Chapter-3/3-3/expand.c
/* validrange:  returns non-zero if c1-c2 is a valid range. */
returns non-zero if c1-c2 is a valid range.
returns non - zero if c1 - c2 is a valid range .
int validrange(char c1, char c2) {
  if (('a' <= c1 && c1 <= 'z') && 
      (c1 <= c2 && c2 <= 'z'))
    return TRUE;
  if (('A' <= c1 && c1 <= 'Z') && 
      (c1 <= c2 && c2 <= 'Z'))
    return TRUE;
  if (('0' <= c1 && c1 <= '9') && 
      (c1 <= c2 && c2 <= '9'))
    return TRUE;
  return FALSE; 
}
int validrange ( char c1 , char c2 ) { if ( ( ' ' <= c1 && c1 <= ' ' ) && ( c1 <= c2 && c2 <= ' ' ) ) return TRUE ; if ( ( ' ' <= c1 && c1 <= ' ' ) && ( c1 <= c2 && c2 <= ' ' ) ) return TRUE ; if ( ( ' ' <= c1 && c1 <= ' ' ) && ( c1 <= c2 && c2 <= ' ' ) ) return TRUE ; return FALSE ; }
validrange:  returns non-zero if c1-c2 is a valid range.
validrange : returns non - zero if c1 - c2 is a valid range .
/* valid range in a-z */ /* valid range in A-Z */ /* valid range in 0-9 */ /* not a valid range */