Arrays copy memory in Solidity

Question

I have this simple code:

function restart() public returns (uint256[] ) {
    uint256[] memory result = new uint256[](5);
    result[0] = 10;
    uint256[] memory result1 = new uint256[](5);
    result1 = result;
    result1[1] = 20;
    return result;
}

The result final value is : {10,20}. But I wanted for it to just be {10}. Is there a way to copy an array without being a pointer? I basically just want to create a "local" copy of result. thank you

Answer 1

You can copy element by element

function restart() public returns (uint256[] ) {
    uint256[] memory result = new uint256[](5);
    result[0] = 10;
    uint256[] memory result1 = new uint256[](5);

    for (uint i=0; i < 5; i += 1) {
        result1[i] = result[i];
    }

    result1[1] = 20;
    return result;
}

Answer 2

Well what you are doing is so strange for me. i think if you want to do this you can take out the result variable from the function memory and put it outside the function in storage.

uint256[] public result = new uint256[](5);
   
    function restart() public returns (uint256[] ) { 
        result[0] = 10; 
        uint256[] memory result1 = new uint256[](5); 
        result1 = result; 
        result1[1] = 20; 
        return result; 
        
    }

I think the reason for this is that when you make 2 memory variables in a function and assign one to another they both point out to the same location because they are both has been made inside a function and they're both local. So you can't do such a thing.

Solidity Docs

Assignments from memory to memory only create references. This means that changes to one memory variable are also visible in all other memory variables that refer to the same data.

I still wait for someone to approve or reject what i have said.