unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, expr, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
  private
    function GetFuncValue(const FuncName, FuncParams: string): Double;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  yacc: TYacc;
  Lex: TLex;
  B: SmallInt;
begin
  if Trim(Edit1.Text) = '' then Exit;
  yacc := TYacc.Create;
  Lex := TLex.Create;
  yacc.ylex := Lex;

  Lex.llib.yyinput := Edit1.Text + ';';
  yacc.GetFuncValue := GetFuncValue;
    if yacc.yyparse = 0 then
      Memo1.Lines.Add(Lex.llib.yyoutput);
end;

function TForm1.GetFuncValue(const FuncName, FuncParams: string): Double;
begin
  if (FuncName = 'TESTFUNC') then
    Result := sqr(StrToFloat(FuncParams));
end;

end.