3

Please find the below ethereum token creation contract. It has two burn functions. It is having redendent params also.

Why it is placed, what is the importance of the functions.

pragma solidity ^0.4.8;
contract tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData); }

contract MyToken {
    /* Public variables of the token */
    string public standard = 'Token 0.1';
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;

/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
mapping (address => mapping (address => uint256)) public allowance;

/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);

/* This notifies clients about the amount burnt */
event Burn(address indexed from, uint256 value);

/* Initializes contract with initial supply tokens to the creator of the contract */
function MyToken(
    uint256 initialSupply,
    string tokenName,
    uint8 decimalUnits,
    string tokenSymbol
    ) {
    balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
    totalSupply = initialSupply;                        // Update total supply
    name = tokenName;                                   // Set the name for display purposes
    symbol = tokenSymbol;                               // Set the symbol for display purposes
    decimals = decimalUnits;                            // Amount of decimals for display purposes
}

/* Send coins */
function transfer(address _to, uint256 _value) {
    if (_to == 0x0) throw;                               // Prevent transfer to 0x0 address
    if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
    if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
    balanceOf[msg.sender] -= _value;                     // Subtract from the sender
    balanceOf[_to] += _value;                            // Add the same to the recipient
    Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
}

/* Allow another contract to spend some tokens in your behalf */
function approve(address _spender, uint256 _value)
    returns (bool success) {
    allowance[msg.sender][_spender] = _value;
    return true;
}

/* Approve and then comunicate the approved contract in a single tx */
function approveAndCall(address _spender, uint256 _value, bytes _extraData)
    returns (bool success) {
    tokenRecipient spender = tokenRecipient(_spender);
    if (approve(_spender, _value)) {
        spender.receiveApproval(msg.sender, _value, this, _extraData);
        return true;
    }
}        

/* A contract attempts to get the coins */
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
    if (_to == 0x0) throw;                                // Prevent transfer to 0x0 address
    if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
    if (balanceOf[_to] + _value < balanceOf[_to]) throw;  // Check for overflows
    if (_value > allowance[_from][msg.sender]) throw;     // Check allowance
    balanceOf[_from] -= _value;                           // Subtract from the sender
    balanceOf[_to] += _value;                             // Add the same to the recipient
    allowance[_from][msg.sender] -= _value;
    Transfer(_from, _to, _value);
    return true;
}

function burn() payable returns (bool success) {
    if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
    balanceOf[_from] -= _value;                          // Subtract from the sender
    Burn(_from, _value);
    return true;
}

function burnFrom(address _from) payable returns (bool success) {
    if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
    if (_value > allowance[_from][msg.sender]) throw;   // Check allowance
    balanceOf[_from] -= _value;                          // Subtract from the sender
    Burn(_from, _value);
    return true;
}

}

these functions are missing some params, could some one explain this?

-1

As is, this code does not compile. This is because, as you state, some of the params for the burn function and the burnFrom function are missing.

I got it to compile by changing burn() to burn(address _from, uint _value) and burnFrom(address _from) to burnFrom(address _from, uint _value). (By the way, you can test this using Browser Solidity.) Hope that helps :)

Where did you find this code?

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