solidity定长数组和动态数组

uint[5] fixedArr = [1,2,3,4,5];

// 通过for循环计算数组值的总和
function sum() public view returns (uint) {
    uint total = 0;
    for(uint i = 0; i < fixedArr.length; i++) {
        total += fixedArr[i];
    }
    return total;
}

TypeError: Expression has to be an lvalue.
fixedArr.length = len;

function updateValue(uint index,uint value) public {
    fixedArr[index] = value;
}

uint[] unfixedArr = [1,2,3,4,5];
// 或
uint[] unfixedArr;

// 通过for循环计算数组值的总和
function sum() public view returns (uint) {
    uint total = 0;
    for(uint i = 0; i < unfixedArr.length; i++) {
        total += unfixedArr[i];
    }
    return total;
}

unfixedArr.push(1);
或
unfixedArr = new uint[](1); 
unfixedArr[0] = 0;

unfixedArr.length = len;