AuctionHouse2 Docs
Fall 2024
API

# EnglishAuction

o1.auctionhouse.EnglishAuction
class EnglishAuction(`description`: String, val `startingPrice`: Int, `duration`: Int) extends ItemForSale

The class EnglishAuction represents “normal”, “English-style” auctions in an electronic auction house. Each auction object represents an auction for a single item that has been put up for sale.

Each English auction has a starting price for the item being sold. No bids lower than the starting price are accepted. The highest bidder wins the item at the end of the auction. If two bidders bid the same amount, the first bidder wins over the later one. Apart from this, the order in which bids are placed is not significant.

Upon creation, a duration (in days) is set for the auction. Every day, the method `advanceOneDay` must be called to update the auction status. Once the time limit is reached, the auction closes and the highest bid wins. If there were no bids made by this time, the auction closes anyway and is considered “expired”.

In a traditional non-electronic auction, all bidders are physically present, and it is very common for the same person to make multiple slightly increased bids during the course of the auction, which only lasts a relatively short time. The bidding system in an electronic “English auction” is different. When bidding, bidders indicate the maximum price that they are willing to pay for the item. Storing the maximum bid amount in the electronic auction house is convenient, as it allows bidders to indicate how far they are willing to go, without having to come back to the auction house service repeatedly to increase their bids.

Even if a bidder later wins the auction, they do not necessarily have to pay the full maximum price indicated when placing the bid. They only need to pay enough to beat the second highest bidder. Consider an example. Say bidder A has bid a maximum of 100 for an item and bidder B has bid 150, and the auction then closes. B wins the item and has to pay a price of 101 for it, just enough to beat A’s 100.

The maximum bid amount of the leading bidder is not publicly displayed. The program is intended to display only the current price of the auction and the minimum amount that new bidders must bid in order to stand any chance of winning. For instance, say bidder A has placed a bid with a limit of 200 for an item, and bidder B has placed a bid with a limit of 300. The current price of the auction is now 201. The minimum amount that new bidders must bid is 202 (good enough to beat 201). B’s limit of 300 will not become apparent to other bidders unless someone bids over 300, thereby becoming the leading bidder. (Not displaying the leading bidder’s limit is a sensible policy. Otherwise, bidders or sellers could raise the price without any intention of actually winning the item.)

See Huuto.Net or eBay for descriptions of similar real-world systems.

This simple class does not support bid cancellations, reserve prices, item buyouts, etc., and does not store any seller information.

## Parameters

description

  a short description of the item

duration

  the length of the auction, in days

startingPrice

  the initial price of the item, that is, the lowest possible price the seller is willing to accept

## Attributes

See also

  Bid

Graph
Supertypes
  trait ItemForSale
  class Object
  trait Matchable
  class Any

## Members list

### Value members

#### Concrete methods

def advanceOneDay(): Unit

Records one day as having passed. For an English auction, this simply means that if the auction is still open, its remaining duration is shortened by one day.

Records one day as having passed. For an English auction, this simply means that if the auction is still open, its remaining duration is shortened by one day.

## Attributes

def bid(`bidder`: String, `amount`: Int): Boolean

Places a bid on the item, assuming that the auction is open and the bid is sufficiently high. If those conditions are not met, this method has no effect.

Places a bid on the item, assuming that the auction is open and the bid is sufficiently high. If those conditions are not met, this method has no effect.

## Parameters

amount

  the maximum amount the bidder is willing to pay for the item

bidder

  the name of the bidder

## Attributes

Returns

  a Boolean value indicating whether the new bid is now the leading bid for the item

def buyer: Option[String]

Returns the winner of the auction, or the current highest bidder if the auction has not closed yet. The person’s name is wrapped in an `Option`; `None` is returned if no bids have been made.

Returns the winner of the auction, or the current highest bidder if the auction has not closed yet. The person’s name is wrapped in an `Option`; `None` is returned if no bids have been made.

## Attributes

def daysLeft: Int

Returns the number of days left before the auction closes. A return value of zero indicates that time has run out and the auction has closed.

Returns the number of days left before the auction closes. A return value of zero indicates that time has run out and the auction has closed.

## Attributes

def hasNoBids: Boolean

Determines whether not a single bid has been placed yet.

Determines whether not a single bid has been placed yet.

## Attributes

def isExpired: Boolean

Determines if the auction has expired, that is, if it has ended without the item being sold. An English auction expires if the allocated duration has passed and no bids have been made.

Determines if the auction has expired, that is, if it has ended without the item being sold. An English auction expires if the allocated duration has passed and no bids have been made.

## Attributes

def isOpen: Boolean

Determines if the auction is open, that is, if the item can still be bought. An English auction is always open if its allocated duration has not been reached yet.

Determines if the auction is open, that is, if the item can still be bought. An English auction is always open if its allocated duration has not been reached yet.

## Attributes

def price: Int

Returns the price the item is currently selling for, that is, the money that the currently winning bidder would have to pay if the auction were to close now (or must pay if the auction is already closed).

Returns the price the item is currently selling for, that is, the money that the currently winning bidder would have to pay if the auction were to close now (or must pay if the auction is already closed).

If there are no bids or there is just a single bid on the item, the current price equals the starting price of the item. If there is more than one bid, then the current price is the price that is just enough for the highest bidder to beat the second highest bidder (as described in the introduction to this class).

Note that if the two highest bids are equal, the first bidder always wins over the second. The first bidder does not have to pay over their bid limit simply because someone else also bid the same amount.

## Attributes

def requiredBid: Int

Returns the lowest amount that a would-be bidder will have to bid for this item so as to stand a chance of winning the auction. If there are no bids on the item yet, the minimum bid amount equals the starting price of the auction. Otherwise, the bid amount must be higher than the current price of the auction. (See the introduction to this class for an example.)

Returns the lowest amount that a would-be bidder will have to bid for this item so as to stand a chance of winning the auction. If there are no bids on the item yet, the minimum bid amount equals the starting price of the auction. Otherwise, the bid amount must be higher than the current price of the auction. (See the introduction to this class for an example.)

## Attributes

See also

  price

#### Inherited methods

override def toString: String

Returns a textual description of the item. This text is the same as that returned by `description`.

Returns a textual description of the item. This text is the same as that returned by `description`.

## Attributes

Definition Classes
  ItemForSale -> Any
Inherited from:
  ItemForSale

#### Concrete fields

val startingPrice: Int