old/PAS/Plotting/WRITEFUN.PAS

Uses CRT,GRAPH,Strcalc;
Const
  Eps = 0.001;
  Del = 5000;
  Frames = 1000;
Var
 Fn:string;
  LeftGr  : real;
  RightGr : real;

Procedure InitG;
Var
  grDriver: Integer;
  grMode: Integer;
  i : integer;
Begin
  grDriver := Detect;
  InitGraph(grDriver, grMode,'');
{  SetWriteMode(XORPut);}
  SetFillStyle(XHatchFill,Green);
  Bar(0,0,GetMaxX,GetMaxY);
  SetFillStyle(SolidFill,Black);
  Bar(100,50,540,450);
  SetColor(Red);
  Line(100,250,540,250);
End;{InitG}
{--------------------------------}
Function Func(x: real): real;
Var
 ret: real;
Begin
  ret := StrFunc(fn,x);
  Func := ret;
End;
{-----------------------------}
Procedure WriteGraph(l,r:real;Color:Integer);
Var
  x,y : Integer;
  razmx,razmy,max,min: real;
Begin
  Razmx := r-l;
  SetColor(Color);
  min := maxint;
  min := -maxint;
  for x := 1 to Frames do
    begin
      y := round(Func(l+(x/Frames)*razmx)*10);
      if y < min then min := y;
      if y > max then max := y
    end;

  razmy := max-min;

  MoveTo(100,250-Round(-200+((Func(l)-min)/razmy*400)));
  for x := 1 to Frames do
    begin
      Y:=Round(-200+((Func(l+(x/Frames)*razmx)-min)/razmy*400));
      LineTo(100+round(x/Frames*440),250-y);
    end;
End;{WriteGraph}
{---------------------------------}
Begin
  Write('Enter function: ');
  ReadLn(fn);
  Read(LeftGr,RightGr);
  InitG;
  WriteGraph(leftGr,RightGR,Blue);
  ReadKey;
  CloseGraph;
End.