HP Integrity NonStop J-Series - Manual (Page 143)

Each line of the program is detailed below.
//1 This #include defines the preprocessor macro RWGStackdeclare(type). This macro is
an elaborate and ugly-looking thing that continues for many lines and describes how a
generic stack of objects of type type should behave. Mostly, the macro serves as a
restricted interface to the underlying implementation, which is a singly-linked list,
class
RWSlist . It is restricted because it can use only those member functions of
RWSlist appropriate to stacks, and insert into the stack only items of type type.
//2 <rw/rstream.h> is a special Rogue Wave header file that includes <iostream.h> with a
suffix that depends on your compiler.
//3 This line invokes the macro declare, which is defined in the header file <generic.h>
supplied with your compiler. If called with arguments declare(Class, type), it calls the
macro Classdeclare with argument type. In this case, the macro RWGStackdeclare,
defined in <rw/gstack.h>, will be called with argument int.
In other words, the result of calling the declare(RWGStack, int) macro is to create a
new class especially for your program. For all practical purposes, its name is
RWGStack(int) , a stack of pointers to ints.
//4 At this line an instance gs of the new class RWGStack(int) is created.
//5 - //8 Four ints are created off the heap and inserted into the stack. After statement 8
executes, a pointer to the int 4 will be at the top of the stack, and a pointer to the int 1
at the bottom.
//9 The member function entries() of class RWGStack(int) is called to verify how many
items are on the stack.
//10 A pointer to an int is declared and defined.
//11 The stack is popped until empty. The member function pop() will return and remove a
pointer to the item on the top of the stack. If there are no more items on the stack it
will return zero, causing the while loop to terminate.
//12 Each item is dereferenced and printed.