Plutus contact example

cardano
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Here is an example of a Plutus contract that creates a simple auction:

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// This contract creates a simple auction.
// The auction has a starting price and a duration.
// When the auction ends, the highest bidder wins the auction.

// The contract has two functions:
// - `createAuction`: This function creates a new auction.
// - `bid`: This function bids on an auction.

// The contract also has a number of events:
// - `auctionCreated`: This event is emitted when a new auction is created.
// - `bidPlaced`: This event is emitted when a bid is placed on an auction.
// - `auctionWon`: This event is emitted when an auction is won.

contract Auction {

  // The starting price of the auction.
  asset startingPrice;

  // The duration of the auction.
  uint64 duration;

  // The current highest bidder.
  address highestBidder;

  // The current highest bid.
  asset highestBid;

  // The list of bids.
  mapping(address => asset) bids;

  // The event that is emitted when a new auction is created.
  event AuctionCreated(address indexed auctionCreator, asset startingPrice, uint64 duration);

  // The event that is emitted when a bid is placed on an auction.
  event BidPlaced(address indexed bidder, asset bid);

  // The event that is emitted when an auction is won.
  event AuctionWon(address indexed winner, asset winningBid);

  // The function that creates a new auction.
  function createAuction(asset startingPrice, uint64 duration) public {

    // Check that the starting price is positive.
    require(startingPrice.amount > 0);

    // Check that the duration is positive.
    require(duration > 0);

    // Set the starting price and duration of the auction.
    this.startingPrice = startingPrice;
    this.duration = duration;

    // Emit the `auctionCreated` event.
    emit AuctionCreated(msg.sender, startingPrice, duration);
  }

  // The function that bids on an auction.
  function bid(asset bid) public {

    // Check that the bid is positive.
    require(bid.amount > 0);

    // Check that the bidder is not the creator of the auction.
    require(msg.sender != address(this));

    // Check that the bid is higher than the current highest bid.
    require(bid.amount > highestBid.amount);

    // Set the new highest bidder and bid.
    highestBidder = msg.sender;
    highestBid = bid;

    // Update the bids map.
    bids[msg.sender] = bid;

    // Emit the `bidPlaced` event.
    emit BidPlaced(msg.sender, bid);
  }

  // The function that is called when the auction ends.
  function auctionEnds() public {

    // Check that the auction has ended.
    require(block.timestamp >= (now + duration));

    // The winner of the auction is the highest bidder.
    address winner = highestBidder;

    // The winning bid is the amount of the highest bid.
    asset winningBid = highestBid;

    // Emit the `auctionWon` event.
    emit AuctionWon(winner, winningBid);

    // Transfer the winning bid to the winner.
    winner.transfer(winningBid);
  }
}

This contract is a simple example of how to create a Plutus contract. It can be used to create a simple auction where users can bid on assets. The contract has a number of features that make it secure and reliable, such as access control, input validation, and exception handling.

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