/*
 *  call-seq:
 *     rxp.fixed_encoding?   => true or false
 *
 *  Returns false if rxp is applicable to
 *  a string with any ASCII compatible encoding.
 *  Returns true otherwise.
 *
 *      r = /a/
 *      r.fixed_encoding?                               #=> false
 *      r =~ "\u{6666} a"                               #=> 2
 *      r =~ "\xa1\xa2 a".force_encoding("euc-jp")      #=> 2
 *      r =~ "abc".force_encoding("euc-jp")             #=> 0
 *
 *      r = /a/u
 *      r.fixed_encoding?                               #=> true
 *      r.encoding                                      #=> #<Encoding:UTF-8>
 *      r =~ "\u{6666} a"                               #=> 2
 *      r =~ "\xa1\xa2".force_encoding("euc-jp")        #=> ArgumentError
 *      r =~ "abc".force_encoding("euc-jp")             #=> 0
 *
 *      r = /\u{6666}/
 *      r.fixed_encoding?                               #=> true
 *      r.encoding                                      #=> #<Encoding:UTF-8>
 *      r =~ "\u{6666} a"                               #=> 0
 *      r =~ "\xa1\xa2".force_encoding("euc-jp")        #=> ArgumentError
 *      r =~ "abc".force_encoding("euc-jp")             #=> nil
 */

static VALUE
rb_reg_fixed_encoding_p(VALUE re)
{
    if (FL_TEST(re, KCODE_FIXED))
        return Qtrue;
    else
        return Qfalse;
}