Programme analyseur lexical

bonsoir
svp qui peux m'aider pour rectifier mes erreurs voila mon code source:
program tp;
var
iposcurrent,lgchaine:integer;
Result:string;
Montexte:string ;

function IsDigit:Boolean;
begin
 if (iPosCurrent<=LgChaine) and (MonTexte[iPosCurrent] in ['0'..'9']) do ;
result:=true then
result:=false;
end;
///////////////////////////////////////////////////////////////////////////////
function IsAlpha:boolean;
begin
  Result:=(iPosCurrent<=LgChaine) and (UpCase(MonTexte[iPosCurrent]) in ['A'..'Z','_']);
end;
///////////////////////////////////////////////////////////////////////////////
function IsPonctuation : boolean;
begin
  Result:=(iPosCurrent<=LgChaine) and (MonTexte[iPosCurrent] in ['(',';',':',')','[',']','.']);
end;
///////////////////////////////////////////////////////////////////////////////
 
Function IsOperateur : boolean;
begin
 
  Result:=(iPosCurrent<=LgChaine) and (UpCase(MonTexte[iPosCurrent]) in ['+','-','*','/','<','<=','>=','<>','='];


function ExtractMot : String;
begin
  Result:=copy(Line,iPosStart,IPosEnd);
end;
///////////////////////////////////////////////////////////////////////////////
function GetDigit : string;
var
  i:integer;
begin
  IPosStart :=iPosCurrent;
  while IsDigit do
     inc(iPosCurrent);
  IPosEnd :=iPosCurrent -1;  
  Result :=ExtractMot;
end;
///////////////////////////////////////////////////////////////////////////////
function GetAlpha : string;
var
  i:integer;
begin
  IPosStart :=iPosCurrent;
  while IsAlpha do
     inc(iPosCurrent);
  IPosEnd :=iPosCurrent -1;  
  Result :=ExtractMot;
end;
///////////////////////////////////////////////////////////////////////////////
function GetPonctuation := string;
 var
  i:integer;
begin
  IPosStart :=iPosCurrent;
  while IsPonctuation do
     inc(iPosCurrent);
  IPosEnd :=iPosCurrent -1;  
  Result :=ExtractMot;
end;

function GetOperateur := string;
 var
  i:integer;
begin
  IPosStart :=iPosCurrent;
  while IsOperqteur do
     inc(iPosCurrent);
  IPosEnd :=iPosCurrent -1;  
  Result :=ExtractMot;
end;


begin

 LgChaine := length(MonTexte);

 iPosCurrent := 1;

 while (iPosCurrent <=LgChaine do

 begin
      ...
      inc(iPosCurrent);
  end;

merci

EDIT: Ajout de la coloration syntaxique.