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

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.

## AsciiDots

```
%$LMRTX
.-$"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
```

out:

```
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

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];
```

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

#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; }

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++

Translation from 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; } } }

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

(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!")

Sample game:

```
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

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

```
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 ] 2bi@ ;
: round ( n -- n-4 )
dup dup .remaining [ drop (round) 4 - round ] unless-zero ;
: nim-game ( -- ) 12 round drop "Computer wins!" print ;
MAIN: nim-game
```

out:

```
-~~==[ 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

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 } } }

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

### Browser Version

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; } }

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

Translated from 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()

out:

```
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

Translated from 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 } } }

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

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.")

Sample game:

```
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

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!")

out:

```
- 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

Translated from 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; }

out:

```
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

Works with Rakudo 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 game:

```
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

Translated from 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
```

out:

```
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

Works with 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!")

out:

```
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

```
#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

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
```

Sample game:

```
──────── 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

[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."

out:

```
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

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!(""); }

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

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.
```

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!
```