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------------------------------------------------------------------------------
-- --
-- DISPLAY_SOURCE COMPONENTS --
-- --
-- S T A C K S --
-- --
-- B o d y --
-- --
-- Copyright (c) 1995-2002, Free Software Foundation, Inc. --
-- --
-- Display_Source is free software; you can redistribute it and/or modify it--
-- under terms of the GNU General Public License as published by the Free --
-- Software Foundation; either version 2, or (at your option) any later --
-- version. Display_Source is distributed in the hope that it will be use- --
-- ful, but WITHOUT ANY WARRANTY; without even the implied warranty of MER- --
-- CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General --
-- Public License for more details. You should have received a copy of the --
-- GNU General Public License distributed with GNAT; see file COPYING. If --
-- not, write to the Free Software Foundation, 59 Temple Place Suite 330, --
-- Boston, MA 02111-1307, USA. --
-- --
-- Display_Source is distributed as a part of the ASIS implementation for --
-- GNAT (ASIS-for-GNAT). --
-- --
-- The original version of Display_Source has been developed by --
-- Jean-Charles Marteau and Serge Reboul, ENSIMAG High School Graduates --
-- (Computer sciences) Grenoble, France in Sema Group Grenoble, France. --
-- --
-- Display_Source is now maintained by Ada Core Technologies Inc --
-- (http://www.gnat.com). --
------------------------------------------------------------------------------
-----------------------------------------------------------------
-- This package is part of the ASIS application display_source --
-----------------------------------------------------------------
package body Stacks is
type T_Node is
record
Elem : aliased T_Elem;
Next : Stack;
end record;
-- I don't like allocating new records to get rid
-- of them in the next minute, so there is a record
-- provider here that gets the old ones and give
-- them back when needed. That means unemployment for
-- garbage collectors ... :)
Stock : array (1 .. Initial_Number) of aliased T_Node;
-- He he this is a stock of stack ... :)
Is_Provider_Initialized : Boolean := False;
pragma Unreferenced (Is_Provider_Initialized);
Provider : Stack := Stock (1)'Access;
procedure Init_Provider;
procedure Init_Provider is
begin
for I in 2 .. Initial_Number loop
Stock (I - 1).Next := Stock (I)'Access;
end loop;
Stock (Initial_Number).Next := Empty_Stack;
end Init_Provider;
-- standard functions for a stack :
-- Push puts an Elem on the top of the stack
-- Pop gets the last pushed element of the stack
procedure Push (St : in out Stack; Elem : in T_Elem) is
Neu : Stack := Provider;
-- Well as new is a reserved word, i use neu which is
-- new in valencian, a language spoken in a spanish
-- city on the east coast (east coast of spain ...)
-- Isn't that exotic ?
begin
if Neu = Empty_Stack then
-- Arg ! We got to do it !!!
Neu := new T_Node;
else
Provider := Provider.Next;
end if;
Neu.Elem := Elem;
Neu.Next := St;
St := Neu;
end Push;
procedure Pop (St : in out Stack; Elem : out T_Elem) is
Old : Stack := St;
begin
if St = Empty_Stack then
raise Stack_Error;
end if;
Elem := St.Elem;
St := St.Next;
Old.Next := Provider;
Provider := Old;
end Pop;
-- Upper lets you have access to the first Elem
-- on the top of the stack.
function Upper (St : in Stack) return A_Elem is
begin
if St = Empty_Stack then
return null;
else
return St.Elem'Access;
end if;
end Upper;
function Size_Of_Stack (St : in Stack) return Natural is
Result : Natural := 0;
Current : Stack := St;
begin
while Current /= Empty_Stack loop
Result := Result + 1;
Current := Current.Next;
end loop;
return Result;
end Size_Of_Stack;
function Is_Empty (St : in Stack) return Boolean is
begin
return St = Empty_Stack;
end Is_Empty;
begin
Init_Provider;
end Stacks;
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