compress Subroutine

   SUBROUTINE compress(string, full)
      !! Eliminate multiple space characters in a string.
      !! If full is .TRUE., then all spaces are eliminated.

      CHARACTER(LEN=*), INTENT(INOUT)                    :: string
      LOGICAL, INTENT(IN), OPTIONAL                      :: full

      CHARACTER                                          :: tmp
      INTEGER                                            :: i, z
      LOGICAL                                            :: remove_all

      IF (PRESENT(full)) THEN
         remove_all = full
      ELSE
         remove_all = .FALSE.
      END IF

      z = 1

      DO i = 1, LEN_TRIM(string)
         IF ((z == 1) .OR. remove_all) THEN
            IF (string(i:i) /= " ") THEN
               tmp = string(i:i)
               string(z:z) = tmp
               z = z + 1
            END IF
         ELSE
            IF ((string(i:i) /= " ") .OR. (string(z - 1:z - 1) /= " ")) THEN
               tmp = string(i:i)
               string(z:z) = tmp
               z = z + 1
            END IF
         END IF
      END DO

      string(z:) = ""

   END SUBROUTINE compress