Simple Namecoin contract

namecoin.sol

contract Namecoin {
  uint registrationCost;
  mapping (string => string) public domains;

  function Namecoin(uint _cost) {
    registrationCost = _cost;
  }
  
  function register(string _domainName, string _ip) {
    if (msg.value < registrationCost) throw;
    if (domains[_domainName]) throw;
    
    domains[_domainName] = _ip;
  }

}