isdigit
#undef isdigit
#define isdigit(c) _bcs_isdigit(c)
#undef isdigit
#define isdigit(c) _bcs_isdigit(c)
#define isdigit(c) (c >= '0' && c <= '9')
#define isdigit(x) ((x) >= '0' && (x) <= '9')
isdigit(int ch)
#define isdigit(c) ((int)((_ctype_tab_ + 1)[(c)] & _CTYPE_D))