Nim Game

From Rosetta Code


Task
Nim Game
You are encouraged to solve this task according to the task description, using any language you may know.

Nim is a simple game where the second player - if they know the trick - will always win.

The game has only 3 rules.

  • start with 12 tokens
  • each player takes 1, 2, or 3 tokens in turn
  • the player who takes the last token wins.


To win every time, the second player simply takes 4 minus the number the first player took. So if the first player takes 1, the second takes 3 - if the first player takes 2, the second should take 2 - and if the first player takes 3, the second player will take 1.


Task

Design a simple Nim game where the human player goes first, and the computer always wins. The game should enforce the rules.

AsciiDots[edit]

 
%$LMRTX
.-$"Nim Dots"-$""-
 
/$_"Number must be "\
T /----~------\ |
*M /---+-*-[o] | |
R [-]\ .>#3-+[>][<]-1#<.| |
.-#12>--^ \"stod "$-#_$-" ekat uoY"_$---/ \--*----*-/ |
.>$_"How many dots would you like to take"---#?---/ |
\X X---------<".3 dna 1 neewteb"$/
/-----*L |
[-]--\ R |
| *-$_"Computer takes "-$_#-$" dots"/
M-*#4[%]
\---/
 
/----------------$"computer wins!"-&
/---~--
*#0[=]
L-------------*---*>$_#-$" dots remaining."-$""
T
 
Output:
Nim Dots

How many dots would you like to take?: 3
You take 3 dots
9 dots remaining.

Computer takes 1 dots
8 dots remaining.

How many dots would you like to take?: 1
You take 1 dots
7 dots remaining.

Computer takes 3 dots
4 dots remaining.

How many dots would you like to take?: 2
You take 2 dots
2 dots remaining.

Computer takes 2 dots
0 dots remaining.

computer wins!

BlooP[edit]

Bloop has no input capabilites, so the game is defined as a procedure, called with 3 numbers (since the game will last only 3 rounds anyhow). The procedure can be called with more numbers - extra parameters are ignored in most implementations I have found. Since there is no easy way to get more inputs, any incorrect values are converted to correct ones.

 
DEFINE PROCEDURE ''DIVIDE'' [A,B]:
BLOCK 0: BEGIN
IF A < B, THEN:
QUIT BLOCK 0;
CELL(0) <= 1;
OUTPUT <= 1;
LOOP AT MOST A TIMES:
BLOCK 2: BEGIN
IF OUTPUT * B = A, THEN:
QUIT BLOCK 0;
OUTPUT <= OUTPUT + 1;
IF OUTPUT * B > A, THEN:
BLOCK 3: BEGIN
OUTPUT <= CELL(0);
QUIT BLOCK 0;
BLOCK 3: END;
CELL(0) <= OUTPUT;
BLOCK 2: END;
BLOCK 0: END.
 
DEFINE PROCEDURE ''MINUS'' [A,B]:
BLOCK 0: BEGIN
IF A < B, THEN:
QUIT BLOCK 0;
LOOP AT MOST A TIMES:
BLOCK 1: BEGIN
IF OUTPUT + B = A, THEN:
QUIT BLOCK 0;
OUTPUT <= OUTPUT + 1;
BLOCK 1: END;
BLOCK 0: END.
 
DEFINE PROCEDURE ''MODULUS'' [A,B]:
BLOCK 0: BEGIN
CELL(0) <= DIVIDE[A,B];
OUTPUT <= MINUS[A,CELL(0) * B];
BLOCK 0: END.
 
DEFINE PROCEDURE ''PLAYER_TURN'' [TOKENS_LEFT, TAKE]:
BLOCK 0: BEGIN
CELL(0) <= TAKE;
 
IF TAKE > 3, THEN:
BLOCK 1: BEGIN
CELL(0) <= MODULUS [TAKE, 3] + 1;
PRINT ['take must be between 1 and 3. setting take to ', CELL(0), '.'];
BLOCK 1: END;
 
IF TAKE < 1, THEN:
BLOCK 2: BEGIN
CELL(0) <= 1;
PRINT ['take must be between 1 and 3. setting take to 1.'];
BLOCK 2: END;
 
OUTPUT <= MINUS [TOKENS_LEFT, CELL(0)];
 
PRINT ['player takes ', CELL(0), ' tokens.'];
PRINT ['tokens remaining: ', OUTPUT];
PRINT [''];
BLOCK 0: END.
 
DEFINE PROCEDURE ''COMPUTER_TURN'' [TOKENS_LEFT]:
BLOCK 0: BEGIN
CELL(0) <= MODULUS [TOKENS_LEFT, 4];
OUTPUT <= MINUS [TOKENS_LEFT, CELL(0)];
 
PRINT ['computer takes ', CELL(0), ' tokens.'];
PRINT ['tokens remaining: ', OUTPUT];
PRINT [''];
BLOCK 0: END.
 
DEFINE PROCEDURE ''PLAY_GAME'' [FST, SEC, THD]:
BLOCK 0: BEGIN
CELL(0) <= FST;
CELL(1) <= SEC;
CELL(2) <= THD;
OUTPUT <= 12;
 
LOOP 3 TIMES:
BLOCK 1: BEGIN
OUTPUT <= PLAYER_TURN [OUTPUT, CELL(0)];
CELL(0) <= CELL(1);
CELL(1) <= CELL(2);
 
OUTPUT <= COMPUTER_TURN [OUTPUT];
BLOCK 1: END;
 
PRINT ['computer wins!'];
BLOCK 0: END.
 
PLAY_GAME [1,4,3];
 
Output:

Sample game:

 > PLAYER TAKES 1 TOKENS.
 > TOKENS REMAINING: 11
 > 
 > COMPUTER TAKES 3 TOKENS.
 > TOKENS REMAINING: 8
 > 
 > TAKE MUST BE BETWEEN 1 AND 3. SETTING TAKE TO 2.
 > PLAYER TAKES 2 TOKENS.
 > TOKENS REMAINING: 6
 > 
 > COMPUTER TAKES 2 TOKENS.
 > TOKENS REMAINING: 4
 > 
 > PLAYER TAKES 3 TOKENS.
 > TOKENS REMAINING: 1
 > 
 > COMPUTER TAKES 1 TOKENS.
 > TOKENS REMAINING: 0
 > 
 > COMPUTER WINS!
=> 0

C[edit]

 
#include <stdio.h>
 
int playerTurn(int numTokens, int take);
int computerTurn(int numTokens);
 
int main(void)
{
printf("Nim Game\n\n");
 
int Tokens = 12;
 
while(Tokens > 0)
{
printf("How many tokens would you like to take?: ");
 
int uin;
scanf("%i", &uin);
 
int nextTokens = playerTurn(Tokens, uin);
 
if (nextTokens == Tokens)
{
continue;
}
 
Tokens = nextTokens;
 
Tokens = computerTurn(Tokens);
}
printf("Computer wins.");
 
return 0;
}
 
int playerTurn(int numTokens, int take)
{
if (take < 1 || take > 3)
{
printf("\nTake must be between 1 and 3.\n\n");
return numTokens;
}
int remainingTokens = numTokens - take;
 
printf("\nPlayer takes %i tokens.\n", take);
printf("%i tokens remaining.\n\n", remainingTokens);
 
return remainingTokens;
}
 
int computerTurn(int numTokens)
{
int take = numTokens % 4;
int remainingTokens = numTokens - take;
 
printf("Computer takes %u tokens.\n", take);
printf("%i tokens remaining.\n\n", remainingTokens);
 
return remainingTokens;
}
 
Output:

Sample game:

Nim Game

How many tokens would you like to take?: 4
Take must be between 1 and 3.

How many tokens would you like to take?: 2
Player takes 2 tokens.
10 tokens remaining.

Computer takes 2 tokens.
8 tokens remaining.

How many tokens would you like to take?: 1
Player takes 1 tokens.
7 tokens remaining.

Computer takes 3 tokens.
4 tokens remaining.

How many tokens would you like to take?: 3
Player takes 3 tokens.
1 tokens remaining.

Computer takes 1 tokens.
0 tokens remaining.

Computer wins.

C++[edit]

Translation of: Go
#include <iostream>
#include <limits>
 
using namespace std;
 
void showTokens(int tokens) {
cout << "Tokens remaining " << tokens << endl << endl;
}
 
int main() {
int tokens = 12;
while (true) {
showTokens(tokens);
cout << " How many tokens 1, 2 or 3? ";
int t;
cin >> t;
if (cin.fail()) {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << endl << "Invalid input, try again." << endl << endl;
} else if (t < 1 || t > 3) {
cout << endl << "Must be a number between 1 and 3, try again." << endl << endl;
} else {
int ct = 4 - t;
string s = (ct > 1) ? "s" : "";
cout << " Computer takes " << ct << " token" << s << endl << endl;
tokens -= 4;
}
if (tokens == 0) {
showTokens(0);
cout << " Computer wins!" << endl;
return 0;
}
}
}
Output:

Sample game:

Tokens remaining 12

  How many tokens 1, 2 or 3? nim

Invalid input, try again.

Tokens remaining 12

  How many tokens 1, 2 or 3? 1
  Computer takes 3 tokens

Tokens remaining 8

  How many tokens 1, 2 or 3? 0

Must be a number between 1 and 3, try again.

Tokens remaining 8

  How many tokens 1, 2 or 3? 2
  Computer takes 2 tokens

Tokens remaining 4

  How many tokens 1, 2 or 3? 3
  Computer takes 1 token

Tokens remaining 0

  Computer wins!

Common Lisp[edit]

 
(defun pturn (curTokens)
(write-string "How many tokens would you like to take?: ")
(setq ans (read))
(setq tokensRemaining (- curTokens ans))
(format t "You take ~D tokens~%" ans)
(printRemaining tokensRemaining)
tokensRemaining)
 
(defun cturn (curTokens)
(setq take (mod curTokens 4))
(setq tokensRemaining (- curTokens take))
(format t "Computer takes ~D tokens~%" take)
(printRemaining tokensRemaining)
tokensRemaining)
 
(defun printRemaining (remaining)
(format t "~D tokens remaining~%~%" remaining))
 
 
(format t "LISP Nim~%~%")
(setq tok 12)
(loop
(setq tok (pturn tok))
(setq tok (cturn tok))
(if (<= tok 0)
(return)))
(write-string "Computer wins!")
 
Output:
LISP Nim

How many tokens would you like to take?: 2
You take 2 tokens
10 tokens remaining

Computer takes 2 tokens
8 tokens remaining

How many tokens would you like to take?: 1
You take 1 tokens
7 tokens remaining

Computer takes 3 tokens
4 tokens remaining

How many tokens would you like to take?: 3
You take 3 tokens
1 tokens remaining

Computer takes 1 tokens
0 tokens remaining

Computer wins!

Crystal[edit]

tokens = 12
 
until tokens <= 0
puts "There are #{tokens} tokens remaining.\nHow many tokens do you take?"
until (input = (gets || "").to_i?) && (1..3).includes? input
puts "Enter an integer between 1 and 3."
end
puts "Player takes #{input} tokens.\nComputer takes #{4-input} tokens."
tokens -= 4
end
 
puts "Computer wins."

Factor[edit]

USING: interpolate io kernel math math.parser sequences ;
IN: rosetta-code.nim-game
 
: get-input ( -- n )
"Number of tokens to take (1, 2, or 3): " write readln
string>number dup { 1 2 3 } member?
[ drop "Invalid move." print get-input ] unless ;
 
: .remaining ( n -- )
nl [I -~~==[ ${} tokens remaining ]==~~-I] nl nl ;
 
: .choice ( str n -- )
dup 1 = "" "s" ? [I ${} took ${} token${}I] nl ;
 
: (round) ( -- )
"You" get-input "Computer" 4 pick - [ .choice ] [email protected] ;
 
: round ( n -- n-4 )
dup dup .remaining [ drop (round) 4 - round ] unless-zero ;
 
: nim-game ( -- ) 12 round drop "Computer wins!" print ;
 
MAIN: nim-game
Output:
-~~==[ 12 tokens remaining ]==~~-

Number of tokens to take (1, 2, or 3): 1
You took 1 token
Computer took 3 tokens

-~~==[ 8 tokens remaining ]==~~-

Number of tokens to take (1, 2, or 3): 3
You took 3 tokens
Computer took 1 token

-~~==[ 4 tokens remaining ]==~~-

Number of tokens to take (1, 2, or 3): 4
Invalid move.
Number of tokens to take (1, 2, or 3): 2
You took 2 tokens
Computer took 2 tokens

-~~==[ 0 tokens remaining ]==~~-

Computer wins!

Go[edit]

package main
 
import (
"bufio"
"fmt"
"os"
"strconv"
)
 
func showTokens(tokens int) {
fmt.Println("Tokens remaining", tokens, "\n")
}
 
func main() {
tokens := 12
scanner := bufio.NewScanner(os.Stdin)
for {
showTokens(tokens)
fmt.Print(" How many tokens 1, 2 or 3? ")
scanner.Scan()
if scerr := scanner.Err(); scerr != nil {
fmt.Println("Error reading standard input:", scerr)
return
}
t, err := strconv.Atoi(scanner.Text())
if err != nil || t < 1 || t > 3 {
fmt.Println("\nMust be a number between 1 and 3, try again.\n")
} else {
ct := 4 - t
s := "s"
if ct == 1 {
s = ""
}
fmt.Print(" Computer takes ", ct, " token", s, "\n\n")
tokens -= 4
}
if tokens == 0 {
showTokens(0)
fmt.Println(" Computer wins!")
return
}
}
}
Output:

Sample game:

Tokens remaining 12 

  How many tokens 1, 2 or 3? 2
  Computer takes 2 tokens

Tokens remaining 8 

  How many tokens 1, 2 or 3? 4

Must be a number between 1 and 3, try again.

Tokens remaining 8 

  How many tokens 1, 2 or 3? 1
  Computer takes 3 tokens

Tokens remaining 4 

  How many tokens 1, 2 or 3? 3
  Computer takes 1 token

Tokens remaining 0 

  Computer wins!

JavaScript[edit]

Browser Version[edit]

This is the easy but dirty way - with prompt for input, and console.log for output. The Nim class was structured so that input and output could be customized, for example to use HTML DOM elements for in and out, instead of the terminal.

 
class Nim {
constructor(tokens, printFun) {
this.startTokens = tokens;
this.tokens = tokens;
this.printFun = printFun;
}
 
playerTurn(take) {
take = Math.round(take);
 
if (take < 1 || take > 3) {
this.printFun("take must be between 1 and 3.\n")
return false;
}
this.tokens -= take;
this.printFun("Player takes " + take + " tokens.");
this.printRemaining()
 
if (this.tokens === 0) {
this.printFun("Player wins!\n");
}
return true;
}
 
computerTurn() {
let take = this.tokens % 4;
this.tokens -= take;
this.printFun("Computer takes " + take + " tokens.");
this.printRemaining();
 
if (this.tokens === 0) {
this.printFun("Computer wins.\n");
}
 
}
 
printRemaining() {
this.printFun(this.tokens + " tokens remaining.\n");
}
}
 
 
let game = new Nim(12, console.log);
while (true) {
if (game.playerTurn(parseInt(prompt("How many tokens would you like to take?")))){
game.computerTurn();
}
if (game.tokens == 0) {
break;
}
}
 
Output:

Sample game:

(prompt) How many tokens would you like to take? 2
Player takes 2 tokens.
10 tokens remaining.

Computer takes 2 tokens.
8 tokens remaining.

(prompt) How many tokens would you like to take? 4
take must be between 1 and 3.

(prompt) How many tokens would you like to take? 0
take must be between 1 and 3.

(prompt) How many tokens would you like to take? 3
Player takes 3 tokens.
5 tokens remaining.

Computer takes 1 tokens.
4 tokens remaining.

(prompt) How many tokens would you like to take? 1
Player takes 1 tokens.
3 tokens remaining.

Computer takes 3 tokens.
0 tokens remaining.

Computer wins.

Julia[edit]

Translation of: Perl 6
function nimgame()
tcount = 12
takenum = 0
while true
while true
permitted = collect(1:min(3,tcount))
println("$tcount tokens remain.\nHow many do you take ($permitted)? ")
takenum = parse(Int, strip(readline(stdin)))
if takenum in permitted
break
end
end
tcount -= 4
println("Computer takes $(4 - takenum). There are $tcount tokens left.")
if tcount < 1
println("Computer wins as expected.")
break
end
end
end
 
nimgame()
 
Output:
12 tokens remain.
How many do you take ([1, 2, 3])?
3
Computer takes 1. There are 8 tokens left.
8 tokens remain.
How many do you take ([1, 2, 3])?
2
Computer takes 2. There are 4 tokens left.
4 tokens remain.
How many do you take ([1, 2, 3])?
1
Computer takes 3. There are 0 tokens left.
Computer wins as expected.

Kotlin[edit]

Translation of: Go
// Version 1.3.21
 
fun showTokens(tokens: Int) {
println("Tokens remaining $tokens\n")
}
 
fun main() {
var tokens = 12
while (true) {
showTokens(tokens)
print(" How many tokens 1, 2 or 3? ")
var t = readLine()!!.toIntOrNull()
if (t == null || t < 1 || t > 3) {
println("\nMust be a number between 1 and 3, try again.\n")
} else {
var ct = 4 - t
var s = if (ct > 1) "s" else ""
println(" Computer takes $ct token$s\n")
tokens -= 4
}
if (tokens == 0) {
showTokens(0)
println(" Computer wins!")
return
}
}
}
Output:

Sample game:

Tokens remaining 12

  How many tokens 1, 2 or 3? 3
  Computer takes 1 token

Tokens remaining 8

  How many tokens 1, 2 or 3? nim

Must be a number between 1 and 3, try again.

Tokens remaining 8

  How many tokens 1, 2 or 3? 2
  Computer takes 2 tokens

Tokens remaining 4

  How many tokens 1, 2 or 3? 1
  Computer takes 3 tokens

Tokens remaining 0

  Computer wins!

Lua[edit]

 
tokens = 12
 
print("Nim Game\n")
print("Starting with " .. tokens .. " tokens.\n\n")
 
function printRemaining()
print(tokens .. " tokens remaining.\n")
end
 
function playerTurn(take)
take = math.floor(take)
if (take < 1 or take > 3) then
print ("\nTake must be between 1 and 3.\n")
return false
end
 
tokens = tokens - take
 
print ("\nPlayer takes " .. take .. " tokens.")
printRemaining()
return true
end
 
function computerTurn()
take = tokens % 4
tokens = tokens - take
 
print("Computer takes " .. take .. " tokens.")
printRemaining()
end
 
while (tokens > 0) do
io.write("How many tokens would you like to take?: ")
if playerTurn(io.read("*n")) then
computerTurn()
end
end
 
print ("Computer wins.")
 
Output:

Sample game output:

Nim Game

Starting with 12 tokens.


How many tokens would you like to take?: 3
Player takes 3 tokens.
9 tokens remaining.

Computer takes 1 tokens.
8 tokens remaining.

How many tokens would you like to take?: 4
Take must be between 1 and 3.

How many tokens would you like to take?: 1
Player takes 1 tokens.
7 tokens remaining.

Computer takes 3 tokens.
4 tokens remaining.

How many tokens would you like to take?: 2
Player takes 2 tokens.
2 tokens remaining.

Computer takes 2 tokens.
0 tokens remaining.

Computer wins.

Nim[edit]

import strutils
import terminal
 
var tokens = 12
 
styledEcho(styleBright, "Nim in Nim\n")
 
proc echoTokens() =
styledEcho(styleBright, "Tokens remaining: ", resetStyle, $tokens, "\n")
 
proc player() =
var take = '0'
styledEcho(styleBright, "- Your turn -")
echo "How many tokens will you take?"
while true:
stdout.styledWrite(styleDim, "Take (1–3): ", resetStyle)
take = getch()
stdout.write(take, '\n')
if take in {'1'..'3'}:
tokens -= parseInt($take)
break
else:
echo "Please choose a number between 1 and 3."
echoTokens()
 
proc computer() =
styledEcho(styleBright, "- Computer's turn -")
let take = tokens mod 4
tokens -= take
styledEcho("Computer took ", styleBright, $take, " ",
if take == 1: "token"
else: "tokens")
echoTokens()
 
while tokens > 0:
player()
computer()
 
styledEcho(styleBright, "Computer wins!")
Output:
- Your turn -
How many tokens will you take?
Take (1–3): 1
Tokens remaining: 11

- Computer's turn -
Computer took 3 tokens
Tokens remaining: 8

- Your turn -
How many tokens will you take?
Take (1–3): 2
Tokens remaining: 6

- Computer's turn -
Computer took 2 tokens
Tokens remaining: 4

- Your turn -
How many tokens will you take?
Take (1–3): 3
Tokens remaining: 1

- Computer's turn -
Computer took 1 token
Tokens remaining: 0

Computer wins!

Perl[edit]

Translation of: Perl 6
use strict;
use warnings;
use feature 'say';
 
my $tokens = 12;
say "$tokens tokens remaining.\n";
 
while (1) {
print "How many tokens do you want to remove; 1, 2 or 3? : ";
(my $player = <>) =~ s/\s//g;
say "Nice try. $tokens tokens remaining.\n" and next
unless $player =~ /^[123]$/;
$tokens -= 4;
say "Computer takes @{[4 - $player]}.\n$tokens tokens remaining.\n";
say "Computer wins." and last
if $tokens <= 0;
}
Output:
12 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 3
Computer takes 1.
8 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : -1
Nice try. 8 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 2
Computer takes 2.
4 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 1
Computer takes 3.
0 tokens remaining.

Computer wins.

Perl 6[edit]

Works with: Rakudo version 2019.03
say my $tokens = 12, " tokens remaining.\n";
 
loop {
my $player = trim prompt "How many tokens do you want to remove; 1, 2 or 3? : ";
say "Nice try. $tokens tokens remaining.\n" and
next unless $player eq any <1 2 3>;
$tokens -= 4;
say "Computer takes {4 - $player}.\n$tokens tokens remaining.\n";
say "Computer wins." and last if $tokens <= 0;
}
Sample output:
12 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 3
Computer takes 1.
8 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 6
Nice try. 8 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : G
Nice try. 8 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 2
Computer takes 2.
4 tokens remaining.

How many tokens do you want to remove; 1, 2 or 3? : 1
Computer takes 3.
0 tokens remaining.

Computer wins.

Phix[edit]

Translation of: Perl_6
integer tokens = 12, player = 0
 
while true do
printf(1,"%2d tokens remaining. ",tokens)
if tokens=0 then printf(1,"Computer wins.\n") exit end if
printf(1,"How many tokens do you want to remove; 1, 2, or 3?:")
while player<1 or player>3 do player=getc(0)-'0' end while
printf(1,"%d. Computer takes %d.\n",{player,4-player})
tokens -= 4; player = 0
end while
Output:
12 tokens remaining. How many tokens do you want to remove; 1, 2, or 3?:1. Computer takes 3.
 8 tokens remaining. How many tokens do you want to remove; 1, 2, or 3?:2. Computer takes 2.
 4 tokens remaining. How many tokens do you want to remove; 1, 2, or 3?:3. Computer takes 1.
 0 tokens remaining. Computer wins.

Python[edit]

Works on Python 3

 
print("Py Nim\n")
 
def getTokens(curTokens):
global tokens
 
print("How many tokens would you like to take? ", end='')
take = int(input())
 
if (take < 1 or take > 3):
print("Number must be between 1 and 3.\n")
getTokens(curTokens)
return
 
tokens = curTokens - take
print(f'You take {take} tokens.')
print(f'{tokens} tokens remaining.\n')
 
def compTurn(curTokens):
global tokens
 
take = curTokens % 4
tokens = curTokens - take
print (f'Computer takes {take} tokens.')
print (f'{tokens} tokens remaining.\n')
 
 
tokens = 12
while (tokens > 0):
getTokens(tokens)
compTurn(tokens)
 
print("Computer wins!")
 
Output:
Py Nim

How many tokens would you like to take? 2
You take 2 tokens.
10 tokens remaining.

Computer takes 2 tokens.
8 tokens remaining.

How many tokens would you like to take? 1
You take 1 tokens.
7 tokens remaining.

Computer takes 3 tokens.
4 tokens remaining.

How many tokens would you like to take? 3
You take 3 tokens.
1 tokens remaining.

Computer takes 1 tokens.
0 tokens remaining.

Computer wins!

Racket[edit]

 
#lang racket
 
(define (print-remaining tokens-remaining)
(printf "~a tokens remain.\n" tokens-remaining))
 
(define (read-tokens)
(define num (read))
(cond
[(and (natural? num) (< num 4)) num]
[else
(display "Please enter a number between 1 to 3\n")
(read-tokens)]))
 
(define (pturn tokens-remaining)
(cond
[(not (zero? tokens-remaining))
(print-remaining tokens-remaining)
(display "Your turn. How many tokens? ")
(define n (read-tokens))
(cturn (- tokens-remaining n) n)]
[else (display "Computer wins!")]))
 
 
(define (cturn tokens-remaining p-took)
(cond
[(not (zero? tokens-remaining))
(print-remaining tokens-remaining)
(define c-take (- 4 p-took))
(printf "Computer takes ~a tokens\n" c-take)
(pturn (- tokens-remaining c-take))]
[else (display "You win!")]))
 
(pturn 12)
 

REXX[edit]

Programming notes:   extra error checking was done with specific informative error messages.   Also included was a method of quitting the game.   The number of (starting) tokens   (the pot)   can be specified on the command line,   the default is   12.

/*REXX program plays the NIM game with a human opponent; the pot size can be specified. */
pad= copies('─', 8) /*eyecatcher literal used in messages. */
parse arg pot _ . 1 __ /*obtain optional argument from the CL.*/
if pot=='' | pot=="," then pot= 12 /*Not specified? Then use the default.*/
if _\=='' then do; call ser "Too many arguments entered: " __; exit 13; end
if \isNum(pot) then do; call ser "argument isn't numeric: " pot; exit 13; end
if \isInt(pot) then do; call ser "argument isn't an integer: " pot; exit 13; end
if pot<4 then do; call ser "The pot number is too small: " pot; exit 13; end
if pot>100 then do; call ser "The pot number is too large: " pot; exit 13; end
pot= pot/1 /*normalize the pot (number). */
 
do forever; call show pot
do until ok; ok=1; say
say pad "How many tokens do you want to take away (1, 2, or 3) (or QUIT)?"
parse pull t _ . 1 q 1 __; upper q; say
if abbrev('QUIT',q,1) then do; say pad 'Quitting.'; exit 1; end
if t='' then call ser "No arguments entered."
if _\=='' then call ser "Too many arguments entered: " __
if \isNum(t) then call ser "Argument isn't numeric: " t
if \isInt(t) then call ser "Argument isn't an integer: " t
if t<1 then call ser "Argument can't be less than 1: " t
if t>3 then call ser "Argument can't be greater than 3: " t
end /*while*/
t= t/1 /*Normalize the number: 001 2. +3 */
#= 4-t /*calculate the computer's take─away. */
say pad "The computer takes " # " token"s(#).
pot= pot - t - # /*calculate the number of tokens in pot*/
if pot==0 then do; say pad 'No tokens left.' /*No tokens left in the pot? */
say pad "The computer wins!" /*Display a braggart message.*/
exit /*exit this computer program.*/
end
end /*forever*/ /*keep looping until there's a winner. */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
isNum: return datatype( arg(1), 'N') /*verify that the arg is a number. */
isInt: return datatype( arg(1), 'W') /* " " " " " an integer. */
show: say; say pad "Tokens remaining: " arg(1)' ' pad; say; return
s: if arg(1)==1 then return arg(3); return word(arg(2) 's',1)
ser: if ok then say pad '***error***' arg(1); ok= 0; return
output   when using the default input:
──────── Tokens remaining:  12  ────────


──────── How many tokens do you want to take away  (1, 2, or 3)    (or QUIT)?
2                                            ◄■■■■■■■■■■■ user input                                             

──────── The computer takes  2  tokens.

──────── Tokens remaining:  8  ────────


──────── How many tokens do you want to take away  (1, 2, or 3)    (or QUIT)?
3                                            ◄■■■■■■■■■■■ user input

──────── The computer takes  1  token.

──────── Tokens remaining:  4  ────────


──────── How many tokens do you want to take away  (1, 2, or 3)    (or QUIT)?
1                                            ◄■■■■■■■■■■■ user input 

──────── The computer takes  3  tokens.
──────── No tokens left.
──────── The computer wins!


Ruby[edit]

[12, 8, 4].each do |remaining|
puts "There are #{remaining} dots.\nHow many dots would you like to take? "
unless (num=gets.to_i).between?(1, 3)
puts "Please enter one of 1, 2 or 3"
redo
end
puts "You took #{num} dots, leaving #{remaining-num}.\nComputer takes #{4-num}.\n\n"
end
 
puts "Computer took the last and wins."
 
Output:
There are 12 dots.
How many dots would you like to take? 
foo
Please enter one of 1, 2 or 3
There are 12 dots.
How many dots would you like to take? 
1
You took 1 dots, leaving 11.
Computer takes 3.

There are 8 dots.
How many dots would you like to take? 
3
You took 3 dots, leaving 5.
Computer takes 1.

There are 4 dots.
How many dots would you like to take? 
2
You took 2 dots, leaving 2.
Computer takes 2.

Computer took the last and wins.

Rust[edit]

use std::io;
 
fn main() {
let mut tokens = 12;
println!("Nim game");
println!("Starting with {} tokens.", tokens);
println!("");
 
loop {
tokens = p_turn(&tokens);
print_remaining(&tokens);
tokens = c_turn(&tokens);
print_remaining(&tokens);
 
if tokens == 0 {
println!("Computer wins!");
break;
}
}
}
 
fn p_turn(tokens: &i32) -> i32 {
loop { //try until we get a good number
println!("How many tokens would you like to take?");
 
let mut take = String::new();
io::stdin().read_line(&mut take)
.expect("Sorry, I didn't understand that.");
 
let take: i32 = match take.trim().parse() {
Ok(num) => num,
Err(_) => {
println!("Invalid input");
println!("");
continue;
}
};
 
if take > 3 || take < 1 {
println!("Take must be between 1 and 3.");
println!("");
continue;
}
 
return tokens - take;
}
}
 
fn c_turn(tokens: &i32) -> i32 {
let take = tokens % 4;
 
println!("Computer takes {} tokens.", take);
 
return tokens - take;
}
 
fn print_remaining(tokens: &i32) {
println!("{} tokens remaining.", tokens);
println!("");
}
 
Output:

sample game:

Nim game
Starting with 12 tokens.

How many tokens would you like to take?
foo
Invalid input

How many tokens would you like to take?
3
9 tokens remaining.

Computer takes 1 tokens.
8 tokens remaining.

How many tokens would you like to take?
5
Take must be between 1 and 3.

How many tokens would you like to take?
2
6 tokens remaining.

Computer takes 2 tokens.
4 tokens remaining.

How many tokens would you like to take?
1
3 tokens remaining.

Computer takes 3 tokens.
0 tokens remaining.

Computer wins!

Smalltalk[edit]

Works with: GNU Smalltalk
 
Object subclass: Nim [
| tokens |
<comment: 'I am a game of nim'>
Nim class >> new [
<category: 'instance creation'>
^(super new) init: 12
]
 
init: t [
<category: 'instance creation'>
tokens := t.
^self
]
 
 
pTurn [
| take |
<category: 'gameplay'>
Transcript nextPutAll: 'How many tokens will you take?: '.
take := (stdin nextLine) asNumber.
((take < 1) | (take > 3))
ifTrue: [Transcript nextPutAll: 'Invalid input';nl;nl. self pTurn]
ifFalse: [tokens := tokens - take]
]
 
cTurn [
| take |
<category: 'gameplay'>
take := tokens - (4 * (tokens // 4)). "tokens % 4"
Transcript nextPutAll: 'Computer takes '.
take printOn: Transcript.
Transcript nextPutAll: ' tokens';nl.
tokens := tokens - take
]
 
mainLoop [
<category: 'main loop'>
Transcript nextPutAll: 'Nim game';nl.
Transcript nextPutAll: 'Starting with '.
tokens printOn: Transcript.
Transcript nextPutAll: ' tokens';nl;nl.
1 to: 3 do: [ :n | "The computer always wins on the 3rd turn"
self pTurn.
self printRemaining.
self cTurn.
self printRemaining.
(tokens = 0)
ifTrue:[Transcript nextPutAll: 'Computer wins!';nl. ^0]
]
]
 
printRemaining [
<category: 'information'>
tokens printOn: Transcript.
Transcript nextPutAll: ' tokens remaining';nl;nl
]
]
 
g := Nim new.
g mainLoop.
 
Output:

sample game:

Nim game
Starting with 12 tokens

How many tokens will you take?: foo
Invalid input

How many tokens will you take?: 3
9 tokens remaining

Computer takes 1 tokens
8 tokens remaining

How many tokens will you take?: 4
Invalid input

How many tokens will you take?: 2
6 tokens remaining

Computer takes 2 tokens
4 tokens remaining

How many tokens will you take?: 1
3 tokens remaining

Computer takes 3 tokens
0 tokens remaining

Computer wins!