rindex

/*
 *  call-seq:
 *     array.rindex(obj)    ->  int or nil
 *  
 *  Returns the index of the last object in <i>array</i>
 *  <code>==</code> to <i>obj</i>. If a block is given instead of an
 *  argument, returns first object for which <em>block</em> is
 *  true. Returns <code>nil</code> if no match is found.
 *     
 *     a = [ "a", "b", "b", "b", "c" ]
 *     a.rindex("b")        #=> 3
 *     a.rindex("z")        #=> nil
 *     a.rindex{|x|x=="b"}  #=> 3
 */

static VALUE
rb_ary_rindex(argc, argv, ary)
    int argc;
    VALUE *argv;
    VALUE ary;
{
    VALUE val;
    long i = RARRAY(ary)->len;

    if (argc == 0) {
        RETURN_ENUMERATOR(ary, 0, 0);
        while (i--) {
            if (RTEST(rb_yield(RARRAY(ary)->ptr[i])))
                return LONG2NUM(i);
            if (i > RARRAY(ary)->len) {
                i = RARRAY(ary)->len;
            }
        }
        return Qnil;
    }
    rb_scan_args(argc, argv, "01", &val);
    while (i--) {
        if (rb_equal(RARRAY(ary)->ptr[i], val))
            return LONG2NUM(i);
        if (i > RARRAY(ary)->len) {
            i = RARRAY(ary)->len;
        }
    }
    return Qnil;
}