from your textbook.

In Lecture 31, we talked about polymorphism.  Label each of the following C++ examples as using ad hoc or universal polymorphism (specify overloading, coercion, inclusion, or parametric) and explain your decision. If you're not sure exactly how C++ implements a particular form of polymorphism (whether it's overloaded or coerced, for example), take your best guess and explain it.

1. double sqrt( double );
   float  f = 1.0f;   //The 'f' in 1.0f means to interpret 1.0 as a float and not a double
   double d = 1.0;    //The 1.0 here will be interpreted as a double
   
   f += sqrt( f );
   d += sqrt( d );

   There are two uses of polymorphism in the above code.

2. class A { ...};
   class B: public A { ... };
   class C: public A { ... };
   
   A a;
   B b;
   C c;
   A array_of_A[10];
   
   array_of_A[0] = a;
   array_of_A[1] = b;
   array_of_A[2] = c;

3. #include <vector.h>
   ...
   vector<int>   v(10, 0);

4. char c  = 'A';
   int  i  = 10;
   int  *p = &i;
   
   (p++) + (i++) + (c++);

   There are also two polymorphic operators in this last example. (For this one, consider polymorphic operations in the last expression, not in the three declarations.)

   Be careful with this one--the last line evaluates to a pointer.

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Last updated at 9:53 am on Friday, August 27, 2004.