HP 3000 Manuals

HP Pascal/iX Reference Manual

Pointer Types 

Pointers 

A pointer is a data type that may reference any type, including type
FILE. A pointer references a dynamically allocated variable on the heap.
The pointer type consists of the caret (^) and a type identifier.  The @
symbol may replace the caret.

The type appearing after the caret need not be previously defined.  This
is an exception to the general rule that HP Pascal identifiers are first
defined and then used.  However, the identifier after the caret must be
defined within the same declaration part.

A type identifier used in a pointer type declaration in an EXPORT section
need not be defined until the IMPLEMENT section.  A pointer declared in
this manner cannot be dereferenced in modules that IMPORT the pointer
type. 

The pointer value NIL belongs to every pointer type.  NIL points to no
variable on the heap.  For more information, refer to the section on NIL
in this chapter.

Syntax 

     Pointer_type:


            

Permissible Operators 

 assignment      :=

 equality        =, <>

Standard Procedures 

 pointer parameters -    new
                         dispose
                         mark
                         release

Example 

     TYPE
        ptr1   = ^rec1;
        ptr2   = ^rec2;
        rec1   = RECORD
                    f1, f2: integer;
                    link:   ptr2;
                 END;
        rec2   = RECORD
                    f1, f2: real;
                    link:   ptr1;
                 END;

MPE/iX 5.0 Documentation