-- Assignment : Homework due Sept. 21st, 2006
-- Programmer : Daniel Koestler
-- Course     : CS 240
-- Date       : Sept. 20th, 2006
-- Compiler   : gcc with gnat
-- Professor  : Elizabeth Adams
-- Filename   : stack.ads
-- Executable :
-- Version    : 0.2

-- Purpose: To specify the stack data type as discussed in class with its data types and operations

-- Input : none

-- Output : none

-- Modifications: The MAX constant determines the maximum size of a given
--                stack.
--
--  Version 0.2 : An off-by-one error fixed in the type declaration of
--                my array, and a typo fixed in the peek declaration.
package stack is

   MAX : constant Integer := 20;

   type myArray is array (1..MAX) of Integer;

   type stackType is record
      top         : Integer;   -- alternate choice is        top := 0 : Integer;   
      aStack      : myArray;
      MAXDATA     : Integer := MAX;  -- added to original specification 
   end record;


   procedure push ( theStack : in out stackType; -- procedure to put an item on the stack 
                    theValue : in Integer);      -- modifies stack
						  
   procedure pop  ( theStack : in out stackType; -- procedure to pop an item off the stack
                    theValue : out Integer);		 -- modifies stack by removing the top value
						  
   procedure peek ( theStack : in stackType;		 -- procedure to look at top of stack
                    theValue : in out Integer);  -- leaves stack unchanged
						  
   procedure makeEmpty ( theStack : in out stackType ); -- creates an empty stack
																		  -- alters stack by setting top pointer
																		  
   function isFull  ( theStack : in stackType ) return boolean; -- tests the stack for fullness
																					 -- doesn't alter stack
																					 
   function isEmpty ( theStack : in stackType ) return boolean; -- tests the stack for emptiness
																					 -- doesn't alter stack

end stack;