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 is a special Rogue Wave header file that includes with a
suffix that depends on your compiler.
//3 This line invokes the macro declare, which is defined in the header file
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 , 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.