pragma solidity ^0.4.0;
contract C{
    uint[] public data1;
    uint[] public data2;
    function appendOne() public {
        append(data1);
    }
    function appendTwo() public {
        append(data2);
    }
    function append(uint[] storage d) internal{
        d.push(1);
    }
    function length1() public view returns(uint){
        return data1.length;
    }
    function length2() public view returns(uint){
        return data2.length;
    }
    //TypeError: Member "push" is not available in uint256[] memory outside of storage.
    // function add(uint[] d) public {
    //     d.push(27);
    // }
    //Location has to be memory for publicly visible functions (remove the "storage" keyword).
    // 有两种选择，防止随意的修改状态，方法不能对外公开
    // 第一是可以把storage去掉，但去掉以后不能push
    // 第二是保留storage，把public改为internal
    // function add(uint[] storage d) public {
    //     d.push(27);
    // }
    function add(uint[] storage d) internal {
        d.push(27);
    }
}