Solidity – Understanding the Point of Omitted Function Parameters in Solidity

solidity

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.4.22 <0.9.0;

contract C {
    // omitted name for parameter
    function func(uint k, uint) public pure returns(uint) {
        return k;
    }
}

The code above has two parameters: k and another unnamed parameter.

What is the point of having an unnamed parameter?

One use case I can think of is function overriding but what else can it be used for? Is it okay if we won't pass unnamed parameter?

Best Answer

I think you got it. Overriding, and then sometimes you'll see this kind of thing if you're trying to subscribe to a standard (e.g. ERC721) and you actually don't need that variable for how you're handling the implementation.

Related Solutions

Solidity – Handling Unimplemented Functions in Contracts

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

[Ethereum] Solidity assembly function call parameter alignment

Couldn't find an answer so ran following example in remix. while reusing code from here. And conclusion is, address should be padded to 32 bytes.

pragma solidity 0.4.18;


contract TestAddress {

    function isSameAddress(address a, address b) returns(bool){  //Simply add the two arguments and return
        if (a == b) return true;
        return false;
    }

    function() public {  //If the function signature doesn't check out, return -1
        revert();
    }
}

contract TestAllignment {
    TestAddress test;

    function TestAllignment(){  //Constructor function
        test = new TestAddress();
    }

    function testAsem() public view returns (bool same) {
        address contractAddr = address(test);  
        bytes4 sig = bytes4(keccak256("isSameAddress(address,address)")); //Function signature
        address a = msg.sender;

        assembly {
            let x := mload(0x40)   //Find empty storage location using "free memory pointer"
            mstore(x,sig) //Place signature at begining of empty storage 
            mstore(add(x,0x04),a) // first address parameter. just after signature
            mstore(add(x,0x24),a) // 2nd address parameter - first padded. add 32 bytes (not 20 bytes)
            mstore(0x40,add(x,0x64)) // this is missing in other examples. Set free pointer before function call. so it is used by called function.
             // new free pointer position after the output values of the called function.

            let success := call(      
                            5000, //5k gas
                            contractAddr, //To addr
                            0,    //No wei passed
                            x,    // Inputs are at location x
                            0x44, //Inputs size two padded, so 68 bytes
                            x,    //Store output over input
                            0x20) //Output is 32 bytes long

            same := mload(x)       //Assign output value
            mstore(0x40,add(x,0x20)) // Set storage pointer to empty space
        }

        return same;
    }

    function testSol() public view returns(bool same){ //Make sure the Test1 function works properly
        address add = msg.sender;

        same = test.isSameAddress(add,add); 
    }
}

Thanks to Tjaden for the code example.

Best Answer

Related Solutions

Solidity – Handling Unimplemented Functions in Contracts

[Ethereum] Solidity assembly function call parameter alignment

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