pragma solidity ^0.4.16;

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract RollToken {

        string public name;  
        string public symbol;  
        uint8 public decimals = 18; 
        uint256 public total = 1000000000;
        uint256 public totalSupply; 

        mapping (address => uint256) public balanceOf;
        mapping (address => mapping (address => uint256)) public allowance;
        event Transfer(address indexed from, address indexed to, uint256 value);

        event Burn(address indexed from, uint256 value);


        function RollToken( ) public {

                totalSupply = total * 10 ** uint256(decimals);

                balanceOf[msg.sender] = totalSupply;

                name = "Roll"; 

                symbol = "Roll";

        }

     function _transfer(address _from, address _to, uint _value) internal {
    
        require(_to != 0x0);
     
        require(balanceOf[_from] >= _value);
     
        require(balanceOf[_to] + _value >= balanceOf[_to]);
  
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
   
        balanceOf[_from] -= _value;
    
        balanceOf[_to] += _value;
        Transfer(_from, _to, _value);
  
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }


    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }


    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

 
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }


    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }


    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   
        balanceOf[msg.sender] -= _value;            
        totalSupply -= _value;                     
        Burn(msg.sender, _value);
        return true;
    }


    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                
        require(_value <= allowance[_from][msg.sender]);    
        balanceOf[_from] -= _value;                       
        allowance[_from][msg.sender] -= _value;            
        totalSupply -= _value;                            
        Burn(_from, _value);
        return true;
    }   

}