The determined Real Programmer can write Fortran programs in any language.

from Real Programmers Don't Use Pascal

Your task is to write program in your programming language of choice, but you are allowed to use only another language. That is, throw away all coding conventions from one language and replace them with coding conventions from other language. The more the better. Make your program look as if it was written in another language.

For example, Python fan who hates Java could write following Python program in Java:

void my_function()                                                             {
    int i = 9                                                                  ;
    while(i>0)                                                                 {
        System.out.println("Hello!")                                           ;
        i = i - 1                                                              ;}}

Pascal enthusiast forced to use C could write this:

#define begin {
#define end }
#define then
#define writeln(str) puts(str)

if (i == 10) then
    writeln("I hate C");

You have to write complete program. The program desn't have to do anything useful.

Good Luck. This is a popularity contest so the code with the most votes wins!

  • 1
    \$\begingroup\$ @m.buettner create your file with the extension .litcoffee. It might help. \$\endgroup\$ Commented Mar 20, 2014 at 22:53
  • \$\begingroup\$ A little long (and previously-written; and not self-contained) for an answer, but: Postscript scanner in Postscript in C. \$\endgroup\$ Commented Mar 21, 2014 at 4:36
  • 53
    \$\begingroup\$ I don't think you (or the majority of the answers) understand the point of the quote. It's not that a Real Programmer writes code that looks lexically like Fortran even though he's writing in Pascal or LISP: it's that he applies a Fortran way of thinking even when writing in Pascal or LISP; e.g. "As all Real Programmers know, the only useful data structure is the Array.". Great answers would be procedural code in Prolog, functional code in C, object-oriented code in Pascal. \$\endgroup\$ Commented Mar 21, 2014 at 11:10
  • 1
    \$\begingroup\$ I hope someone's gonna do a Lisp dialect in, well, anything but another Lisp dialect... \$\endgroup\$
    – itsjeyd
    Commented Mar 21, 2014 at 21:23
  • 7
    \$\begingroup\$ @itsjeyd Greenspun's Tenth Rule Of Programming: "Any sufficiently complicated C or Fortran program contains an ad-hoc, informally-specified, bug-ridden, slow implementation of half of CommonLisp." \$\endgroup\$ Commented Mar 25, 2014 at 17:38

36 Answers 36


C in C++

#include <stdio.h>

int main(int argc, char** argv)
        printf("Hello world!\n");
        return 0;
  • 63
    \$\begingroup\$ I see what you did there;) \$\endgroup\$ Commented Mar 21, 2014 at 10:38
  • 29
    \$\begingroup\$ Well, that's a cheap trick, seeing as C++ is 'backwards compatible' with C. \$\endgroup\$ Commented Mar 21, 2014 at 23:29
  • 5
    \$\begingroup\$ @AlexM. I think it would be more in the spirit of the question if this was a longer (procedural) example which would clearly benefit from using some classes and which uses other C idioms where some STL goodness would be much more reasonable (say char* instead of std::string). \$\endgroup\$ Commented Mar 22, 2014 at 10:48
  • 47
    \$\begingroup\$ Valid in C, C++, Objective-C, and Objective-C++! What a wonderfully polyglot answer. \$\endgroup\$
    – nneonneo
    Commented Mar 23, 2014 at 0:23
  • 7
    \$\begingroup\$ @BenJackson Psh, real C programmers use char *argv[]! \$\endgroup\$
    – Thomas
    Commented Mar 26, 2014 at 2:14

x86 assembly in GNU C

No, I didn't just use the asm keyword, since the question established this is for real programmers... this should run fine on ARM.

(Just to prove the point, I didn't "write" the assembly at all - it's the output produced by GCC Clang (503.0.38) for the commented code at the top, blindly translated into macros.)

This only works in 32-bit mode. That's fine since real programmers code to the word size anyway.

#include <stdio.h>
#include <stdint.h>
int fac(int x) {
    if (x < 1) return 1; else return x * fac(x - 1);

int fib(int x) {
    if (x < 2) return x; else return fib(x - 1) + fib(x - 2);

int main(void) {
    int a = fib(10), b = fac(10);
    printf("%d %d\n", a, b);
    return 0;

typedef union REG {
    intptr_t i; int _i; void * v; union REG * r;
} REG;

#define LPAREN (
#define RPAREN )
#define MACRO(N) ); N##_MACRO LPAREN

#define push MACRO(PUSH)
#define pop  MACRO(POP)
#define mov  MACRO(MOV)
#define sub  MACRO(SUB)
#define add  MACRO(ADD)
#define imul MACRO(IMUL)
#define cmp  MACRO(CMP)
#define jge  MACRO(JGE)
#define jmp  MACRO(JMP)
#define call MACRO(CALL)
#define ret  MACRO(RET) _
#define label MACRO(LABEL)

#define NO_OP(X) 

#define PUSH_MACRO(VAL) *(esp -= 4) = (REG)(VAL)
#define POP_MACRO(DST) (DST) = (typeof(DST))(esp->i); esp += 4
#define MOV_MACRO(VAL, DST) (DST) = (typeof(DST))((REG)VAL).i;
    (DST) = (typeof(DST))(((REG)DST).i - ((REG)VAL).i)
#define ADD_MACRO(VAL, DST) DST = (typeof(DST))(((REG)DST).i + ((REG)VAL).i); \
    ZF = ((REG)DST).i == 0; OF = 0; SF = ((REG)DST).i < 0
#define IMUL_MACRO(VAL, DST) DST = (typeof(DST))(((REG)DST).i * ((REG)VAL).i); \
    ZF = ((REG)DST).i == 0; OF = 0; SF = ((REG)DST).i < 0
#define CMP_MACRO(L, R) CMP_MACRO_(((REG)L).i, ((REG)R).i)
#define CMP_MACRO_(L, R) (OF = 0, ZF = L == R, SF = (R - L) < 0)
#define JGE_MACRO(TGT) if (SF == OF) { goto TGT; } else {}
#define JMP_MACRO(TGT) goto TGT;
    goto PROC; case CTR - STARTIP:
#define RET_MACRO(_) eip = esp->i; esp += 4; if (eip) { continue; } else { goto *finalreturn; }

#define MY_ASM(X) do { const int STARTIP = __COUNTER__; \
    switch(eip) { case 0: MY_ASM_1 X } } while (1);
#define MY_ASM_2(X) X

#define CAT(L, R) _CAT(L, R)
#define _CAT(L, R) L##R

#define callASM(F) callASM_(F, CAT(_TMP_, __COUNTER__))
#define callASM_(F, LABEL) (({ PUSH_MACRO(0); stackbase = esp; finalreturn = &&LABEL; \
    goto F; LABEL:; }), (intptr_t)eax)

const int STACKSIZE = 4096;
REG callstack[STACKSIZE], * stackbase;
REG * eax, * ecx, * edx, * ebx, * esi, * edi, * esp, * ebp;
int SF, ZF, OF, eip; void * finalreturn;

int main(void) {
    eax = ecx = edx = ebx = esi = edi = esp = ebp = &callstack[STACKSIZE - 1];
    eip = 0;
    finalreturn = &&TOP; TOP:

    int a = callASM(_fac);
    int b = callASM(_fib);

    printf("%d %d\n", a, b);
    return 0;

    label _fac:                                   // @fac
        push ebp
        mov esp, ebp
        sub 24, esp
        mov 8[ebp], eax
        mov eax, (-8)[ebp]
        cmp 1, (-8)[ebp]
        jge LBB0_2
        mov 1, (-4)[ebp]
        jmp LBB0_3
    label LBB0_2:
        mov (-8)[ebp], eax
        mov (-8)[ebp], ecx
        sub 1, ecx
        mov ecx, *esp
        mov eax, (-12)[ebp]         // 4-byte Spill
        call _fac
        mov (-12)[ebp], ecx         // 4-byte Reload
        imul eax, ecx
        mov ecx, (-4)[ebp]
    label LBB0_3:
        mov (-4)[ebp], eax
        add 24, esp
        pop ebp

    label _fib:                                   // @fib
        push ebp
        mov esp, ebp
        sub 24, esp
        mov 8[ebp], eax
        mov eax, (-8)[ebp]
        cmp 2, (-8)[ebp]
        jge LBB1_2
        mov (-8)[ebp], eax
        mov eax, (-4)[ebp]
        jmp LBB1_3
    label LBB1_2:
        mov (-8)[ebp], eax
        sub 1, eax
        mov eax, *esp
        call _fib
        mov (-8)[ebp], ecx
        sub 2, ecx
        mov ecx, *esp
        mov eax, (-12)[ebp]         // 4-byte Spill
        call _fib
        mov (-12)[ebp], ecx         // 4-byte Reload
        add eax, ecx
        mov ecx, (-4)[ebp]
    label LBB1_3:
        mov (-4)[ebp], eax
        add 24, esp
        pop ebp

Just look at all those casts. Casts mean I'm a realer programmer than the compiler, right?

  • 8
    \$\begingroup\$ +1, that's... twisted. ;) I really like how you handled call, in particular. \$\endgroup\$ Commented Mar 22, 2014 at 19:02
  • 2
    \$\begingroup\$ Wow. That's a great piece of work. \$\endgroup\$ Commented Mar 24, 2014 at 10:37
  • \$\begingroup\$ I had an assembler for the C64 that worked sort of like this. It added BASIC keywords for all the 6510 instructions and I remember you wrapped for pass=1:3...next around it. Executing it in the BASIC interpreter assembled it. \$\endgroup\$ Commented Mar 25, 2014 at 3:27
  • 5
    \$\begingroup\$ This is pure poetry. \$\endgroup\$ Commented Mar 27, 2014 at 22:46
  • 1
    \$\begingroup\$ This is tough man, the compiler sure is amazed. \$\endgroup\$ Commented Mar 28, 2014 at 10:30

English in C

#include <stdio.h>
#define This
#define program     int main() {
#define aims
#define to
#define output      printf(
#define some
#define example
#define text(a)     #a
#define the
#define screen      "\n");
#define it          
#define also
#define will
#define calculate   ;int a = 
#define result
#define of
#define and
#define print       ; printf("%d\n", a);
#define seriously   return 0; }

This program aims to output some example text (Hello) to the screen;
it also will calculate the result of 3 + 4 and print the result; seriously

Any ideas to eliminate the ;?

  • 19
    \$\begingroup\$ Seriously, you guys. \$\endgroup\$ Commented Mar 25, 2014 at 19:57
  • 2
    \$\begingroup\$ why define the twice? \$\endgroup\$ Commented Mar 25, 2014 at 23:01
  • 17
    \$\begingroup\$ better safe than sorry ;-) \$\endgroup\$
    – urzeit
    Commented Mar 26, 2014 at 7:01
  • 22
    \$\begingroup\$ Now make it a haiku. \$\endgroup\$ Commented Mar 27, 2014 at 22:48
  • 1
    \$\begingroup\$ Can you #define . ; \$\endgroup\$
    – mbomb007
    Commented Mar 21, 2016 at 18:33

I think the brilliant Lennart Augustsson has already won this twice.

First, here's an example of his "weekend hack" implementation of BASIC as a Haskell Monadic DSL, from 2009:

import BASIC

main = runBASIC' $ do

    10 LET I =: 1
    20 LET S =: 0
    30 LET S =: S + 1/I
    40 LET I =: I + 1
    50 IF I <> 100000000 THEN 30
    60 PRINT "Almost infinity is"
    70 PRINT S
    80 END

It works by overloading the number type. The line numbers are really functions that accept arguments. The rest of the line is arguments to the function. The function returns a representation of the Abstract Syntax Tree for the BASIC interpreter to go to work on.

I also recommend you check out Augustsson's entry to the 2006 International Obfuscated C Contest, in which he managed to squeeze into 4k:

  • A bytecode interpreter, written in a subset of C (which he calls Obfuscated C).
  • An Obfuscated C -> bytecode compiler, written in bytecode.

They can share the same file because the bytecode is placed inside C comments.

It's a few years since I followed Augustsson's work, so there may well be other brilliant things he's come up with since then....

  • 2
    \$\begingroup\$ It's Augustsson, not Augustssen. \$\endgroup\$ Commented Mar 23, 2014 at 12:56
  • \$\begingroup\$ @HansLundmark Thanks. Fixed it. \$\endgroup\$
    – Pitarou
    Commented Mar 24, 2014 at 2:23

Brainfuck in JavaScript

Javascript is a difficult language ! Let us use Brainfuck, a more understandable language :o)


//write your easy code below


//end of easy code

.replace(/^/,'var a=new Array(1000).join(\'0\').split(\'\'),i=500,o=\'\',u=prompt(\'Enter input if needed\'),j=0;')

I guess I wrote a brainfuck interpreter in javascript.

The example above simply ouputs Hello World! and ignore the input (no , symbol).
But that works with inputs too ! For example, try ,+>,+>,+>,+<<<.>.>.>. and type golf in the dialog. It will ouputs the next characters in ASCII table : hpmg

EDIT : Short explanation for people who don't know brainfuck.
Imagine an infinite array of integers a initialized to zero everywhere, a pointer on one element of this array i, and a user input u.
Brainfuck is really easy to learn but difficult to write :

  • + increments to current value : a[i]++
  • - decrements it : a[i]--
  • > makes to pointer points the next element : i++
  • < the previous : i--
  • [ and ] define a loop which breaks when current value is zero : while (a[i]) { ... }
  • . print the current element : String.fromCharCode(a[i])
  • , sets the current element with user input : u.charCodeAt(...)
  • 22
    \$\begingroup\$ +1 for the humour in stating that brainfuck is more understandable than JavaScript. \$\endgroup\$ Commented Mar 21, 2014 at 23:27
  • \$\begingroup\$ Are you sure that the Brainfuck characters inside of the replace statements don't affect the program? \$\endgroup\$
    – ashastral
    Commented Mar 22, 2014 at 23:41
  • 3
    \$\begingroup\$ @fra This file isn't a brainfuck program, it's a javascript program that contains a brainfuck program that's converted to javascript at runtime. \$\endgroup\$ Commented Mar 23, 2014 at 1:29
  • 3
    \$\begingroup\$ Well, --i faster than i-- ? Seems false since years : jsperf.com/decrementgolf. \$\endgroup\$
    – Michael M.
    Commented Mar 23, 2014 at 18:55
  • 4
    \$\begingroup\$ This not only is very creative submission to the contest, but also explains brainfuck syntax very clearly. +10 if I could! \$\endgroup\$
    – SebastianH
    Commented Mar 26, 2014 at 15:25

PHP and Javascript

This is a polyglot:

You can run this code in both languages:

    function printf(){
        return $a.length;

    function strtoupper($s){return $s['toUpperCase']();}

    function count($a){return $a['length'];}

printf('this is cool!');



The trick here is that Javascript uses escape sequences in strings starting with ' and ".
On the other hand, PHP only uses escape sequences in strings starting with " and <<<.

Then, we declare the function printf, which is similar to print but outputs a formated string in PHP.

PHP requires that vars start with $, while Javascript simply allows.

  • \$\begingroup\$ Nobody's using Array(…) in JS, and it's clearly array(…) in PHP. […] would be far better ;) ! \$\endgroup\$
    – Blackhole
    Commented Mar 23, 2014 at 0:49
  • 12
    \$\begingroup\$ I don't care if people use Array() in JS or not: I care that I have a TRUE polyglot. I'm making one of the worst JS crimes with this code but all I want is that it runs and does the exact same thing in both, but looking like JS and PHP at the same time. \$\endgroup\$ Commented Mar 23, 2014 at 18:29
  • \$\begingroup\$ And btw, [...] is invalid in PHP <5.4.0, which is bad....... If I throw this into PHP 4, 5 or Javascript, I expect it to work, instead of giving syntax errors everywhere. \$\endgroup\$ Commented Mar 23, 2014 at 20:31
  • 2
    \$\begingroup\$ If you want your code to look like JS, you must use […], which seems pretty standard in PHP, and therefore is OK for your goal. And by the way, PHP < 5.4? Time to update, guy… \$\endgroup\$
    – Blackhole
    Commented Mar 23, 2014 at 20:48
  • 8
    \$\begingroup\$ Compatibility is more important than "looks". And Array is the RIGHT name of the Array object's constructor. Basicly, using [] is the same as Array(). I don't see anything bad with it. But I have one simple question: Works? (btw, I have to use php 5.3.28 at work.) \$\endgroup\$ Commented Mar 23, 2014 at 21:29

Brainfuck in JS

  • 12
    \$\begingroup\$ I don't see any brainfuck here. Not even a single char in ><,.- \$\endgroup\$
    – Michael M.
    Commented Mar 21, 2014 at 13:11
  • 8
    \$\begingroup\$ @Michael: Who said it isn't a program that makes an infinite loop? \$\endgroup\$
    – null
    Commented Mar 21, 2014 at 16:12
  • 19
    \$\begingroup\$ is this JSF*ck? \$\endgroup\$
    – user16402
    Commented Mar 22, 2014 at 19:05
  • 8
    \$\begingroup\$ How on Earth does it do that? \$\endgroup\$
    – nandhp
    Commented Mar 26, 2014 at 15:57
  • 4
    \$\begingroup\$ Oo. Somebody finally did this. I spent some time trying to figure out how to write a JS program using only the characters +![]() but never could quite figure it out. I need to analyze this when I have time... \$\endgroup\$ Commented Mar 31, 2014 at 12:23

This is one of the 2005 IOCCC winners, a C program that, except by that bunch of defines, looks like a java program:

 * Sun's Java is often touted as being "portable", even though my code won't
 * suddenly become uber-portable if it's in Java. Truth is, Java's one of
 * the most ugly, slow, and straitjacketed languages ever. It's popular
 * mainly because people hear the word "portable" and go "ewww".
 * This program, then, is dedicated to bringing about the death of Java. We
 * good coders have been oppressed for too long by the lame language
 * decisions of pointy-haired bosses and academics who should know better. 
 * It's time we stand up against this junk, and bring back the fun in
 * programming! Viva La Revolution!

#define aSet c
#define BufferedReader(x)1
#define byte Y[I][_^1]?do(:):_&1?do(.):do(`):8;++y;}
#define class int N=0,_,O=328,l=192,y=4,Y[80][64]={0},I;struct
#define do(c)a(#c "\b")
#define err c,c
#define getAllStrings(x));q()
#define if(x)b(#x)
#define IOException
#define line c
#define main(a)b(char*x){write(1,"\033[",2),null}main()
#define new
#define null a(x);}a(char*x){write(1,x,strlen(x));try;try;try;try;
#define out c,c
#define println(x)c
#define private int d(int
#define public short c;}c;typedef int BufferedReader;char*F="JF>:>FB;;BII";
#define return {return
#define static f(x){N=(N+x)%6,y--?f(0),f(1),f(4),f(1):++Y[(I=O+N[F]-66)
#define String
#define System c
#define this if(D):1,O=I,I/=16,l<_/32?if(B):l>_/32?if(A):2,l=_,_/=16,byte
#define throws
#define toArray(x)c
#define try for(;--c.c;)
#define void /16][(_=l+N[6+F]-66)/16]?O/=16,l/=32,O<I/16?if(C):O>I/16?this
#define while(k)if(2J),if(7;21H),f(0),f(4),f(4),if(H),/*

import java.io.*;
import java.util.*;

 * A lame Java program.
 * @author  J. Random Worker
class LameJavaApp

    /** The infamous Long-Winded Signature From Hell. */
    public static void main(String[] args)
        throws IOException
        /* Don't get me started on this. */
        BufferedReader reader =
            new BufferedReader(new FileReader(args[0]));

        /* What, this long incantation just to print a string? */
        System.err.println("Hello world!");

        /* At least this is sane. */
        String line;
        while ((line = reader.readLine()) != null)

     * Method with a needlessly long name.
     * @param   aSet        a set (!)
    private String[] getAllStrings(Set<String> aSet)
         * This dance is needed even in J2SE 5, which has type
         * templates. It was worse before that.
        return aSet.toArray(new String[0]);

  • 3
    \$\begingroup\$ Verbosity at its finest. \$\endgroup\$
    – qwr
    Commented Mar 25, 2014 at 4:48

C++ in C

OK, so you are a C++ programmer, but are forced to use C? No problem, you just have to write some supplementary headers missing in C. For example, here's a valid Hello World program in C:

In the supplementary header file iostream, write:

#include <stdio.h>

#define using volatile int
#define namespace message
#define std = 0
#define message(x) printf("%s\n",x)
#define cout 0
#define endl 0

In file string, write

#define string

In file helloworld.c (your actual C code), write

#include <iostream>
#include <string>

using namespace std;

int main()
  string message("Hello world");
  cout << message << endl;
  return 0;

And when compiling helloworld.c with a C compiler, instruct the compiler to also look for <...> header files wherever you stored the files iostream and string, for example, if you are compiling with gcc and put the files iostream and string in the current directory, compile with

gcc helloworld.c -o helloworld -I.

Note: The volatile in header iostream is there to enable a warning-free compile even at maximum warning level (a read from a volatile variable is considered to have an effect).

  • 3
    \$\begingroup\$ This is a bit of code trolling, isn't it. \$\endgroup\$
    – Mr Lister
    Commented Mar 24, 2014 at 10:15
  • \$\begingroup\$ Well, the program does exactly what it appears to do, doesn't it? \$\endgroup\$
    – celtschk
    Commented Mar 24, 2014 at 10:17
  • 8
    \$\begingroup\$ So much funnier and more impressive this way around than C in C++. \$\endgroup\$ Commented Mar 25, 2014 at 19:56
  • \$\begingroup\$ What kind of compiler warns if you don't use volatile here, and what kind of warning? \$\endgroup\$ Commented Mar 27, 2014 at 9:17
  • 1
    \$\begingroup\$ @KyleStrand But the "C in C++" one is more in tune with the quote in the question. Real programmers program in C, even if they have a C++ compiler. \$\endgroup\$
    – Mr Lister
    Commented Mar 27, 2014 at 11:06

CQL - Caffeinated Query Language

(or "SQL on Caffeine")

This may have been somewhat overly ambitious. Here is an attempt to write SQL(ish) declarative code in CoffeeScript. This requires the ECMAScript 6 Proxy feature. You can test it in node with --harmony-proxies.

Let's set up a template for defining proxies. (Taken from Benvie's comment on this issue)

forward = (->
  _slice  = Array.prototype.slice
  _bind   = Function.prototype.bind
  _apply  = Function.prototype.apply
  _hasOwn = Object.prototype.hasOwnProperty

  Forwarder = (target) ->
    @target = target

  Forwarder.prototype =
    getOwnPropertyNames: -> Object.getOwnPropertyNames(@target)
    keys: -> Object.keys(@target)
    enumerate: ->
      i = 0
      keys = []
      for value of @target
        keys[i++] = value
    getPropertyDescriptor: (key) ->
      o = @target;
      while o
        desc = Object.getOwnPropertyDescriptor o, key
        if desc
          desc.configurable = true;
          return desc;

        o = Object.getPrototypeOf o
    getOwnPropertyDescriptor: (key) ->
      desc = Object.getOwnPropertyDescriptor @target, key
      if desc
        desc.configurable = true
    defineProperty: (key, desc) -> Object.defineProperty @target, key, desc
    get: (receiver, key) -> @target[key]
    set: (receiver, key, value) ->
      @target[key] = value;
    has: (key) -> key of @target
    hasOwn: (key) -> _hasOwn.call @target, key
    delete: (key) ->
      delete @target[key]
    apply: (receiver, args) -> _apply.call @target, receiver, args
    construct: (args) -> new (_bind.apply @target, [null].concat args);

  forward = (target, overrides) ->
    handler = new Forwarder target;
    for k of Object overrides
      handler[k] = overrides[k]

    if typeof target is 'function'
      return Proxy.createFunction handler,
                                  -> handler.apply this, _slice.call arguments,
                                  -> handler.construct _slice.call arguments
      return Proxy.create handler, Object.getPrototypeOf Object target


Now define a proxy object and some suspicious global variables and functions:

sql = forward {
  tables: {}

  finalize: ->
    if typeof @activeRows isnt 'function'
      @result = []
      for row in @activeRows
        @result.push (val for val, i in row when @activeTable.columns[i] in @activeColumns)
    delete @activeRows
    delete @activeColumns
    delete @activeTable

  run: (q) ->
    result = @result
    delete @result
    if typeof result isnt 'function' then console.log result
    return result
}, {
  get: (o,name) ->
    if name of @target
      return @target[name];
    (args...) -> {

int = Number
varchar = (l) -> String

TABLE = (x) -> x
INTO = (x) -> x
CREATE = (tableData) ->
  name = tableData.name
  table =
    columns: []
  column = tableData.args[0]
  table[column.name] = []
  while column = column.args[1]
    table[column.name] = []

  sql.tables[name] = table

  sql.result = "Created table '#{name}'"

INSERT = (table) -> sql.activeTable = sql.tables[table().name]
VALUES = (rows...) ->
  for row in rows
    for val, i in row
      column = sql.activeTable.columns[i]
      sql.activeTable[column].push val

  sql.result = "Inserted #{rows.length} rows"

FROM = (table) ->
  sql.activeTable = sql.tables[table().name]
SELECT = (columns...) ->
  sql.activeColumns = []
  for col in columns
    if typeof col is 'function'
      col = col()

    sql.activeColumns.push col.name

  sql.activeRows = []
  for val in sql.activeTable[sql.activeTable.columns[0]]
    sql.activeRows.push []

  for col in sql.activeTable.columns
    for val, i in sql.activeTable[col]
      sql.activeRows[i].push val

IN = (list) -> { op: 'in', list }
WHERE = (column) ->
  i = sql.activeTable.columns.indexOf(column.name)
  if column.args[0].op is 'in'
    list = column.args[0].list
    sql.activeRows = (row for row in sql.activeRows when row[i] in list)
    console.log 'Not supported!'

ASC = 'asc'
DESC = 'desc'
BY = (x) -> x
ORDER = (column) ->
  i = sql.activeTable.columns.indexOf(column.name)
  order = if column.args[0] is sql.ASC then 1 else -1
  sql.activeRows.sort (a,b) ->
    if a[i] < b[i]
      return -order
    else if a[i] > b[i]
      return order
      return 0

Well that was quite a lot of setup! But now we can do the following (input/output in a console style):

> sql.run ->
    CREATE TABLE @books(
      @title varchar(255),
      @author varchar(255),
      @year int

Create Table 'books'

> sql.run ->
    INSERT INTO @books
    VALUES ['The C++ Programming Language', 'Bjarne Stroustrup', 1985],
           ['Effective C++', 'Scott Meyers', 1992],
           ['Exceptional C++', 'Herb Sutter', 2000],
           ['Effective STL', 'Scott Meyers', 2001];

Inserted 4 rows

> sql.run ->
    SELECT @title, @year FROM @books
    WHERE @author IN ['Bjarne Stroustrup', 'Scott Meyers']
    ORDER BY @year DESC;

[ [ 'Effective STL', 2001 ],
  [ 'Effective C++', 1992 ],
  [ 'The C++ Programming Language', 1985 ] ]

It's not an actual polyglot, but that's not really the point. I know that @ is used for variables in SQL, but I need all the @s for column and table names because I haven't found a way to proxy the global object (and I wouldn't be surprised if it's really not possible - and for a good reason).

I also changed some parentheses into brackets (in particular after VALUES and IN). Unfortunately, what I couldn't figure out at all is a way to allow normal conditionals like year > 2000, because they would evaluate to a boolean right away.

Still this looks a lot like SQL and is definitely more declarative than imperative/functional/object-oriented so it should qualify nicely for the question. I'm actually thinking if I polished the code a bit and supported a few more features, this could be a useful CoffeeScript module.

Anyway, this was fun! :)

For those not too familiar with CoffeeScript, the SQL queries compile to the following JavaScript:

sql.run(function() {
  return CREATE(

sql.run(function() {
  return VALUES([...], ['Effective C++', 'Scott Meyers', 1992], [...], [...]);

sql.run(function() {
  SELECT(this.title, this.year(FROM(this.books)));
  WHERE(this.author(IN(['Bjarne Stroustrup', 'Scott Meyers'])));
  return ORDER(BY(this.year(thisESC)));
  • \$\begingroup\$ That is quite a lot of setup, but does look good. I am not a CoffeeScript programmer, but it does look great. The @ in SQL is used for session variables. \$\endgroup\$ Commented Mar 21, 2014 at 14:34
  • \$\begingroup\$ I decided to make the keywords global now. Now there are only @s for column and table names. \$\endgroup\$ Commented Mar 21, 2014 at 15:50
  • \$\begingroup\$ Now it looks a lot like SQL! You did a nice work with this one! \$\endgroup\$ Commented Mar 21, 2014 at 16:06
  • 1
    \$\begingroup\$ I don’t care much for coffee, but this is awesome. \$\endgroup\$
    – KRyan
    Commented Mar 28, 2014 at 4:46
  • 2
    \$\begingroup\$ @tac thanks, but no I just hacked it together for this challenge. Funny coincidence: redoing this in a clean way and putting it on GitHub was on my list of potential/long-term coding projects until I removed it just this morning. \$\endgroup\$ Commented Mar 21, 2016 at 16:40

Visual Basic 6 (in JavaScript)

'; Main sub-routine \
'; function Main() { ' \
Sub Main() '
    ' Do not throw any errors... \
    On Error Resume Next '; MsgBox = alert

    ' Show a message box... \
    MsgBox(1 / 0) '

    ' Show errors again... \
    On Error GoTo 0 '

    ' Show another message box... '
    ' ' } ' \
End Sub '


It also works in VBScript.

  • 1
    \$\begingroup\$ Clever. You don't even need most of the semicolons. \$\endgroup\$
    – js1568
    Commented Mar 21, 2014 at 20:42
  • \$\begingroup\$ @js1568 Thank you! I've now removed the semi-colons that aren't needed. \$\endgroup\$
    – Toothbrush
    Commented Mar 24, 2014 at 14:07

F# in C++

Rather unimaginative and nasty abuse of the preprocessor. I thought it'd be fun to alter C++ to look like a completely dissimilar language instead of using a few aliases to make it look like Java or PHP. I'm not really expecting this to garner a ton of upvotes, it's a just-for-fun entry.

#define let int
#define args ( int __, char* args[] ) { int ___ 
#define println printf(
#define exit "\n" ); return 0; }
#include <stdio.h>

let main args =
    println "F# is better than C++"

Try it here.

Sadly writing something to STDOUT is about all it can do, although I'm sure if someone threw enough witchcraft at it they could make it do more.

  • 2
    \$\begingroup\$ For the last line to work in F#, it would either have to be exit 0 or just 0. \$\endgroup\$
    – Jwosty
    Commented Mar 27, 2014 at 3:44

Python and... nobody will guess (edit: dc)

Here is some valid python code, but actually the program is written in a very different language:

# Initialize systems 1 and 2
# frame 1, divergency speed and divergency latency
f1ds, f1dl, z1 = [2,2,0]
# frame 2, divergency speed and divergency latency
f2ds, f2dl, z2 = [4,4,1]

# Set the most relevant value of ax (detected by low-energy collision)
ax = 42.424242

# Initialize list of successive energy states
s = [17.98167, 21.1621, 34.1217218, 57.917182]

# Most common value for nz parameter
# TODO: check if value from the article of A. Einstein is better
nz = 10

if z2>nz or ax in s:
  ax += 6
  f1ds = 8
  f2ds = 16
  z1 = 4
  z2 = 9

f1dl += z1
f2dl += z2

# main loop, iterate over all energy states
# Warning: hit Ctrl-C if nuclear explosion occurs and adjust either z or nz
for k in s:
  z = nz + k
  f1dl = f1ds + f2dl * z - z1 + 3.14
  f2dl = f2ds + f1dl * z - z2 + 10
  if k > 10 or z-2 in s:
    nz += 0xac  # hexadecimal coefficient found in famous article by E. Fermi

The code runs in both languages with no error.

The combination is very crazy; I would be happy to wait one day or two before telling which is the other language; please leave comments for guessing.

edit: The language was the stack-based language from dc. You may see here well-known keywords like for, if, or, in, but only the letters matter! The , which has no meaning in dc is turned to a register because the first time it appears is after the letter s (the same for :).

  • 1
    \$\begingroup\$ Unless the code does the same thing in both languages, I suppose a language like Befunge could do the trick. \$\endgroup\$ Commented Mar 22, 2014 at 0:25
  • \$\begingroup\$ OK, I edit the code in order to put the language I actually chose. \$\endgroup\$ Commented Mar 22, 2014 at 4:38

C++ allows you to write lisp-like code, with the InteLib library:

     (L|(L|ATOM, TREE1), (L|ATOM, TREE2)),
     (L|(L|ATOM, TREE2), NIL),
     (L|T, (L|AND,
       (L|ISOMORPHIC, (L|CAR, TREE1), 
                      (L|CAR, TREE2)),
       (L|ISOMORPHIC, (L|CDR, TREE1), 
                      (L|CDR, TREE2))

cf. http://www.informatimago.com/articles/life-saver.html

  • 4
    \$\begingroup\$ Welcome! We ask users to flag their posts as Community Wiki when the answer is not their own work. (And give proper attribution, but you already did that, so thank you!) \$\endgroup\$ Commented Mar 23, 2014 at 11:47
  • \$\begingroup\$ Original or not, you got my vote :) \$\endgroup\$
    – itsjeyd
    Commented Mar 25, 2014 at 22:56

C# in Whitespace

Okay, first try at one of these, so let's see how it goes.

using System; //very important  

namespace ConsoleApplication1  //namespace: name whatever you want      
 class  Program  //class name:  also anything    
    //main function 
    static void Main(string[] args) {
        for(int i=0;i<10;i++)   writeOutput(i); 
    } //end main    
    static void writeOutput(int i) { Console.WriteLine(i); }    //display output    

    } //class ends here         

}  //close namespace:   also very important     


And in case the formatting went screwy from having to put four spaces at the front of each line, here it is again with . for space and # for tab:







Not programming languages, but … this document is valid HTML and CSS:

<!-- p{color:red} /* -->
<!Doctype html>
<title>This is HTML and CSS</title>
<!-- */ -->
<!-- p{color:red} /* -->
<!Doctype html>
<title>This is HTML and CSS</title>
<!-- */ -->

This works, because HTML comments are allowed in stylesheets for historical reasons. Oh, and every valid HTML document is a valid PHP program too, so this is also PHP. :)


C in Scala

The bridging layer emulates a more romantic era when strings were still null terminated arrays of bytes.

// Scala is a dynamic language
import scala.language.{ dynamics, postfixOps }

val self = this

val argc = args.length
val argv = args.map(_.getBytes)

type char = Array[Byte]
object char extends Dynamic {
  // This program uses expanded memory
  val buffers = new scala.collection.mutable.LinkedHashMap[String, char]

  // Malloc char buffer
  def applyDynamic(name: String)(length: Int) =
    buffers(name) = new Array(length)

  def **(argv: Array[Array[Byte]]) = argv

object & extends Dynamic {
  // dereference char pointer
  def selectDynamic(name: String) = char.buffers(name)

def printf(format: String, buffers: char*) =
    (format /: buffers){ case (msg, buffer) =>
      // Read string until \0 terminator
      val value = new String(buffer.takeWhile(0 !=))
      // Replace next %s token
      msg.replaceFirst("%s", value)

def scanf(format: String, buffers: char*) =
  buffers foreach { buffer =>
    val line = Console.readLine()
    // Write string to char* buffer
    line.getBytes(0, line.length, buffer, 0)
    // Remember to always null terminate your strings!
    buffer(line.length) = 0

val PATH_MAX = 4096

implicit class Argumenter(args: Pair[_, _]) {
  def apply[T](f: => T) = f

object int {
  // Passthrough
  def main[T](f: => T) = f
  def argc = self.argc

// terminates the string after the first character
// investigate switching to "xor eax, eax" instead of having a hardcoded 0
// might save 3 bytes and valuable CPU time with this trick
val initialize = (_: char)(1) = 0

def exit(value: Int) = sys.exit(value)

int main(int argc, char **argv) {
  if (argc != 0) {
    printf("This program does not take parameters!");

  // I've copy pasted this code from somewhere
  // Code reuse is essential if we want to be DRY
  char first(PATH_MAX + 1);
  char last(PATH_MAX + 1);

  printf("Enter your first and last name:\n");
  scanf("%s%s", &first, &last);

  // Still learning references, do I need these here?
  // I've performed benchmarks on printf and I think it's faster this way
  printf("Your full name is %s %s", &first, &last);

  printf("Your signature is %s. %s", &first, &last);

  • \$\begingroup\$ "This program does not take parameters!" fooled ya \$\endgroup\$ Commented Sep 6, 2016 at 15:03

sed and APL

My boss wants me to write sed scripts, but I like rather writing APL all the day. Nevertheless, he is very happy with my job because such scripts run perfectly with his version of sed:

i ← g ← 42
a ← d ← 10

You can try it on my new website with this permalink. It is a compiled to javascript version of GNU APL. Final release will be later with official release of GNU APL, v. 1.3 but you can perfectly use it for your permalinks if you enjoy GNU APL.


C in Haskell

import Foreign.C.String
import Foreign.C.Types
import Foreign.Marshal.Array
import Foreign.Ptr
import System.Environment
import System.Exit

-- The meat of the program

cmain :: (CInt, Ptr (Ptr CChar)) -> IO CInt
cmain(argc, argv) = do {
    putStr("hello, world\n");
    return 0;

-- Of course, the above function doesn't do anything unless we write a wrapper
-- around it.  This could have been done more simply, using higher-level library
-- functions, but where's the fun in that?

main :: IO ()
main = do {
    args <- getArgs;
    argPtrs <- sequence [do {
        argPtr <- mallocArray0(length(arg)) :: IO (Ptr CChar);
        return argPtr;
    } | arg <- args ];
    argv <- mallocArray(length(argPtrs)) :: IO (Ptr (Ptr CChar));

    exitCode <- cmain(fromIntegral(length(args)),argv);

    if (exitCode == 0) then do {
    } else do {

Of course, since cmain doesn't do anything with argc or argv, the argument-marshaling code has no effect, and since cmain always returns 0, the "else" branch of the "if" statement is dead. But the "if" statement doesn't do anything anyway.

All of the braces and semicolons are unnecessary, as are most of the parentheses and some of the do keywords. The "if" statement could have been written as if exitCode == 0 then exitWith ExitSuccess else exitWith (ExitFailure (fromIntegral exitCode)).


C++ in Forth

: #include ; : <iostream> ; : { ; : } ; : int ; : using ;
: namespace ; : std; ; : main() ; : cout ; : << ;
: "Hello,  ; : world!\n"; S" Hello, world!" type ; : return ; : 0; ;

#include <iostream>
using namespace std;

int main() {
    cout << "Hello, world!\n";

Not the most flexible solution, but it works if written exactly as shown.


Haskell in Java

("vanilla" Java 7, not Java 8) (Yes, I know that boxing ruins performance; and even trying to use higher order functions gets crazy verbose :D)

Java has very rigid syntax, so instead of changing syntax I tried to make code semantically more similar to Haskell style.

Edit — added partial function application.

import java.util.Iterator;

interface Function1<A, B> {
    A call(B arg);

interface Function2<A, B, C> {
    A call(B arg1, C arg2);

class Reduce<A> implements Function2<A, Function2<A, A, A>, Iterable<A>> {

    public A call(Function2<A, A, A> arg1, Iterable<A> arg2) {
        final Iterator<A> i = arg2.iterator();
        A r = i.next();
        while (i.hasNext())
            r = arg1.call(r, i.next());
        return r;

class Range implements Iterable<Integer> {

    private final int min;
    private final int max;

    public Range(int min, int max) {
        this.min = min;
        this.max = max;

    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {
            int i = min;

            public boolean hasNext() {
                return i <= max;

            public Integer next() {
                return i++;

            public void remove() {
                throw new UnsupportedOperationException();

public class Main {

    public static <A, B, C> Function1<A, C> applyPartial(final Function2<A, B, C> f, final B arg2) {
        return new Function1<A, C>() {
            public A call(C arg) {
                return f.call(arg2, arg);

    public static void main(String[] args) {

        final Function1<Integer, Iterable<Integer>> product = applyPartial(new Reduce<Integer>(), new Function2<Integer, Integer, Integer>() {
            public Integer call(Integer arg1, Integer arg2) {
                return arg1 * arg2;

        final Function1<Integer, Integer> fact = new Function1<Integer, Integer>() {

            public Integer call(Integer arg) {
                return product.call(new Range(1, arg));

        final Integer x = fact.call(6);


(Yes, all that this madness does is computing 6!)



In the spirit of the quote. Pure, unadulterated AWK, as it may be written by a COBOL programmer.

The task is to count the records on a file. This early development version is counting itself for testing. The correct file will be hard-coded later when released from Unit Testing...

If I could get the syntax highlighting to do phosphorescent-green on black, it would be great...

Even got the column-numbers correct on this one, that's seven blanks at the start of each line (never done that in awk before) and breaking the long print statements at column 72.

   BEGIN { 
   function PERFORM_000_INITIALISATION() { 
       RECORD_COUNT = 0 
   function PERFORM_100_OPEN_FILES() { 
   function PERFORM_200_PROCESS_FILE() { 
   function PERFORM_300_CLOSE_FILES() { 
   function PERFORM_400_SHOW_THE_COUNTS() { 
   function PERFORM_210_PRIMING_READ() { 
       if ( FILE_STATUS < 0 ) { 
           print "COBOL.AWK ERR0001: INVALID FILE, HALTING, FILE N" \
                 "AME IS: " INPUT_FILE_NAME 
       if ( FILE_STATUS == 0 ) { 
           print "COBOL.AWK ERR0002: NO RECORDS ON INPUT, HALTING," \
                 "FILE NAME IS: " INPUT_FILE_NAME 
       while ( FILE_STATUS != 0 ) { 
           INPUT_RECORD = $0 
   function PERFORM_900_READ_THE_FILE() { 
       FILE_STATUS = getline < INPUT_FILE_NAME 

SML in Java

I still have some ancient code around from when I started learning Java and tried to use it in a functional style. Slightly cleaned up:

 * Genericised ML-style list.
public class FunctionalList<T> 
    private final T head;
    private final FunctionalList<T> tail;

    public FunctionalList(T x, FunctionalList<T> xs) {
        this.head = x;
        this.tail = xs;

    public static <T> FunctionalList<T> cons(T x, FunctionalList<T> xs) {
        return new FunctionalList<T>(x, xs);

    public static <T> T hd(FunctionalList<T> l) {
        return l.head;

    public static <T> FunctionalList<T> tl(FunctionalList<T> l) {
        return l.tail;

    public static int length(FunctionalList<?> l) {
        return len(l, 0);

    private static int len(FunctionalList<?> l, int n) {
        return l == null ? n : len(tl(l), n + 1);

    public static <T> FunctionalList<T> rev(FunctionalList<T> l) {
        return rev(l, null);

    private static <T> FunctionalList<T> rev(FunctionalList<T> a, FunctionalList<T> b) {
        return a == null ? b : rev(tl(a), cons(hd(a), b));

    public static <T> FunctionalList<T> append(FunctionalList<T> a, FunctionalList<T> b) {
        return a == null ? b : cons(hd(a), append(tl(a), b));

Java in Perl

May count as rule breaking, but I don't care. Obviously, it's intended to look like Java program. It prints 20 Fibonacci numbers, in case it isn't obvious.

Requires Inline::Java module to be installed.

use Inline Java => <<'JAVA';
 * @author  Konrad Borowski <[email protected]>
 * @version 0.1.0
class Fibonacci
     * Responsible for storing the number before last generated number.
    private long beforeLastNumber = 0;

     * Responsible for storing the last generated number.
    private long lastNumber = 1;

     * Receives the next Fibonacci number.
     * @return long integer that is the next Fibonacci number
    public long next()
        long temponaryLastNumber = lastNumber;
        lastNumber = beforeLastNumber + lastNumber;
        beforeLastNumber = temponaryLastNumber;
        return temponaryLastNumber;

     * Outputs the Fibonacci number to standard output.
    public void printFibonacci()

     * Outputs the Fibonacci number to standard output given number of
     * times.
     * @param times number of times to print fibonacci number
    public void printFibonacciTimes(int times)
        int i;
        for (i = 0; i < times; i++) {

     * Constructor for Fibonacci object. Does nothing.
    public Fibonacci()
        // Do nothing.

 # The executable class that shows 20 Fibonacci numbers.
package OutputFibonacci
     # Shows 20 Fibonacci numbers. This method is public,
     # static, and returns void.
    sub main()
        # In Perl, -> is object method separator, not a dot. This is stupid.
        new Fibonacci()->printFibonacciTimes(20);

# Perl doesn't automatically call main method.

Brainfuck (or anything else) in Racket

Racket's flexible module and macro system allows it to implement module support for entirely new languages, both domain-specific and general-purpose. There is out of the box support for both Datalog and Algol 60, so the following are both valid Racket programs:

#lang datalog
edge(a, b). edge(b, c). edge(c, d). edge(d, a).
path(X, Y) :- edge(X, Y).
path(X, Y) :- edge(X, Z), path(Z, Y).
path(X, Y)?

#lang algol60
  integer procedure SIGMA(x, i, n);
    value n;
    integer x, i, n;
    integer sum;
    sum := 0;
    for i := 1 step 1 until n do
      sum := sum + x;
    SIGMA := sum;
  integer q;
  printnln(SIGMA(q*2-1, q, 7));

You can also add support for other languages: e.g. see Danny Yoo's description of how to implement support for Brainfuck, which permits Racket programs such as:

#lang planet dyoo/bf

And since the support is added at the compiled module level, it's possible to link modules written in different languages or embed a snippet of one language inside a module written in another.


J and... nobody will guess (edit: dc)

This is my second entry; here is a piece of valid J code, which returns 1:

10 o. 1 r. 2 i. 4 [ ( 0:`1: @. (2&|)) ] 8 #: *:@+: 42

I am waiting one or two day before telling which is the other language running the very same piece of code with no error. Just leave comments for trying to guess.

edit: The other language is the stack-based language from the very ancient Unix calculator dc.

  • 3
    \$\begingroup\$ It runs without errors in GolfScript, BF, HQ9+, ... \$\endgroup\$ Commented Mar 21, 2014 at 22:38
  • \$\begingroup\$ OK, I wasn't aware that such many languages could do it. I edit the code in order to put the language I actually chose. \$\endgroup\$ Commented Mar 22, 2014 at 4:37
  • \$\begingroup\$ @ברוכאל it runs without errors in those languages because those languages don't have errors, or don't have errors applicable to this code. Eg. Brainfuck ignores all characters that are not in .,+-<>[] so your program is equivalent to ...[.]+ in brainfuck which is a valid but pointless program. AFAIK a brainfuck program can only be invalid by having mismatched []. \$\endgroup\$ Commented Mar 27, 2014 at 1:12
  • \$\begingroup\$ @immibis. This is false. dc is an old calculator and I can assure that changing one thing in my codes would raise an error. I spent much time on some parts of the code to figure out some tricky way of putting the letters in the right order. My piece of code Postscript/dc is quite extreme: no error but changing anything will make it faulty. dc has nothing to do with "those languages"; dc is about 20 or 30 years older than "those languages"; it is generally installed on any Linux distribution. Please, browse a little if you haven't heard about it. \$\endgroup\$ Commented Mar 27, 2014 at 3:57
  • 1
    \$\begingroup\$ @ברוכאל you misunderstood - I was talking about brainfuck, HQ9+, golfscript, etc. - not dc. \$\endgroup\$ Commented Mar 27, 2014 at 4:50

dc running a PostScript file

dc can run the following piece of code with no error:

10 10 10 10 10 42 32 10 10
stop % first send a stop
0 0 srand rand
le pop pop 3.14 sin
lt 2 3 lt and pop
le 2 10 le xor
pop pop pop 1 0 0
<< /sox 2 >> [ exch begin sox end ] aload
3.14 floor

ML/(Strict) Haskell in Java

This is from an actual real project. It makes use of persistent immutable data structures and uses recursion even when not necessary. Actually, it's more like Kore (the language the project implements) in Java, but the style is basically the same as ML. But the philosophy of Kore is that the author shouldn't format his code, so none of the Java code is formatted either (it's autoformatted by eclipse).

drop n elements from a list:

  public static <T> List<T> drop(List<T> l, Integer n) {
    return n == 0 ? l : drop(l.cons().tail, n - 1);

In ML/Haskell, where you'd pattern match to extract the head and tail, here you say list.cons().x and list.cons().tail.

insert an element in a list:

  public static <T> List<T> insert(List<T> l, Integer i, T x) {
    if (i == 0)
      return cons(x, l);
    return cons(l.cons().x, insert(l.cons().tail, i - 1, x));

List is defined literally how the algebraic datatype would be defined. Here is a version with the eclipse-generated boilerplate removed:

public final class List<T> {

  public static final class Nil<T> {

  public static final class Cons<T> {
    public final T x;
    public final List<T> tail;

    public Cons(T x, List<T> tail) {
      if (x == null)
        throw new RuntimeException("null head");
      if (tail == null)
        throw new RuntimeException("null tail");
      this.x = x;
      this.tail = tail;

  private final Nil<T> nil;
  private final Cons<T> cons;

  private List(Nil<T> nil, Cons<T> cons) {
    this.nil = nil;
    this.cons = cons;

  public boolean isEmpty() {
    return nil != null;

  public Nil<T> nil() {
    if (nil == null)
      throw new RuntimeException("not nil");
    return nil;

  public Cons<T> cons() {
    if (cons == null)
      throw new RuntimeException("not cons");
    return cons;

  public static <T> List<T> cons(Cons<T> cons) {
    if (cons == null)
      throw new RuntimeException("constructor received null");
    return new List<T>(null, cons);

  public static <T> List<T> nil(Nil<T> nil) {
    if (nil == null)
      throw new RuntimeException("constructor received null");
    return new List<T>(nil, null);

Here is a map data structure implemented in terms of a trie:

public final class Map<K, V> {
  private final Tree<Character, Optional<Pair<K, V>>> tree;
  // keys are sorted in reverse order so entrySet can use cons instead of append
  private final Comparer<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> comparer =
      new PairLeftComparer<Character, Tree<Character, Optional<Pair<K, V>>>>(
          new ReverseComparer<Character>(new CharacterComparer()));

  private Map(Tree<Character, Optional<Pair<K, V>>> tree) {
    this.tree = tree;

  public static <K, V> Map<K, V> empty() {
    return new Map<K, V>(new Tree<Character, Optional<Pair<K, V>>>(
        OptionalUtils.<Pair<K, V>> nothing(),
            .<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> nil()));

  public Optional<V> get(K k) {
    Tree<Character, Optional<Pair<K, V>>> t = tree;
    for (char c : k.toString().toCharArray()) {
      Tree<Character, Optional<Pair<K, V>>> t2 = getEdge(t, c);
      if (t2 == null)
        return nothing();
      t = t2;
    if (t.v.isNothing())
      return nothing();
    return some(t.v.some().x.y);

  public Map<K, V> put(K k, V v) {
    return new Map<K, V>(put(tree, k.toString(), v, k));

  private Tree<Character, Optional<Pair<K, V>>> put(
      Tree<Character, Optional<Pair<K, V>>> t, String s, V v, K k) {
    if (s.equals(""))
      return new Tree<Character, Optional<Pair<K, V>>>(some(Pair.pair(k, v)),
    char c = s.charAt(0);
    Tree<Character, Optional<Pair<K, V>>> t2 = getEdge(t, c);
    if (t2 == null)
      return new Tree<Character, Optional<Pair<K, V>>>(
                      put(new Tree<Character, Optional<Pair<K, V>>>(
                          OptionalUtils.<Pair<K, V>> nothing(),
                              .<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> nil()),
                          s.substring(1), v, k)), t.edges), comparer));
    return new Tree<Character, Optional<Pair<K, V>>>(t.v, sort(
        replace(pair(c, put(t2, s.substring(1), v, k)), t.edges), comparer));

  private List<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> replace(
      Pair<Character, Tree<Character, Optional<Pair<K, V>>>> edge,
      List<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> edges) {
    if (edges.cons().x.x.equals(edge.x))
      return cons(edge, edges.cons().tail);
    return cons(edges.cons().x, replace(edge, edges.cons().tail));

  // I consider this O(1). There are a constant of 2^16 values of
  // char. Either way it's unusual to have a large amount of
  // edges since only ASCII chars are typically used.
  private Tree<Character, Optional<Pair<K, V>>> getEdge(
      Tree<Character, Optional<Pair<K, V>>> t, char c) {
    for (Pair<Character, Tree<Character, Optional<Pair<K, V>>>> p : iter(t.edges))
      if (p.x.equals(c))
        return p.y;
    return null;

  public Map<K, V> delete(K k) {
    return new Map<K, V>(delete(tree, k.toString()).x);

  private Pair<Tree<Character, Optional<Pair<K, V>>>, Boolean> delete(
      Tree<Character, Optional<Pair<K, V>>> t, String k) {
    if (k.equals(""))
      return pair(
          new Tree<Character, Optional<Pair<K, V>>>(
              OptionalUtils.<Pair<K, V>> nothing(), t.edges), t.edges.isEmpty());
    char c = k.charAt(0);
    Tree<Character, Optional<Pair<K, V>>> t2 = getEdge(t, c);
    if (t2 == null)
      return pair(t, false);
    Pair<Tree<Character, Optional<Pair<K, V>>>, Boolean> p =
        delete(t2, k.substring(1));
    List<Pair<Character, Tree<Character, Optional<Pair<K, V>>>>> edges = nil();
    for (Pair<Character, Tree<Character, Optional<Pair<K, V>>>> e : iter(t.edges))
      if (!e.x.equals(c))
        edges = cons(e, edges);
    if (!p.y)
      return pair(
          new Tree<Character, Optional<Pair<K, V>>>(t.v, cons(pair(c, p.x),
              edges)), false);
    boolean oneEdge = t.edges.cons().tail.isEmpty();
    return pair(new Tree<Character, Optional<Pair<K, V>>>(t.v, edges), oneEdge
        && t.v.isNothing());


  public static class Entry<K, V> {
    public Entry(K k, V v) {
      this.k = k;
      this.v = v;

    public final K k;
    public final V v;


  public List<Entry<K, V>> entrySet() {
    return entrySet(ListUtils.<Entry<K, V>> nil(), tree);

  private List<Entry<K, V>> entrySet(List<Entry<K, V>> l,
      Tree<Character, Optional<Pair<K, V>>> t) {
    if (!t.v.isNothing()) {
      Pair<K, V> p = t.v.some().x;
      l = cons(new Entry<K, V>(p.x, p.y), l);
    for (Pair<Character, Tree<Character, Optional<Pair<K, V>>>> e : iter(t.edges))
      l = entrySet(l, e.y);
    return l;

The types start to take up as much space as the code. For example, in put, the method has 302 characters of types and 343 characters of code (not counting space/newlines).


BASIC in Ruby

Implemented this long ago. The source is on GitHub. Inspired by a similar thing in Scala


#!/usr/bin/env ruby

if caller.empty? && ARGV.length > 0
  $file = ARGV[0]
  $file = caller.last.split(':').first

require 'pp'

class String
  def %(other)
    self + other.to_s

class RBaysick
  @@variables = {}
  @@code = []
  @@line = 0

  def initialize(contents)
    $DONT_RUN = true # To avoid endless loops.

    contents.gsub!(/( |\()'([^\W]+)/, '\1:\2 ')

    contents.gsub!(/(^| |\()(:[^\W]+)/, '\1GET(\2)')

    contents.gsub!(/ IF (.*) THEN (.*)/, ' IF { \1 }.THEN { GOTO \2 }')
    contents.gsub!(/LET *\(([^ ]+) *:= *(.*)\)/, 'LET(\1) { \2 }')
    contents.gsub!(/(LET|INPUT)(\(| )GET\(/, '\1\2(')
    contents.gsub!(/ \(/, '(')

    contents.gsub!(/^(\d+) (.*)$/, 'line(\1) { \2 }')

#    contents.gsub!(/(\)|\}|[A-Z]) ([A-Z]+)/, '\1.\2')

    contents.gsub!(/ END /, ' __END ')
    contents.gsub!(/^RUN/, '__RUN')

    puts contents if $DEBUG
    eval contents

  def __RUN
    while @@line > -1
      puts "#{@@line}: #{@@code[@@line].inspect}" if $DEBUG
      unless @@code[@@line].nil?
        @@increment = true
        next unless @@increment
      @@line += 1

  class If < Struct.new(:value)
    def THEN
      yield if value

  def method_missing(name, *args)
    puts "Missing: #{name.to_s}(#{args.map(&:inspect).join(', ')})" if $DEBUG

  def variables

  def line(line, &block)
    @@code[line] = block

  def add(line, cmd, *args)
    puts "DEBUG2: #{cmd.to_s}(#{args.map(&:inspect).join(', ')})" if $DEBUG
    @@code[line] = send(cmd, *args)

  def IF

  def PRINT(str)
    puts "PRINT(#{str.inspect})" if $DEBUG
    puts str

  def LET(name, &block)
    puts "LET(#{name.inspect}, #{block.inspect})" if $DEBUG
    @@variables[name] = block.call

  def GET(name)
    puts "GET(#{name.inspect}) #=> #{@@variables[name].inspect}" if $DEBUG

  def INPUT(name)
    puts "INPUT(#{name.inspect})" if $DEBUG
    LET(name) { $stdin.gets.chomp.to_i }

  def ABS(val)
    puts "ABS(#{val.inspect}) #=> #{val.abs.inspect}" if $DEBUG

  def GOTO(line)
    @@increment = false
    @@line = line

  def __END

RBaysick.new(open($file).read) unless $DONT_RUN || ($0 != __FILE__)

BASIC code


10 PRINT "Welcome to Baysick Lunar Lander v0.0.1"
20 LET ('dist := 100)
30 LET ('v := 1)
40 LET ('fuel := 1000)
50 LET ('mass := 1000)

60 PRINT "You are a in control of a lunar lander."
70 PRINT "You are drifting towards the surface of the moon."
80 PRINT "Each turn you must decide how much fuel to burn."
90 PRINT "To accelerate enter a positive number, to decelerate a negative"

100 PRINT "Distance " % 'dist % "km, " % "Velocity " % 'v % "km/s, " % "Fuel " % 'fuel
110 INPUT 'burn
120 IF ABS('burn) <= 'fuel THEN 150
130 PRINT "You don't have that much fuel"
140 GOTO 100
150 LET ('v := 'v + 'burn * 10 / ('fuel + 'mass))
160 LET ('fuel := 'fuel - ABS('burn))
170 LET ('dist := 'dist - 'v)
180 IF 'dist > 0 THEN 100
190 PRINT "You have hit the surface"
200 IF 'v < 3 THEN 240
210 PRINT "Hit surface too fast (" % 'v % ")km/s"
220 PRINT "You Crashed!"
230 GOTO 250
240 PRINT "Well done"

250 END


Haskell in C++ templates

I made this FizzBuzz in C++ templates a few months ago on a lark. It is pretty much an implementation of the following Haskell code, all in C++ templates. In fact, even the integer arithmetic is reimplemented at the type level --- notice that none of the templates use int parameters!

The Haskell code:

import Control.Monad

m `divides` n = (n `mod` m == 0)

toFizzBuzz n
    | 15 `divides` n = "FizzBuzz"
    |  5 `divides` n = "Buzz"
    |  3 `divides` n = "Fizz"
    |      otherwise = show n

main = mapM_ putStrLn $ take 100 $ map toFizzBuzz [1..]

and the C++ template metaprogramming version:

//  Lazy compile-time fizzbuzz computed by C++ templates,
//  without conditionals or the use of machine arithmetic.
//         -- Matt Noonan ([email protected])

#include <iostream>

using namespace std;

//  The natural numbers: Nat = Zero | Succ Nat

template <typename n>
struct Succ
  typedef Succ eval;
  static const unsigned int toInt = 1 + n::toInt;
  static void print(ostream & o) { o << toInt; }

struct Zero
  typedef Zero eval;
  static const unsigned int toInt = 0;
  static void print(ostream & o) { o << toInt; }

//  Arithmetic operators
//    Plus Zero n = n
//    Plus Succ(n) m = Plus n Succ(m)
//    Times Zero n = Zero
//    Times Succ(n) m = Plus m (Times n m)

template <typename a, typename b>
struct Plus
  typedef typename Plus<typename a::eval,
                        typename b::eval>::eval eval;

template <typename M>
struct Plus <Zero, M>
{ typedef typename M::eval eval; };

template <typename N, typename M>
struct Plus <Succ<N>, M>
{ typedef typename Plus<N, Succ<M> >::eval eval; };

template <typename a, typename b>
struct Times
  typedef typename Times<typename a::eval,
                         typename b::eval>::eval eval;

template <typename M>
struct Times <Zero, M>
{ typedef Zero::eval eval; };

template <typename N, typename M>
struct Times <Succ<N>, M>
{ typedef typename Plus<M,
                        typename Times<N,M>::eval
                        >::eval eval; };

//  Lists

struct Nil
  typedef Nil eval;
  static void print(ostream & o) { }

template <typename x, typename xs>
struct Cons
  typedef Cons eval;
  static void print(ostream & o) {
    x::eval::print(o); o << endl; xs::eval::print(o);

//  Take the first n elements of a list

template <typename, typename> struct Take;

template <typename _> struct Take<Zero,_>
{ typedef Nil eval; };

template <typename n, typename x, typename xs>
struct Take<Succ<n>, Cons<x,xs> >
  typedef Cons<x, Take<n, xs> > eval;

template <typename a, typename b>
struct Take
  typedef typename Take<typename a::eval,
                        typename b::eval>::eval eval;

//  Iterate f x0 makes the infinite list
//  x0, f(x0), f(f(x0)), ...

template <template<typename> class f, typename x0> struct Iterate
  typedef Cons<x0, Iterate<f, f<x0> > > eval;

//  Map a function over a list

template <template<typename> class a, typename b> struct Map
{ typedef typename Map<a,
                       typename b::eval>::eval eval;

template <template<typename> class f>
struct Map<f, Nil>
{ typedef Nil eval; };

template <template<typename> class f, typename x, typename xs>
struct Map<f, Cons<x,xs> >
  typedef Cons<f<x>, Map<f,xs> > eval;

//  Some useful things for making fizzes and buzzes

struct Fizz
{ static void print(ostream & o) { o << "Fizz"; } };

struct Buzz
{ static void print(ostream & o) { o << "Buzz"; } };

struct FizzBuzz
{ static void print(ostream & o) { o << "FizzBuzz"; } };

//  Some useful numbers

typedef Succ<Zero> One;
typedef Succ<One> Two;
typedef Succ<Two> Three;
typedef Plus<Two, Three> Five;
typedef Times<Two, Five> Ten;
typedef Times<Three, Five> Fifteen;
typedef Times<Ten, Ten> OneHundred;

//  Booleans

struct True {};
struct False {};

//  If/then/else

template <typename p, typename t, typename f>
struct If
  typedef typename If<typename p::eval, t, f>::eval eval;
  static void print(ostream & o) { eval::print(o); }

template <typename t, typename _>
struct If<True, t, _>
  typedef t eval;

template <typename _, typename f>
struct If<False, _, f>
{ typedef f eval; };

//  Testing if x divides y

template <typename a, typename b, typename c>
struct _Divides
  typedef typename _Divides<typename a::eval,
                            typename b::eval,
                            typename c::eval>::eval eval;

template <typename _, typename __>
struct _Divides<_, __, Zero> { typedef False eval; };

template <typename a>
struct _Divides<a, Zero, Zero> { typedef True eval; };

template <typename a, typename b>
struct _Divides<a, Zero, b>
  typedef typename _Divides<a, a, b>::eval eval;

template <typename _, typename n, typename m>
struct _Divides<_, Succ<n>, Succ<m> >
  typedef typename _Divides<_, n, m>::eval eval;

template <typename a, typename b>
struct Divides
  typedef typename _Divides<a, a, b>::eval eval;

//  "Otherwise" sugar

template <typename a>
struct Otherwise
  typedef typename a::eval eval;
  static void print(ostream & o) { a::eval::print(o); }

//  Convert a number to fizzes, buzzes as appropriate

template <typename n>
struct toFizzBuzz
  typedef typename
    If< Divides<Fifteen, n>, FizzBuzz,
    If< Divides<   Five, n>,     Buzz,
    If< Divides<  Three, n>,     Fizz,
    Otherwise<                   n
    > > > >::eval eval;

int main(void)
  // Make all of the natural numbers
  typedef Iterate<Succ, One> Naturals;

  // Apply fizzbuzz rules to every natural number
  typedef Map<toFizzBuzz, Naturals> FizzBuzzedNaturals;

  // Print out the first hundred fizzbuzzed numbers
  Take<OneHundred, FizzBuzzedNaturals>::eval::print(cout);

  return 0;

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