array.c:1504
VALUE
rb_ary_clear(ary)
    VALUE ary;
{
    rb_ary_modify(ary);
    RARRAY(ary)->len = 0;
    if (ARY_DEFAULT_SIZE * 2 < RARRAY(ary)->aux.capa) {
	REALLOC_N(RARRAY(ary)->ptr, VALUE, ARY_DEFAULT_SIZE * 2);
	RARRAY(ary)->aux.capa = ARY_DEFAULT_SIZE * 2;
    }
    return ary;
}
