MODULE compress; (*DEE 2014-08-06/2015-12-02*)
  (* Software Tools in Pascal, exercise 2-9. *)
  FROM ST IMPORT getc, putc;
  FROM STchars IMPORT ENDFILE, character;
  FROM CE IMPORT putrep, WARNING;

  (* compress: compress standard input. See expand. *)
  PROCEDURE compress;
    VAR
      c, lastc: character;
      n: INTEGER;
  BEGIN
    n := 1;
    lastc := getc(lastc);
    WHILE (lastc # ENDFILE) DO
      IF (getc(c) = ENDFILE) THEN
        IF (n > 1) OR (lastc = WARNING) THEN
          putrep(n, lastc)
        ELSE
          putc(lastc)
        END
      ELSIF (c = lastc) THEN
        INC(n)
      ELSIF (n > 1) OR (lastc = WARNING) THEN
        putrep(n, lastc); n := 1
      ELSE
        putc(lastc)
      END;
      lastc := c
    END
  END compress;

BEGIN compress
END compress.