Blackjack 1
1

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This worksheet is copyright © Richard Pawson 2025, and protected by the Creative Commons license: Attribution-NonCommercial-NoDerivatives 4.0 International. You may freely make and distribute copies of this worksheet as is, but if you modify this worksheet you may not distribute your modified version (outside your own teaching institution) without the author's permission. Please email the author to report errors or suggest improvements.

# Step 1: learning the rules of Blackjack

Watch the first video:

Now
# f9dcff83372dc8408276b3d13e4d94c152045baea4e93c37ee2cdafa18102b34 Elan 2.0.0-alpha valid main variable game set to new Game(1000) call game.addPlayer(new HumanPlayer("Player A", 1000)) variable anotherRound set to true while anotherRound call playOneRound(game) call game.setMessage("Points updated. Do you want to play another round? (press y or n)") call clearKeyBuffer() call display(game) variable k set to waitForKey().lowerCase() if k.equals("y") then call game.setMessage("") else set anotherRound to false end if end while end main procedure playOneRound(game as Game) call game.newRound() call display(game) variable dealer set to game.dealer variable faceCard set to dealer.faceCard.getValue() for player in game.players call player.startTurn() call display(game) while player.status is Status.active call player.nextAction(faceCard) call display(game) end while end for call dealer.play() call display(game) while dealer.status is Status.active call dealer.nextAction(faceCard) call display(game) end while call game.updatePoints() end procedure procedure display(game as Game) variable html set to $"<style>{styleSheet}</style>{htmlForGame(game)}" call displayHtml(html) call sleep(1.5) end procedure procedure updatePoints(dealer as Dealer, player as Player, playerOutcome as Outcome) if playerOutcome is Outcome.winDouble then call player.changePointsBy(2) call dealer.changePointsBy(-2) elif playerOutcome is Outcome.win then call player.changePointsBy(1) call dealer.changePointsBy(-1) elif playerOutcome is Outcome.lose then call player.changePointsBy(-1) call dealer.changePointsBy(1) end if end procedure function determinePlayerOutcome(dealer as Dealer, player as Player) returns Outcome # These 'let' definitions are just to make the logic that follows them simpler to read variable d set to dealer.status variable dTotal set to dealer.handTotal variable p set to player.status variable pTotal set to player.handTotal variable bust set to Status.bust variable bj set to Status.blackjack variable win set to Outcome.win variable winDouble set to Outcome.winDouble variable lose set to Outcome.lose variable draw set to Outcome.draw variable playerOutcome set to draw if p is bust then set playerOutcome to lose elif (p is bj) and (d isnt bj) then set playerOutcome to winDouble elif d is bust then set playerOutcome to win elif (d is bj) and (p is bj) then set playerOutcome to draw elif p is bj then set playerOutcome to winDouble elif d is bj then set playerOutcome to lose elif pTotal > dTotal then set playerOutcome to win elif pTotal < dTotal then set playerOutcome to lose else # strictly, this 'else' clause is redundant - as the variable was initialised to 'draw' - but added for clarity set playerOutcome to draw end if return playerOutcome end function test test_determinePlayerOutcome variable dbj set to new Dealer(0) with status set to Status.blackjack variable d21 set to new Dealer(0) with status set to Status.standing, handTotal set to 21 variable d17 set to new Dealer(0) with status set to Status.standing, handTotal set to 17 variable dbu set to new Dealer(0) with status set to Status.bust variable pbj set to new HumanPlayer("", 0) with status set to Status.blackjack variable p21 set to new HumanPlayer("", 0) with status set to Status.standing, handTotal set to 21 variable p17 set to new HumanPlayer("", 0) with status set to Status.standing, handTotal set to 17 variable pbu set to new HumanPlayer("", 0) with status set to Status.bust assert determinePlayerOutcome(dbj, pbj) is Outcome.draw assert determinePlayerOutcome(dbj, p21) is Outcome.lose assert determinePlayerOutcome(dbj, pbu) is Outcome.lose assert determinePlayerOutcome(d21, pbj) is Outcome.winDouble assert determinePlayerOutcome(d21, p21) is Outcome.draw assert determinePlayerOutcome(d21, p17) is Outcome.lose assert determinePlayerOutcome(d21, pbu) is Outcome.lose assert determinePlayerOutcome(dbu, pbj) is Outcome.winDouble assert determinePlayerOutcome(dbu, p17) is Outcome.win assert determinePlayerOutcome(dbu, pbu) is Outcome.lose end test function dealCard(random as Float) returns Card variable number set to (random*52).floor() variable rank set to rankValue().keys()[divAsInt(number, 4)] variable suit set to number mod 4 return new Card(rank, intAsSuit(suit), false) end function test test_dealCard variable c1 set to dealCard(0) assert c1.rank is "2" assert c1.suit is Suit.clubs variable c2 set to dealCard(0.9999999) assert c2.rank is "A" assert c2.suit is Suit.spades variable c3 set to dealCard(0.5) assert c3.rank is "8" assert c3.suit is Suit.hearts variable c4 set to dealCard(0.24) assert c4.rank is "5" assert c4.suit is Suit.clubs end test function intAsSuit(n as Int) returns Suit variable suit set to Suit.clubs if n is 1 then set suit to Suit.diamonds elif n is 2 then set suit to Suit.hearts elif n is 3 then set suit to Suit.spades end if return suit end function test test_intAsSuit assert intAsSuit(0) is Suit.clubs assert intAsSuit(1) is Suit.diamonds assert intAsSuit(2) is Suit.hearts assert intAsSuit(3) is Suit.spades end test function htmlForGame(game as Game) returns String variable html set to "<div class='game'>" set html to html + htmlForPlayer(game.dealer) for player in game.players set html to html + htmlForPlayer(player) end for set html to html + $"<div class='message'>{game.message}</div>" return html + "</div>" end function test test_htmlForGame variable c1 set to new Card("3", Suit.clubs, false) variable c2 set to new Card("K", Suit.spades, true) variable p set to new HumanPlayer("fred", 10) with cards set to [c1, c2] variable players set to (new List<of Player>()).withAppend(p) variable g2 set to new Game(1) with players set to players assert htmlForGame(g2) is "<div class='game'><div class='player'><div class='details'>Dealer - 1 points </div><div class='hand'></div></div><div class='player'><div class='details'>fred - 10 points - hand total: 0</div><div class='hand'><div class='card black'><div class='u'>3</div><div class='v'>&amp;clubs;</div><div class='a'>&amp;clubs;</div><div class='b'>&amp;clubs;</div><div class='c'>&amp;clubs;</div></div><div class='card reversed'></div></div></div><div class='message'></div></div>" end test function htmlForPlayer(player as Player) returns String variable html set to "<div class='player'>" set html to html + $"<div class='details'>{player.name} - {player.points} points {player.getMessage()}</div>" set html to html + "<div class='hand'>" for card in player.cards variable suit set to card.suit variable rank set to card.rank set html to html + htmlForCard(card) end for return html + "</div></div>" end function test test_htmlForPlayer variable c1 set to new Card("3", Suit.clubs, false) variable c2 set to new Card("K", Suit.spades, true) variable p set to new HumanPlayer("charlie", 10) with cards set to [c1, c2] assert htmlForPlayer(p) is "<div class='player'><div class='details'>charlie - 10 points - hand total: 0</div><div class='hand'><div class='card black'><div class='u'>3</div><div class='v'>&amp;clubs;</div><div class='a'>&amp;clubs;</div><div class='b'>&amp;clubs;</div><div class='c'>&amp;clubs;</div></div><div class='card reversed'></div></div></div>" end test function htmlForCard(card as Card) returns String variable html set to "" if card.faceDown then set html to "<div class='card reversed'>" else variable rank set to card.rank variable suit set to card.suit variable colour set to colourForSuit(suit) variable symbol set to symbolForSuit(suit) set html to $"<div class='card {colour}'>" variable u set to htmlForSpot("u", rank) variable v set to htmlForSpot("v", symbol) variable grid set to "" for location in gridForRank(rank) if location.equals("royal") then set grid to grid + htmlForSpot(location, rank) else set grid to grid + htmlForSpot(location, symbol) end if end for set html to html + $"{u}{v}{grid}" end if return html + "</div>" end function test test_htmlForCard variable c1 set to new Card("3", Suit.clubs, false) assert htmlForCard(c1) is "<div class='card black'><div class='u'>3</div><div class='v'>&amp;clubs;</div><div class='a'>&amp;clubs;</div><div class='b'>&amp;clubs;</div><div class='c'>&amp;clubs;</div></div>" variable c2 set to new Card("K", Suit.spades, true) assert htmlForCard(c2) is "<div class='card reversed'></div>" end test function htmlForSpot(id as String, content as String) returns String return $"<div class='{id}'>{content}</div>" end function test test_htmlForSpot assert htmlForSpot("c", "&amp;hearts;") is "<div class='c'>&amp;hearts;</div>" assert htmlForSpot("u", "10") is "<div class='u'>10</div>" end test class Game constructor(dealerStartPoints as Int) set this.dealer to new Dealer(dealerStartPoints) set this.players to new List<of Player>() set this.message to "" end constructor property dealer as Dealer property players as List<of Player> property message as String procedure newRound() variable dealer set to this.dealer call dealer.newHand() for player in this.players call player.newHand() end for end procedure procedure updatePoints() for player in this.players variable playerOutcome set to determinePlayerOutcome(this.dealer, player) call global.updatePoints(this.dealer, player, playerOutcome) end for end procedure procedure addPlayer(player as Player) variable players set to this.players call players.append(player) end procedure procedure setMessage(message as String) set this.message to message end procedure end class class Card property suit as Suit property rank as String property faceDown as Boolean constructor(rank as String, suit as Suit, facedown as Boolean) set this.rank to rank set this.suit to suit set this.faceDown to facedown end constructor procedure turnFaceUp() set this.faceDown to false end procedure procedure turnFaceDown() set this.faceDown to true end procedure end class abstract class Player property name as String property points as Int property cards as List<of Card> property handTotal as Int property softAce as Boolean property status as Status property hasTurn as Boolean procedure startTurn() if this.status is Status.active then set this.hasTurn to true end if end procedure procedure evaluateStatus(newCard as Card) if (cardCount() is 2) and (this.handTotal is 21) then set this.status to Status.blackjack elif (this.handTotal > 21) and (this.softAce) then set this.handTotal to this.handTotal - 10 set this.softAce to false elif this.handTotal > 21 then set this.status to Status.bust elif this.handTotal is 21 then set this.status to Status.standing end if if this.status isnt Status.active then set this.hasTurn to false end if end procedure procedure stand() set this.status to Status.standing set this.hasTurn to false end procedure procedure draw() variable newCard set to dealCard(random()) variable cards set to this.cards call cards.append(newCard) if newCard.rank.equals("A") then call addAce() else set this.handTotal to this.handTotal + rankValue()[newCard.rank] end if call evaluateStatus(newCard) end procedure procedure addAce() if this.softAce then set this.handTotal to this.handTotal + 1 else set this.handTotal to this.handTotal + 11 set this.softAce to true end if end procedure function cardCount() returns Int return this.cards.length() end function procedure changePointsBy(amount as Int) set this.points to this.points + amount end procedure abstract procedure newHand() procedure newHandHelper() set this.hasTurn to false set this.softAce to false set this.cards to new List<of Card>() set this.handTotal to 0 set this.status to Status.active call draw() call draw() end procedure abstract function getMessage() returns String function statusAsString() returns String variable msg set to "" variable status set to this.status if this.hasTurn then set msg to msg + " - PLAYING" elif status is Status.standing then set msg to msg + " - STANDING" elif status is Status.blackjack then set msg to msg + " - BLACKJACK" elif status is Status.bust then set msg to msg + " - BUST" end if return msg end function abstract procedure nextAction(dealerFaceCard as Card) end class class Dealer inherits Player constructor(startingPoints as Int) set this.name to "Dealer" set this.points to startingPoints set this.faceCard to new Maybe<of Card>() end constructor property faceCard as Maybe<of Card> property hasPlayed as Boolean procedure play() call startTurn() variable hiddenCard set to this.cards[1] call hiddenCard.turnFaceUp() set this.hasPlayed to true end procedure procedure newHand() set this.hasPlayed to false call newHandHelper() variable faceCard set to this.faceCard call faceCard.set(this.cards[0]) variable hiddenCard set to this.cards[1] call hiddenCard.turnFaceDown() end procedure procedure nextAction(faceCard as Card) if this.handTotal < 17 then call draw() else call stand() end if end procedure function getMessage() returns String variable msg set to "" if this.hasPlayed then set msg to statusAsString() + $" - hand total: {this.handTotal}" end if return msg end function end class class HumanPlayer inherits Player constructor(name as String, startingPoints as Int) set this.name to name set this.points to startingPoints end constructor procedure newHand() call newHandHelper() end procedure procedure nextAction(dealerFaceCard as Card) variable key set to "" call clearKeyBuffer() while key.equals("") set key to waitForKey() if key.equals("d") then call draw() elif key.equals("s") then call stand() else set key to "" end if end while end procedure function getMessage() returns String variable msg set to statusAsString() + $"- hand total: {this.handTotal}" if this.hasTurn then set msg to msg + " - press 'd' to draw, 's' to stand" end if return msg end function end class enum Action stand, draw enum Outcome undecided, lose, draw, win, winDouble enum Status active, standing, blackjack, bust enum Suit clubs, diamonds, hearts, spades function symbolForSuit(suit as Suit) returns String variable dict set to [Suit.clubs:"&amp;clubs;", Suit.diamonds:"&amp;diams;", Suit.hearts:"&amp;hearts;", Suit.spades:"&amp;spades;"] return dict[suit] end function function rankValue() returns Dictionary<of String, Int> return ["2":2, "3":3, "4":4, "5":5, "6":6, "7":7, "8":8, "9":9, "10":10, "J":10, "Q":10, "K":10, "A":11] end function function gridForRank(rank as String) returns List<of String> variable dict set to ["A":["royal"], "2":["b", "c"], "3":["a", "b", "c"], "4":["d", "e", "f", "g"], "5":["a", "d", "e", "f", "g"], "6":["d", "e", "f", "g", "h", "i"], "7":["d", "e", "f", "g", "h", "i", "l"], "8":["d", "e", "f", "g", "h", "i", "l", "m"], "9":["a", "d", "e", "f", "g", "n", "o", "p", "r"], "10":["d", "e", "f", "g", "n", "o", "p", "r", "s", "t"], "J":["royal"], "Q":["royal"], "K":["royal"]] return dict[rank] end function function colourForSuit(suit as Suit) returns String variable dict set to [Suit.clubs:"black", Suit.diamonds:"red", Suit.hearts:"red", Suit.spades:"black"] return dict[suit] end function constant styleSheet set to ':root { background-color: darkgreen; padding-left: 5px;}.game { padding: 5px;}.message, .details { color: white; font-family: Arial, Helvetica, sans-serif;}.hand { margin-top: 5px; height: 150px; padding-bottom: 10px; } .card { position: relative; float: left; background-color: white; width: 95px; height:140px; margin-right:10px; padding: 5px; border-radius: 5px; font-family: Helvetica, sans-serif; }.royal,.a,.b,.c,.d,.e,.f,.g,.h,.i,.j,.k,.l,.m,.n,.o,.p,.q,.r,.s,.t,.u,.v,.w,.x,.y,.z {position: absolute; text-align:center;}/* Standard spots */ .a,.b,.c,.d,.e,.f,.g,.h,.i,.l,.m,.n,.o,.p,.r,.s,.t {font-size: 30px;} /* columns */ .d,.n,.h,.p,.f {left: 18px } .a,.b,.c,.l,.m,.s,.t {left: 43px;} .e,.o,.i,.r,.g {left: 68px} /* rows */ .d,.b,.e {top: 0px} .s {top: 20px;} .l {top: 28px;} .n,.o {top: 37px;} .h,.a,.i {top: 57px} .p,.r {top: 75px;} .m {top: 86px;} .t {top: 93px;} .f,.c,.g {top: 114px;}/* royals */ .royal { position: absolute; z-index: 1; width: 95px; height: 140px; line-height: 140px; font-size: 100px; }/* corner summary */ .u {font-size: 15px; width: 15px; text-align: center; left: 0px; top: 2px;} .v {font-size: 20px; width: 15px; text-align: center; left: 0px; top: 12px;}/* suit colors */ .red {color: red} .black {color: black}/* back */ .card.reversed { background-color: rgba(0, 0, 255, 0.607);}'
and immediately use file > auto save the code to your local file storage: because you will be making changes and want to ensure that your changes are saved.

When you run the program, the display tab will be shown in place of this worksheet, you can flip between them by clicking on the tab headings.

So, run the program now, either:

- using the mouse, by clicking on the run button at the top of the screen, or
- using the keyboard, by pressing Ctrl+r

and play exactly 10 rounds of Blackjack.

Make sure that you have grasped the following points:

- Most cards have a obvious numeric value. The Royal cards - Jack, Queen, King - each have the value 10. An Ace is special: it can be valued at 11, or at 1. An Ace valued at 11 is known as a 'soft Ace'. If a dealt card takes the hand total over 21 then a soft Ace is automatically devalued to 1.
- The aim is to get the value of your hand as close to 21 as you can - but if drawing a card causes the total to go over 21 then (unless you have a 'soft Ace') you will be 'BUST' and your turn is over.
- If the first two cards of any player total exactly 21 - which would require one Ace, and one Royal or 10 card - then you have 'BLACKJACK' - the best hand possible - so no further action is needed from you.
- When all hands have finished playing, the outcome is determined, points swapped as follows:
  - If a player is BUST then 1 point is passed from them to the dealer even the dealer is also BUST.
  - If a player has BLACKJACK then they gain 2 points from the dealer unless the dealer also has BLACKJACK, in which case it is a draw.
  - else, if the player is STANDING and the dealer has BLACKJACK the dealer gains one point from the player.
  - else, if the player is STANDING and their hand total is greater than the dealer's, the player gains one point from the dealer.
  - else, if the player is STANDING and their hand total is the same as the dealer's, it is a draw.
  - else, if the player's total is less than the dealer's, the dealer gains one point from the player.
- This program uses deck of multiple packs of cards: so there is a small chance that the same card may appear on screen more than once.

After playing 10 rounds, how many points did you, and the dealer, end up with?

If you have not already exited the program, click stop.

#### Notes

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# Step 2: start to explore the code

Watch the next video:

How many instructions are there in total within the Blackjack program (just find the largest instruction number)?

The initial keyword in an instruction defines the type of instruction. Find and list here at least five initial keywords not mentioned explicitly in the video:

#### Notes

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# Step 3: the different elements within instructions

Watch the next video:

List below the different colours that you can see being used within the code (they are all shown within the first 15 instructions):

What is the significance of the colour dark-blue, and black?

#### Notes

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# Step 4: comments

Watch the next video:

Scrolling through the code, find two comments, not including the one at the top showing the Elan version, and write down the instruction number immediately below each comment:

#### Notes

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# Step 5: identifiers

Watch the next video:

Find five identifiers used in the program - not including any that were mentioned in the video - and list them here:

#### Notes

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# Step 6: literals

Watch the next video:

Find an example of a literal number, and a literal string - not including any specifically mentioned in the video - and note their instruction numbers below:

#### Notes

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# Step 7: methods

Watch the next video:

Find five method names - not including any specifically mentioned in the video - and write them here:

#### Notes

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# Step 8: types

Which of the types mentioned in the video are defined within the standard Elan language (if necessary, watch the video again)?

#### Notes

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# Step 9: adding a new instruction

Watch the next video:

Your first task is to turn the program into a two-player game (not counting the dealer, played by the computer):

- Near the top of `main`, find this instruction:
  call game.addPlayerprocedureName?(new HumanPlayer("Player A", 1000)arguments?)0
  game.addPlayerprocedureName?(HumanPlayer("Player A", 1000)arguments?) # call procedure0
  game.addPlayerprocedureName?(new HumanPlayer("Player A", 1000)arguments?); // call procedure0
  game.addPlayerprocedureName?(New HumanPlayer("Player A", 1000)arguments?) ' call procedure0
  game.addPlayerprocedureName?(new HumanPlayer("Player A", 1000)arguments?); // call procedure0
  and immediately below it insert a new `call` instruction.
- Into the two editable fields type in the same code that you see in the instruction immediately above it, except that instead of `"Player A"`, write `"Player B"`. Note that:
  - your text will initially be black, but it will be coloured once you leave the field
  - a drop-down list will offer you some 'auto-completion' options, which can save typing and errors. You can select an option with the mouse or with the cursor ↑↓ keys and Enter.
  - You might see a message appear on the right, but you can ignore it for now, unless it is coloured red (you will also then see the word invalid or error appear) in which case you should Backspace to correct the mistake.
- When you have completed the new instruction, run the program, and take responsibility for both Player A and Player B (or, if you are pairing with another person, control one each).

When does the dealer play, now ?

#### Notes

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# Step 10: modifying an existing instruction

- Go back to the instruction that creates Player A and above itinsert a `let` instruction and note that this features two editable fields.
- In the first field enter `name1` and in the second field type in the following code using the auto-completions to help `input("Enter name for first player") Going back to the first field, try deleting the contents and typing `Name1`

  What message do you see within the code editor?

  And what do you observe in the 'status panel' - at the top of the screen, just to the right of the code editor?

  Then revert the field back to `name2`.`
`
- Select the instruction below this - in other words the one that you added previously - and Tab to the second field. Edit the contents, replacing the literal string `"Player A"` with `name2` (no quotation marks because this is an identifier that holds a string, not a literal string).
- Run the program. When asked, type in your own first name, finishing with the Enter key.

  Has the name you entered made a difference?

  There is an unwanted 'side effect' on the screen - what is it?

- To fix the unwanted side effect, insert the following new instruction immediatelyafter the second player is created and added to the game: `call clearPrintedText()`
- Now change the program so that it asks the user to enter a name for the second player, this time using the identifier `name2`.
- Run the program again, and confirm that you can now name both players.
`

`

What would happen if you define the second identifier as name2, but in the next line you were to write name1? (If you need to check, run the program)

And what if the the second identifier was still name2 but you used name3 in the following instruction? This time, can you even run the program to try it?

`

#### Notes

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# Congratulations! You have completed this worksheet

You have learned:

- How to load, run, and stop a program
- How to recognise the different kinds of instructions that make up a program, including compound instructions, which contain other instructions.
- How to navigate around the program, selecting different instructions in order to draw attention to them and as a prelude to modifying them.
- How to insert new instructions, delete instructions, and to undo changes when they didn't do what you wanted.

In the next worksheet - Blackjack 2 - you'll start to do some real programming, by defining and implementing the logic for a fully-automated Blackjack player - and then in the Blackjack 3 worksheet, pitting different automated players against each other for thousands of games, and using the outcome to refine the strategies.

In the meantime, if you have time, we recommend that you watch the following additional videos - that offer further techniques for navigating and editing instructions. Practice the techniques shown in each video, either while it is running, or immediately afterwards.

All the techniques for navigating and modifying instructions may be looked up in the Help tab. For example: show in Help