Restricted Polyglot

Question

Polyglots are programs that are valid in multiple programming languages simultaneously. Most such polyglots are written in such a way that certain constructs of one language are interpreted as comments of another language (e.g. #define in C being interpreted as a comment in several scripting languages).

I am curious to see if it is possible to make a non-trivial polyglot which contains no comments, but also immediately changes when you remove any non-whitespace character, I therefore challenge you to come up with such a program.

The concrete rules are as follows:

1. (Output). Your program must produce some output on the console under each of your languages. That is, your program is not permitted to simply exit without printing anything.
2. (Variance). As a relaxation of the standard polyglot definition, the program's output may vary between languages.
3. (Errors). Your program must not produce any errors (broadly defined) under any of your languages. For most languages, this is defined as returning a non-zero exit code from the compiler and/or interpreter.
4. (Restriction). The removal of any single non-whitespace character from your code should cause your program to change its behaviour under every one of your languages. The program may "change" by becoming invalid for that language, or by changing the output that is produced.
5. This is a code challenge. Winner is the program which is valid in the most programming languages. Ties will be broken in favor of shorter program length.

The restriction rule doesn't apply to the removal of several characters. That is, it is fine if removing several characters simultaneously results in no change for one of your languages.

Observe that the restriction rule implies that you cannot use Whitespace as one of your languages, as removing any non-whitespace character won't change the behaviour of the Whitespace program.

Here's a simple example of a program that fulfills all the above restrictions, for the languages Python 2 and Python 3:

print("Hello World!")

Removing any character in print will cause both languages to throw a NameError; removing any bracket or quote will throw a SyntaxError, and removing any of the string characters will change the output in both languages. (Note that print("hello", "world") is a more subtle, but still valid program under the above rules).

This example is a bit lame because Python 2 and Python 3 are very similar, so I won't accept any other solutions that only use different versions of the same language (especially Python 2 and Python 3).

Answer 1

Bash + GolfScript + CJam

"echo" []
{ cat<&3;} \
3<""<("echo" 'p'~)

Output

Bash:

[]
p~

GolfScript:

"echo"
echo{ cat<&3;}0

CJam:

echo{ cat<&3;}-1echop

There is a \x7f in the end of output of CJam.

Answer 2

Bash + Befunge

"echo" $,$,"ol":,,,@

prints 'hello' in befunge.

Answer 3

GolfScript + PHP + CJam + Mathematica + bc + Pyth + /// + TI-Basic + R + Octave + Matlab + Scilab + Numeric Topline + ?Fueue + huh?

10

In Golscript, PHP, CJam, Mathematica, bc, Pyth, ///, and TI-Basic, it outputs 10.

In R, it outputs [1] 10

In Octave, it outputs ans = 10

In Matlab and Scilab, it outputs ans = 10.

In Numeric Topline, it outputs 0.

If I understand Fueue properly, it outputs a newline, then acts as a cat program.

In huh?, it outputs

What?
?

Answer 4

bc, GolfScript, Homespring, huh, Octave, Scilab (0 bytes)

Guaranteed to comply with rule 4. Not a winner, but would do well in the tie break.

Output

bc

Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.

GolfScript

Homespring

In Homespring, the null program is not a quine.

huh

?

Octave

GNU Octave, version 3.6.4
Copyright (C) 2013 John W. Eaton and others.
This is free software; see the source code for copying conditions.
There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  For details, type `warranty'.

Octave was configured for "x86_64-redhat-linux-gnu".

Additional information about Octave is available at http://www.octave.org.

Please contribute if you find this software useful.
For more information, visit http://www.octave.org/get-involved.html

Read http://www.octave.org/bugs.html to learn how to submit bug reports.

For information about changes from previous versions, type `news'.

Scilab

Startup execution:
  loading initial environment

-->

Answer 5

Seems like this answer is not fully correct.
I partially fixed it, and going to improve the other part in a few days.

C++ & Javascript

The idea is:

void eval(bool="main=function(){alert('Hi from Javascript!')};puts=function(){};int=0");
int
main()
{
puts("Hi from C++!");
}

C++: http://codepad.org/SK2wbIDL
Javascript: Just copy code to the browser console

And a set of fixes to make it satisfy

(Restriction). The removal of any single non-whitespace character from your code should cause your program to change its behaviour under every one of your languages. The program may "change" by becoming invalid for that language, or by changing the output that is produced.

From Javascript side:

Changing int, main or puts will crash with reading of undeclared variable. But bool and Hi from C++! can be safely changes. Let's fix it:

puts=function(){}

puts=function(s){s=='Hi from C++!'?bool:nope}

If strings are equal, it checks existance of bool, otherwice it crashes with undeclared nope.

Now, there are 2 trailing semicolons that can be removed. The first is fixed esyly - just remove newline before int:

void eval(bool="main=function(){alert('Hi from Javascript!')};puts=function(){};int=0");int

The second is before }, so I need some constriction, valid in both languages and not requiring semicolon at the end in C++ or forsing a semicolon in js. Fine:

while(0);

It's impossible to omit semicolon in js as while needs the body.

So the program at the moment is:

void eval(bool="main=function(){alert('Hi from Javascript!')};puts=function(s){s=='Hi from C++!'?bool:nope};int=0");int
main()
{
puts("Hi from C++!");while(0);
}

From C++ side:

There are 2 problems: eval can have any name and all js code can be changed.

I'll try to fix them in a few days.

Answer 6

CJam + Golfscript

Okay, this is somewhat boring, but it's a start.

1,

Prints "0" in both languages. Removal of the 1 causes an error, removing the , prints "1" instead.

The same can be done with 1) or 1(. There are many alternatives.

(Yes, I know this isn't code-golf)

Answer 7

C and C++

#include <stdio.h>
int main() { puts("Hello!"); return 0; }

C and C++ are different languages that are almost compatible with each other - contrary to what you might hear C++ is not a superset of C. Look at http://en.wikipedia.org/wiki/Compatibility_of_C_and_C%2B%2B for some differences. The example above is not idiomatic C++ but it does work and produces the same output in both C and C++.

Answer 8

JavaScipt, Lua, R and Python 3 - 24 bytes

May work on some other languages, I'll test latter.

alert=print;alert(1)

JavaScript was tested on Firefox's console and the other languages here, here and here

Answer 9

Perl + Ruby + Python

I think in PHP this would need a semicolon if you are running with -R.

print "Hello World!"

Answer 10

Bash + sh + zsh + ksh, 4 bytes:

echo

Really simple and satisfies every rule:

1. Outputs a newline in each of the languages.
2. Output currently does not vary in any way between the languages.
3. Does not produce an error in any of the languages...
4. ...except when any of the characters are removed/changed.

Answer 11

Bash + sh + zsh + ksh + Windows Batch, 4 bytes:

echo

Really simple and satisfies every rule:

Outputs a newline which doesn't vary in each of the languages (but Windows Batch, which outputs ECHO is on, on the language you use), doesn't error, except when any letter is removed or changed.

Answer 12

Every single flavor of HQ9+, 1 byte

9

Including but not limited to HQ9+, FishQ9+, BrainfishQ9+, CHIQRSX9+, Unified HQ9+, H9+, HQ9++,HQ9+-, FHQ9+-, HQ9F+, HQ9+B, HQ9+~, HQ9+2D, HI9+, and probably some more that I've missed.