smart contract sample code

smart-contract.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.8.0;

contract SolidityTest {
//    constructor() public{
//    }
   function getResult() public view returns(uint){
      uint a = 6;
      uint b = 10;
      return a + b;
   }
}

// ===============================================

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.8.0;

contract DataStorge {
    uint storeData;

    function set(uint x) public {
        storeData = x;
        // storeData = block.difficulty; //encrypts the data of the variable
        // storeData = block.timestamp;
        // storeData = block.number;
    }

    function get() public view returns(uint result) {
        return storeData;
    }
}

// ===================================================

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.8.0;

contract donutMachine {
    address public owner;

    mapping (address => uint) public numberOfDonut;

    constructor() {
        owner = msg.sender;
        numberOfDonut[address(this)] = 200;
    }

    function getRemaingDonuts() public view returns(uint) {
        return numberOfDonut[address(this)];
    }

    function purchase(uint amount) public payable {
        require(msg.value >= amount * 2 ether, "You must pay 2 ETH per donut");
        require(numberOfDonut[address(this)] >= amount);
        numberOfDonut[address(this)] -= amount;
        numberOfDonut[msg.sender] += amount;
    }

    function restock(uint amount) public {
        require(msg.sender == owner, "Only the owner can restock");
        numberOfDonut[address(this)] += amount;
    }
}