[]=

/*
 *  call-seq:
 *     struct[symbol] = obj    => obj
 *     struct[fixnum] = obj    => obj
 *  
 *  Attribute Assignment---Assigns to the instance variable named by
 *  <i>symbol</i> or <i>fixnum</i> the value <i>obj</i> and
 *  returns it. Will raise a <code>NameError</code> if the named
 *  variable does not exist, or an <code>IndexError</code> if the index
 *  is out of range.
 *     
 *     Customer = Struct.new(:name, :address, :zip)
 *     joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
 *     
 *     joe["name"] = "Luke"
 *     joe[:zip]   = "90210"
 *     
 *     joe.name   #=> "Luke"
 *     joe.zip    #=> "90210"
 */

VALUE
rb_struct_aset(s, idx, val)
    VALUE s, idx, val;
{
    long i;

    if (TYPE(idx) == T_STRING || TYPE(idx) == T_SYMBOL) {
        return rb_struct_aset_id(s, rb_to_id(idx), val);
    }

    i = NUM2LONG(idx);
    if (i < 0) i = RSTRUCT(s)->len + i;
    if (i < 0) {
        rb_raise(rb_eIndexError, "offset %ld too small for struct(size:%ld)",
                 i, RSTRUCT(s)->len);
    }
    if (RSTRUCT(s)->len <= i) {
        rb_raise(rb_eIndexError, "offset %ld too large for struct(size:%ld)",
                 i, RSTRUCT(s)->len);
    }
    rb_struct_modify(s);
    return RSTRUCT(s)->ptr[i] = val;
}