Simple Ethereum smart contract for sending text messages.

MesChain.sol

pragma solidity ^0.4.0;

contract Messenger {
    struct MsgDB {
        uint totalMessages;
        mapping (uint => string) message;
    }
    struct Message {
            string text;
            string date;
        }
    mapping (address => mapping (address => MsgDB)) dialogues;
    
    function  IsBigger (address x, address y) private returns (bool) {
        return (x > y);
    }
    function Send(address addr, string text) {
        address x;
        address y;
        if (IsBigger(addr, msg.sender)) {
            x = addr;
            y = msg.sender;
        }
        else {
            x = msg.sender;
            y = addr;
        }
       // if (dialogues[x][y] == 0) {
         //   dialogues[x][y] =  MsgDB;
        //}
        var i = ++dialogues[x][y].totalMessages;
        dialogues[x][y].message[i] = text;
    }
    
    function Receive(address addr, uint i) returns (string) {
        address x;
        address y;
        if (IsBigger(addr, msg.sender)) {
            x = addr;
            y = msg.sender;
        }
        else {
            x = msg.sender;
            y = addr;
        }
        if (i > dialogues[x][y].totalMessages) {
            i = dialogues[x][y].totalMessages;
        }
        return dialogues[x][y].message[i];
    }
}