# simple subtraction dot dot dot and gambling

Jan 11, 2015

Continuing on the theme of the last two posts, here are two more examples, here are two more. The first is a simple change-counting program, which might fit the bill for a “first program”, and the second is a game of craps (not too interactive, unfortunately; all you do is place a bet – I did at least add a delay for the dice throw to make it seem less … er … automated).

### Change: Go Source

``````package main

import (
"fmt"
"math"
"strings"
)

type moneyUnit struct {
name  string
value int
}

var moneyUnits = []moneyUnit{
{"Hundred Dollar Bill", 100 * 100},
{"Fifty Dollar Bill", 50 * 100},
{"Twenty Dollar Bill", 20 * 100},
{"Ten Dollar Bill", 10 * 100},
{"Five Dollar Bill", 5 * 100},
{"One Dollar Bill", 100},
{"One-Half Dollar", 50},
{"Quarter", 25},
{"Dime", 10},
{"Nickel", 5},
{"Penny", 1},
}

func showUsage() {
fmt.Println("\n         The Change-Maker   ")
fmt.Println("----------------------------------\n")
}

func getMoney(prompt string) float64 {
for {
fmt.Printf("%s : \$", prompt)
roundPennies := math.Ceil(pennies)
if roundPennies-pennies > 1e-4 {
fmt.Println("Error: please enter \$XXXX.XX (i.e. up to two decimal places!)")
} else {
}
}
}

func deductChange(pennies, unit int) (numUnits int, remaining int) {
if pennies%unit == 0 {
return pennies / unit, 0
} else {
numUnits = pennies / unit
remaining = pennies - numUnits*unit
return
}
}

func showChange(pennies int) {
for _, u := range moneyUnits {
var numUnits int
numUnits, pennies = deductChange(pennies, u.value)
if numUnits > 0 {
fmt.Printf("%5d  %s(s)\n", numUnits, u.name)
}
}
if pennies != 0 {
panic("wtf")
}
}

func main() {
showUsage()
for {
cost := getMoney("Cost of item?")
payment := getMoney("Amount of payment?")
if payment == cost {
fmt.Println("Aha! you don't need any change!\n")
} else if payment-cost > 0 {
showChange(int((payment - cost) * 100))
} else {
fmt.Println("\nHey! you need to pay me some more for that!")
}
fmt.Printf("\nAnother item? (enter 'y' or 'n'): ")
var another string
fmt.Scan(&another)
if strings.ToLower(another) == "n" {
break
} else {
fmt.Println()
}
}
fmt.Println("\n\nThank you, come again!\n\n")
}
``````

### Change: Basic Source

``````2 PRINT TAB(33);"CHANGE"
4 PRINT TAB(15);"CREATIVE COMPUTING  MORRISTOWN, NEW JERSEY"
5 PRINT:PRINT:PRINT
6 PRINT "I, YOUR FRIENDLY MICROCOMPUTER, WILL DETERMINE"
8 PRINT "THE CORRECT CHANGE FOR ITEMS COSTING UP TO \$100."
9 PRINT:PRINT
10 PRINT "COST OF ITEM";:INPUT A:PRINT "AMOUNT OF PAYMENT";:INPUT P
20 C=P-A:M=C:IF C<>0 THEN 90
25 PRINT "CORRECT AMOUNT, THANK YOU."
30 GOTO 400
90 IF C>0 THEN 120
95 PRINT "SORRY, YOU HAVE SHORT-CHANGED ME \$";A-P
100 GOTO 10
130 D=INT(C/10)
140 IF D=0 THEN 155
150 PRINT D;"TEN DOLLAR BILL(S)"
155 C=M-(D*10)
160 E=INT(C/5)
170 IF E=0 THEN 185
180 PRINT E;"FIVE DOLLARS BILL(S)"
185 C=M-(D*10+E*5)
190 F=INT(C)
200 IF F=0 THEN 215
210 PRINT F;"ONE DOLLAR BILL(S)"
215 C=M-(D*10+E*5+F)
220 C=C*100
225 N=C
230 G=INT(C/50)
240 IF G=0 THEN 255
250 PRINT G;"ONE HALF DOLLAR(S)"
255 C=N-(G*50)
260 H=INT(C/25)
270 IF H=0 THEN 285
280 PRINT H;"QUARTER(S)"
285 C=N-(G*50+H*25)
290 I=INT(C/10)
300 IF I=0 THEN 315
310 PRINT I;"DIME(S)"
315 C=N-(G*50+H*25+I*10)
320 J=INT(C/5)
330 IF J=0 THEN 345
340 PRINT J;"NICKEL(S)"
345 C=N-(G*50+H*25+I*10+J*5)
350 K=INT(C+.5)
360 IF K=0 THEN 380
370 PRINT K;"PENNY(S)"
380 PRINT "THANK YOU, COME AGAIN."
390 PRINT:PRINT
400 GOTO 10
410 END
``````

### Change: Gameplay

``````\$ go run change.go

The Change-Maker
----------------------------------

Cost of item? : \$4.56
Amount of payment? : \$20
1  Ten Dollar Bill(s)
1  Five Dollar Bill(s)
1  Quarter(s)
1  Dime(s)
1  Nickel(s)
4  Penny(s)

Another item? (enter 'y' or 'n'): y

Cost of item? : \$56.43
Amount of payment? : \$525.50
4  Hundred Dollar Bill(s)
1  Fifty Dollar Bill(s)
1  Ten Dollar Bill(s)
1  Five Dollar Bill(s)
4  One Dollar Bill(s)
1  Nickel(s)
2  Penny(s)

Another item? (enter 'y' or 'n'): n

Thank you, come again!
``````

### Craps: Go Source

``````package main

import (
"fmt"
"math/rand"
"strings"
"time"
)

const (
playerStartingMoney = 100
minimumBetAmount    = 5
diceThrowDelayMs    = 300
pointBreakThrow     = 7
)

const (
rollerPlayer = iota
rollerComputer
)

const (
winStr       = "... and Win!"
loseStr      = "... and Lose!"
rollAgainStr = "... roll again ..."
)

var winningThrows = map[int]bool{
7:  true,
11: true,
}

var losingThrows = map[int]bool{
2:  true,
3:  true,
12: true,
}

func showUsage() {
fmt.Printf("See rules? enter 'y' or 'n' : ")
var choice string
fmt.Scan(&choice)
if strings.ToLower(choice) == "n" {
return
}
fmt.Println("\n       Welcome to CRAPS!    ")
fmt.Println("----------------------------------------")
fmt.Println("\nHere are the rules:")
fmt.Println("- You roll a pair of dice and add up the score for each turn")
fmt.Println("- rolling a 7 or 11 on the first roll wins")
fmt.Println("- rolling a 2, 3 or 12 on the first roll loses")
fmt.Println("- any other number becomes your 'point', and you continue to roll")
fmt.Println("    - if you subsequently roll your 'point' again, you win")
fmt.Println("    - if you roll a 7, you lose")
fmt.Println("- When one of us loses, we switch dice")
fmt.Println("- You start with \$100, and have to bet a minimum of \$5 per turn")
fmt.Println("- You get the first turn")
fmt.Println("- To stop betting, just enter \$0 as your bet amount")
fmt.Println("\n\nThat's it, let's go!\n\n")
}

func getBetMoney(total int) (bet int) {
for {
fmt.Printf("\nYou have \$%d, how much would you like to bet? \$", total)
fmt.Scan(&bet)
if bet > total {
fmt.Println("Hey, you can't bet more than you have!")
} else if bet > 0 && bet < minimumBetAmount {
fmt.Printf("Sorry buddy, you gotta place at least \$%d on the table.\n", minimumBetAmount)
} else {
return
}
}
}

func getDice(subject string) int {
fmt.Printf("%s roll ", subject)
time.Sleep(diceThrowDelayMs * time.Millisecond)
dice1 := 1 + rand.Intn(6)
fmt.Printf("%d ", dice1)
time.Sleep(diceThrowDelayMs * time.Millisecond)
dice2 := 1 + rand.Intn(6)
fmt.Printf("and %d ", dice2)
time.Sleep(diceThrowDelayMs * time.Millisecond)
return dice1 + dice2
}

func playRound(roller int) bool {
subject := "I"
possessive := "My"
if roller == rollerPlayer {
subject = "You"
possessive = "Your"
}

firstThrow := getDice(subject)

if winningThrows[firstThrow] {
fmt.Println(winStr)
return true
}
if losingThrows[firstThrow] {
fmt.Println(loseStr)
return false
}

fmt.Printf("so %s point is %d\n", possessive, firstThrow)
for {
throw := getDice(subject)
if throw == firstThrow {
fmt.Printf("and make %s point!\n", possessive)
return true
}
if throw == pointBreakThrow {
fmt.Println(loseStr)
return false
}
fmt.Println(rollAgainStr)
}
}

func updateMoney(won bool, total, bet int) (newTotal int) {
if won {
newTotal = total + bet
} else {
newTotal = total - bet
}
return
}

func showQuitMessage() {
fmt.Println("\nAh I wish I could quit this easily ... farewell, young gambler!\n")
}

func main() {
showUsage()
rand.Seed(time.Now().Unix())

playerMoney := playerStartingMoney
for {
for {
bet := getBetMoney(playerMoney)
if bet == 0 {
showQuitMessage()
return
}
playerWon := playRound(rollerPlayer)
playerMoney = updateMoney(playerWon, playerMoney, bet)
if !playerWon {
break
}
}

fmt.Println("\n\nOk, my turn now\n")
for {
bet := getBetMoney(playerMoney)
if bet == 0 {
showQuitMessage()
return
}
computerWon := playRound(rollerComputer)
playerMoney = updateMoney(!computerWon, playerMoney, bet)
if !computerWon {
break
}
}
}
}
``````

### Craps: Basic Source

``````5 PRINT TAB(33);"CRAPS"
10 PRINT TAB(15);"CREATIVE COMPUTING  MORRISTOWN, NEW JERSEY"
12 PRINT:PRINT:PRINT
15 LET R=0
20 PRINT"2,3,12 ARE LOSERS; 4,5,6,8,9,10 ARE POINTS; 7,11 ARE NATURAL WINNERS."
21 LET T=1
22 PRINT "PICK A NUMBER AND INPUT TO ROLL DICE";
23 INPUT Z
24 LET X=(RND(0))
25 LET T =T+1
26 IF T<=Z GOTO 24
27 PRINT"INPUT THE AMOUNT OF YOUR WAGER.";
28 INPUT F
30 PRINT "I WILL NOW THROW THE DICE"
40 LET E=INT(7*RND(1))
41 LET S=INT(7*RND(1))
42 LET X=E+S
50 IF X=7 GOTO 180
55 IF X=11 GOTO 180
60 IF X=1 GOTO 40
62 IF X=2 GOTO 195
65 IF X=0 GOTO 40
70 IF X=2 GOTO 200
80 IF X=3 GOTO 200
90 IF X=12 GOTO 200
125 IF X=5 GOTO 220
130 IF X =6 GOTO 220
140 IF X=8 GOTO 220
150 IF X=9 GOTO 220
160 IF X =10 GOTO 220
170 IF X=4 GOTO 220
180 PRINT X "- NATURAL....A WINNER!!!!"
185 PRINT X"PAYS EVEN MONEY, YOU WIN"F"DOLLARS"
190 GOTO 210
195 PRINT X"- SNAKE EYES....YOU LOSE."
196 PRINT "YOU LOSE"F "DOLLARS."
197 LET F=0-F
198 GOTO 210
200 PRINT X " - CRAPS...YOU LOSE."
205 PRINT "YOU LOSE"F"DOLLARS."
206 LET F=0-F
210 LET R= R+F
211 GOTO 320
220 PRINT X "IS THE POINT. I WILL ROLL AGAIN"
230 LET H=INT(7*RND(1))
231 LET Q=INT(7*RND(1))
232 LET O=H+Q
240 IF O=1 GOTO 230
250 IF O=7 GOTO 290
255 IF O=0 GOTO 230
260 IF O=X GOTO 310
270 PRINT O " - NO POINT. I WILL ROLL AGAIN"
280 GOTO 230
290 PRINT O "- CRAPS. YOU LOSE."
291 PRINT "YOU LOSE \$"F
292 F=0-F
293 GOTO 210
300 GOTO 320
310 PRINT X"- A WINNER.........CONGRATS!!!!!!!!"
311 PRINT X "AT 2 TO 1 ODDS PAYS YOU...LET ME SEE..."2*F"DOLLARS"
312 LET F=2*F
313 GOTO 210
320 PRINT " IF YOU WANT TO PLAY AGAIN PRINT 5 IF NOT PRINT 2";
330 INPUT M
331 IF R<0 GOTO 334
332 IF R>0 GOTO 336
333 IF R=0 GOTO 338
334 PRINT "YOU ARE NOW UNDER \$";-R
335 GOTO 340
336 PRINT "YOU ARE NOW AHEAD \$";R
337 GOTO 340
338 PRINT "YOU ARE NOW EVEN AT 0"
340 IF M=5 GOTO 27
341 IF R<0 GOTO 350
342 IF R>0 GOTO 353
343 IF R=0 GOTO 355
350 PRINT"TOO BAD, YOU ARE IN THE HOLE. COME AGAIN."
351 GOTO 360
353 PRINT"CONGRATULATIONS---YOU CAME OUT A WINNER. COME AGAIN!"
354 GOTO 360
355 PRINT"CONGRATULATIONS---YOU CAME OUT EVEN, NOT BAD FOR AN AMATEUR"
360 END
``````

### Craps: Gameplay

``````\$ go run craps.go
See rules? enter 'y' or 'n' : y

Welcome to CRAPS!
----------------------------------------

Here are the rules:
- You roll a pair of dice and add up the score for each turn
- rolling a 7 or 11 on the first roll wins
- rolling a 2, 3 or 12 on the first roll loses
- any other number becomes your 'point', and you continue to roll
- if you subsequently roll your 'point' again, you win
- if you roll a 7, you lose
- When one of us loses, we switch dice
- You start with \$100, and have to bet a minimum of \$5 per turn
- You get the first turn
- To stop betting, just enter \$0 as your bet amount

That's it, let's go!

You have \$100, how much would you like to bet? \$10
You roll 2 and 3 so Your point is 5
You roll 6 and 5 ... roll again ...
You roll 1 and 5 ... roll again ...
You roll 4 and 6 ... roll again ...
You roll 6 and 5 ... roll again ...
You roll 1 and 5 ... roll again ...
You roll 2 and 2 ... roll again ...
You roll 2 and 3 and make Your point!

You have \$110, how much would you like to bet? \$20
You roll 3 and 2 so Your point is 5
You roll 2 and 4 ... roll again ...
You roll 6 and 4 ... roll again ...
You roll 3 and 1 ... roll again ...
You roll 4 and 3 ... and Lose!

Ok, my turn now

You have \$90, how much would you like to bet? \$0

Ah I wish I could quit this easily ... farewell, young gambler!

``````

Coming next: a different kind of gambling game (Blackjack?) and a slightly more involved two-player game (Battleship?)