_ISLOWER
ctn->ctype |= _ISLOWER;
if (ctn->ctype & (_ISUPPER |_ISLOWER))
ctn->ctype |= (_ISLOWER | _ISALPHA | _ISGRAPH | _ISPRINT);
#define _CTYPE_L _ISLOWER /* Lower */
DEFN_ISTYPE(lower, _ISLOWER)