MODULE detab; (*DEE 2014-01-20/2015-11-30/2015-12-01*)
  (*Software Tools in Pascal, exercises 1-6 and 1-7a.*)
  FROM ST IMPORT getc, putc;
  FROM STchars IMPORT character, BACKSPACE, BLANK, ENDFILE, NEWLINE, TAB;
  FROM Tabs IMPORT setTabPos;

  (* detab: convert tabs to equivalent number of blanks. *)
  PROCEDURE detab;
    VAR
      c: character;
      col: INTEGER;
  BEGIN col := 1;
    WHILE (getc(c) # ENDFILE) DO
      IF (c = TAB) THEN
        REPEAT
          putc(BLANK);
          INC(col)
        UNTIL (setTabPos(col))
      ELSIF (c = NEWLINE) THEN
        putc(NEWLINE);
        col := 1
      ELSIF (c = BACKSPACE) THEN
        putc(c);
        IF (col >= 1) THEN
          DEC(col)
        END
      ELSE
        putc(c);
        INC(col)
      END;
    END
  END detab;

BEGIN detab
END detab.