dos_compilers/Borland Turbo Pascal v6/DOCDEMOS/LISTDEMO.PAS

{ Turbo List }
{ Copyright (c) 1989,90 by Borland International, Inc. }

program ListDemo;
{ From Chapter 4 the Turbo Pascal 6.0 User's Guide.
  Dynamic objects & destructors.

  If you are running this program in the IDE, be sure to enable
  the full graphics save option when you load TURBO.EXE:

    turbo -g

  This ensures that the IDE fully swaps video RAM and keeps
  "dustclouds" from appearing on the user screen when in
  graphics mode. You can enable this option permanently
  via the Options|Environment|Startup dialog.

  This program uses the Graph unit and its .BGI driver files to
  display graphics on your system. The "PathToDrivers"
  constant defined below is set to \TP\BGI, which is the default
  location of the BGI files as installed by the INSTALL program.
  If you have installed these files in a different location, make
  sure the .BGI file for your system (EGAVGA.BGI, etc.) is in the
  current directory or modify the "PathToDrivers" constant
  accordingly.
}

uses Graph, Figures;

const
  PathToDrivers = '\TP\BGI';  { Default location of *.BGI files }

type
  ArcPtr = ^Arc;
  Arc = object(Circle)
    StartAngle, EndAngle: Integer;
    constructor Init(InitX, InitY: Integer; InitRadius: Integer;
      InitStartAngle, InitEndAngle: Integer);
    procedure Show; virtual;
    procedure Hide; virtual;
  end;

  NodePtr = ^Node;
  Node = record
    Item: PointPtr;
    Next: NodePtr;
  end;

  ListPtr = ^List;
  List = object
    Nodes: NodePtr;
    constructor Init;
    destructor Done; virtual;
    procedure Add(Item: PointPtr);
    procedure Report;
  end;

var
  GraphDriver: Integer;
  GraphMode: Integer;
  Temp: String;
  AList: List;
  PArc: ArcPtr;
  PCircle: CirclePtr;
  RootNode: NodePtr;


{--------------------------------------------------------}
{ Procedures that are not methods:                       }
{--------------------------------------------------------}

procedure OutTextLn(TheText: String);
begin
  OutText(TheText);
  MoveTo(0, GetY+12);
end;

procedure HeapStatus(StatusMessage: String);
begin
  Str(MemAvail: 6, Temp);
  OutTextLn(StatusMessage+Temp);
end;


{--------------------------------------------------------}
{ Arc's method implementations:                          }
{--------------------------------------------------------}

constructor Arc.Init(InitX, InitY: Integer; InitRadius: Integer;
  InitStartAngle, InitEndAngle: Integer);
begin
  Circle.Init(InitX, InitY, InitRadius);
  StartAngle := InitStartAngle;
  EndAngle := InitEndAngle;
end;

procedure Arc.Show;
begin
  Visible := True;
  Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
end;

procedure Arc.Hide;
var
  TempColor: Word;
begin
  TempColor := Graph.GetColor;
  Graph.SetColor(GetBkColor);
  Visible := False;
  Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
  SetColor(TempColor);
end;


{--------------------------------------------------------}
{ List's method implementations:                         }
{--------------------------------------------------------}

constructor List.Init;
begin
  Nodes := nil;
end;

destructor List.Done;
var
  N: NodePtr;
begin
  while Nodes <> nil do
  begin
    N := Nodes;
    Nodes := N^.Next;
    Dispose(N^.Item, Done);
    Dispose(N);
  end;
end;

procedure List.Add(Item: PointPtr);
var
  N: NodePtr;
begin
  New(N);
  N^.Item := Item;
  N^.Next := Nodes;
  Nodes := N;
end;

procedure List.Report;
var
  Current: NodePtr;
begin
  Current := Nodes;
  while Current <> nil do
  begin
    Str(Current^.Item^.GetX:3, Temp);
    OutTextLn('X = ' + Temp);
    Str(Current^.Item^.GetY:3, Temp);
    OutTextLn('Y = ' + Temp);
    Current := Current^.Next;
  end;
end;


{--------------------------------------------------------}
{ Main program:                                          }
{--------------------------------------------------------}

begin
  { Let BGI determine which board you're using: }
  DetectGraph(GraphDriver, GraphMode);
  InitGraph(GraphDriver, GraphMode, PathToDrivers);
  if GraphResult <> GrOK then
  begin
    Writeln(GraphErrorMsg(GraphDriver));
    if GraphDriver = grFileNotFound then
    begin
      Writeln('in ', PathToDrivers,
        '. Modify this program''s "PathToDrivers"');
      Writeln('constant to specify the actual location of this file.');
      Writeln;
    end;
    Writeln('Press Enter...');
    Readln;
    Halt(1);
  end;

  HeapStatus('Heap space before list is allocated: ');

  { Create a list }
  AList.Init;

  { Now create and add several figures to it in one operation }
  AList.Add(New(ArcPtr, Init(151, 82, 25, 200, 330)));
  AList.Add(New(CirclePtr, Init(400, 100, 40)));
  AList.Add(New(CirclePtr, Init(305, 136, 5)));

  { Traverse the list and display X,Y of the list's figures }
  AList.Report;

  HeapStatus('Heap space after list is allocated ');

  { Deallocate the whole list with one destructor call }
  AList.Done;

  HeapStatus('Heap space after list is cleaned up: ');

  OutText('Press Enter to end program: ');
  Readln;

  CloseGraph;
end.