PLVstk: Stack Manager

The PLVstk (PL/Vision STacK manager) package is a generic manager for both first-in-first-out (FIFO) and last-in-last-out (LIFO) stacks; it is built on PLVlst. See the companion disk for details.

Package constants

• defstk CONSTANT VARCHAR2(5) := 'stack';
• The name of the default stack.
• lifo CONSTANT VARCHAR2(4) := 'LIFO';
• Indicates that you are working with a last-in-first-out stack. Used in calls to pop.
• fifo CONSTANT VARCHAR2(4) := 'FIFO';
• Indicates that you are working with a first-in-first-out stack. Used in calls to pop.

5.24.2 Creating and destroying stacks

• PROCEDURE make
• (stack_in IN VARCHAR2 := defstk,
• overwrite_in IN BOOLEAN := TRUE);
• Allocates storage for a stack of up to 1,000 items with the specified name. By default, if the stack already exists it will be reinitialized to an empty stack.
• PROCEDURE destroy (stack_in IN VARCHAR2 := defstk);
• Releases all memory associated with this stack.

Modifying stack contents

• PROCEDURE push
• (item_in IN VARCHAR2, stack_in IN VARCHAR2 := defstk);
• Pushes an item onto the specified stack.
• PROCEDURE pop
• (value_out IN OUT VARCHAR2,
• stack_in IN VARCHAR2 := defstk,
• stack_type_in IN VARCHAR2 := lifo);
• Pops an item off the top (LIFO) or bottom (FIFO) of the stack.

Analyzing stack contents

• FUNCTION nitems (stack_in IN VARCHAR2 := defstk)
• RETURN INTEGER;
• Returns the number of items currently in the stack.
• FUNCTION itemin (stack_in IN VARCHAR2, item_in IN VARCHAR2)
• RETURN BOOLEAN;
• Returns TRUE if the specified item is found in the stack.

5.24.5 Tracing Stack Activity

• PROCEDURE show
• (stack_in IN VARCHAR2 := defstk,
• show_contents_in IN BOOLEAN := FALSE);
• Requests that pre-action status of stack be displayed for the specified stack (or all).
• PROCEDURE noshow;
• Turns off display of pre-action status.
• FUNCTION showing RETURN BOOLEAN;
• Returns TRUE if showing pre-action status.
• PROCEDURE verify
• (stack_in IN VARCHAR2 := defstk,
• show_contents_in IN BOOLEAN := FALSE);
• Requests that post-action status of stack be displayed for the specified stack (or all).
• PROCEDURE noverify;
• Turns off display of post-action status.
• FUNCTION verifying RETURN BOOLEAN;
• Returns TRUE if showing post-action status.