M2compiler-V3/compiler/tests/t_emptychar.mod

MODULE TEmptyChar;
// ISO: the empty string literal has length 0 and is compatible with
// CHAR, where its value is the terminator.  It also stays a string for
// CHAR arrays (t_strempty covers that side). Exit 42.
VAR ExitCode : INTEGER;
VAR ch : CHAR;
VAR s : ARRAY [0..3] OF CHAR;
VAR i : INTEGER;
PROCEDURE IsNul (c: CHAR) : BOOLEAN;
BEGIN
  RETURN c = ""
END IsNul;
PROCEDURE Nul () : CHAR;
BEGIN
  RETURN ""
END Nul;
BEGIN
  i := 0;
  ch := "";
  IF (ch = "") AND IsNul(ch) AND (Nul() = "") THEN i := i + 1 END;
  CASE ch OF
    "" : i := i + 10
  | 'x' : i := i + 100
  ELSE i := i + 200
  END;
  FOR ch := "" TO CHR(2) DO i := i + 1 END;
  (* 1 + 10 + 3 (nul, 1, 2) = 14; +28 = 42 *)
  s := "";
  IF (i = 14) AND (s[0] = CHR(0)) THEN ExitCode := 42 ELSE ExitCode := i END
END TEmptyChar.