/* 
 *  call-seq:
 *     array[index]         = obj                     ->  obj
 *     array[start, length] = obj or an_array or nil  ->  obj or an_array or nil
 *     array[range]         = obj or an_array or nil  ->  obj or an_array or nil
 *
 *  Element Assignment---Sets the element at _index_,
 *  or replaces a subarray starting at _start_ and
 *  continuing for _length_ elements, or replaces a subarray
 *  specified by _range_.  If indices are greater than
 *  the current capacity of the array, the array grows
 *  automatically. A negative indices will count backward
 *  from the end of the array. Inserts elements if _length_ is
 *  zero. If +nil+ is used in the second and third form,
 *  deletes elements from _self_. An +IndexError+ is raised if a
 *  negative index points past the beginning of the array. See also
 *  <code>Array#push</code>, and <code>Array#unshift</code>.
 * 
 *     a = Array.new
 *     a[4] = "4";                 #=> [nil, nil, nil, nil, "4"]
 *     a[0, 3] = [ 'a', 'b', 'c' ] #=> ["a", "b", "c", nil, "4"]
 *     a[1..2] = [ 1, 2 ]          #=> ["a", 1, 2, nil, "4"]
 *     a[0, 2] = "?"               #=> ["?", 2, nil, "4"]
 *     a[0..2] = "A"               #=> ["A", "4"]
 *     a[-1]   = "Z"               #=> ["A", "Z"]
 *     a[1..-1] = nil              #=> ["A"]
 */

static VALUE
rb_ary_aset(argc, argv, ary)
    int argc;
    VALUE *argv;
    VALUE ary;
{
    long offset, beg, len;

    if (argc == 3) {
        if (SYMBOL_P(argv[0])) {
            rb_raise(rb_eTypeError, "Symbol as array index");
        }
        if (SYMBOL_P(argv[1])) {
            rb_raise(rb_eTypeError, "Symbol as subarray length");
        }
        rb_ary_splice(ary, NUM2LONG(argv[0]), NUM2LONG(argv[1]), argv[2]);
        return argv[2];
    }
    if (argc != 2) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 2)", argc);
    }
    if (FIXNUM_P(argv[0])) {
        offset = FIX2LONG(argv[0]);
        goto fixnum;
    }
    if (SYMBOL_P(argv[0])) {
        rb_raise(rb_eTypeError, "Symbol as array index");
    }
    if (rb_range_beg_len(argv[0], &beg, &len, RARRAY(ary)->len, 1)) {
        /* check if idx is Range */
        rb_ary_splice(ary, beg, len, argv[1]);
        return argv[1];
    }

    offset = NUM2LONG(argv[0]);
fixnum:
    rb_ary_store(ary, offset, argv[1]);
    return argv[1];
}