PreVNK(V)

contract Token {

    /// @return total amount of tokens
    function totalSupply() constant returns (uint256 supply) {}

    /// @param _owner The address from which the balance will be retrieved
    /// @return The balance
    function balanceOf(address _owner) constant returns (uint256 balance) {}

    /// @notice send `_value` token to `_to` from `msg.sender`
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transfer(address _to, uint256 _value) returns (bool success) {}

    /// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
    /// @param _from The address of the sender
    /// @param _to The address of the recipient
    /// @param _value The amount of token to be transferred
    /// @return Whether the transfer was successful or not
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {}

    /// @notice `msg.sender` approves `_addr` to spend `_value` tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _value The amount of wei to be approved for transfer
    /// @return Whether the approval was successful or not
    function approve(address _spender, uint256 _value) returns (bool success) {}

    /// @param _owner The address of the account owning tokens
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens allowed to spent
    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {}

    /// @param _new_amount The amount of new tokens to issue
    /// @return Whether the issuance is successful
    function issue(uint256 _new_amount) returns (bool success) {}
    

    /// @param _new_issuer The address that can issue new tokens
    /// @return Whether the issuance was successful
    function setIssuer(address _new_issuer) returns (bool success) {}    

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    //TransferFrom event is not standard yet (wrt ERC20), but is required to recreate state when only using events.
    event TransferFrom(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

contract PreVNK is Token {

    address issuer;
    string public name;
    string public symbol;
    uint8 public decimals;

    modifier ifissuer { if(issuer == tx.origin) _ }

    function PreVNK(uint256 _initial_amount, string _name, string _symbol, uint8 _decimals) {
        balances[msg.sender] = _initial_amount;
        total_supply = _initial_amount;
        issuer = tx.origin;
        name = _name;     
        symbol = _symbol;
        decimals = _decimals;
    }

    function issue(uint256 _new_amount) ifissuer returns (bool success) {
      balances[issuer] += _new_amount;
      total_supply += _new_amount;
      return true;
    }

    function setIssuer(address _new_issuer) ifissuer returns (bool success) {
      issuer = _new_issuer;
      return true;
    }

    function transfer(address _to, uint256 _value) returns (bool success) {
        //Default assumes totalSupply can't be over max (2^256 - 1).
        //If your token leaves out totalSupply and can issue more tokens as time goes on, you need to check if it doesn't wrap.
        //Replace the if with this one instead.
        //if (balances[msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
        if (balances[msg.sender] >= _value && _value > 0) {
            balances[msg.sender] -= _value;
            balances[_to] += _value;
            Transfer(msg.sender, _to, _value);
            return true;
        } else { return false; }
    }

    //NOTE: This function will throw errors wrt changing storage where it should not, due to the optimizer errors, IF not careful.
    //As it is now, it works for both earlier and newer solc versions. (NO need to change anything)
    //In the future, the TransferFrom event will be moved to just before "return true;" in order to make it more elegant (once the new solc version is out of develop).
    //If you want to move parts of this function around and it breaks, you'll need at least:
    //Over commit: https://github.com/ethereum/solidity/commit/67c855c583042ddee6261a9921239a3afd086c14 (last successfully working commit)
    //See issue for details: https://github.com/ethereum/solidity/issues/333 & issue: https://github.com/ethereum/solidity/issues/281
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        //same as above. Replace this line with the following if you want to protect against wrapping uints.
        //if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value > balances[_to]) {
        if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0) {
            balances[_to] += _value;
            TransferFrom(_from, _to, _value);
            balances[_from] -= _value;
            allowed[_from][msg.sender] -= _value;
            return true;
        } else { return false; }
    }

    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }

    function approve(address _spender, uint256 _value) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
      return allowed[_owner][_spender];
    }

    function totalSupply() constant returns (uint256 _total) {
        return total_supply;
    }

    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
    uint256 total_supply;
}