atisheksingh

//SPDX-License-Identifier: MIT
// https://community.optimism.io/docs/developers/bedrock/differences/#l1-contracts
pragma solidity 0.8.10;

import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";

/**
 * @title L2OutputOracle
 * @notice The L2 state is committed to in this contract
 * The payable keyword is used on appendL2Output to save gas on the msg.value check.

atisheksingh

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.11;

import "@chainlink/contracts/src/v0.8/VRFConsumerBase.sol";

contract Ownable_Page_Lottery is VRFConsumerBase {
    address public owner;
    address payable[] public players;
    uint public lotteryId;

atisheksingh

// To enable meta transaction, let create a generic method that calls executeMetaTransaction by taking the user signature
// and then execute transaction via Biconomy

// Dependencies
import {toBuffer} from "ethereumjs-util";
import abi from "ethereumjs-abi";
import events from "events";

// Initialization of web3
let web3 = new Web3(window.ethereum);

atisheksingh

Use cases

• Optional/nullable data types.
• Variant data types.
• Flag with extra information needed only in some cases (or different in different cases).
• Modeling states in a state machine where each state can have some data associated with it.
• List of operations for batch processing, where each operation can have its own arguments.
• Alternative to function overloading that allows avoiding combinatorial explosion when there are multiple parameters that need variants.
• Nested data structures with heterogenous nodes.

Syntax and semantics

atisheksingh

Compile

npx hardhat compile

Run unit tests

npx hardhat test

Start local node

npx hardhat node

Deploy to Rinkeby

atisheksingh

pragma solidity 0.6.12;

import '@pancakeswap/pancake-swap-lib/contracts/math/SafeMath.sol';
import '@pancakeswap/pancake-swap-lib/contracts/token/BEP20/IBEP20.sol';
import '@pancakeswap/pancake-swap-lib/contracts/token/BEP20/SafeBEP20.sol';
import '@pancakeswap/pancake-swap-lib/contracts/access/Ownable.sol';

// import "@nomiclabs/buidler/console.sol";

interface IWBNB {