How to implement the RPos

Problem/Question/Abstract:

Sometime Pos is not enough, because you need to find the position of the first character of a sub string in a string from the end of that string. There's the solution.

Answer:

function RPos(Substr: string; S: string): Integer;
var
  i: Integer;
begin
  Result := 0;
  if ((Length(S) > 0) and (Length(Substr) > 0)) then
    if (Length(S) >= Length(Substr)) then
      for i:= (Length(S) - Length(Substr)) downto 1 do
        if (Copy(S, i, Length(Substr)) = Substr) then
        begin
          Result := i;
          Exit;
        end;
end;