Write a polyglot that prints the language's name

Question

The task is to write a code which compiles in as many languages as possible, in as few characters as possible. To avoid trivial solutions, the program must print the name of the language it is compiled or interpreted in.

It has to work with at least 5 languages.

Scoring: (n is the number of languages)

(n * sqrt(n)) / code_length

The highest score wins, not sooner than 10 days after the first valid answer.

Answer 1

Bash, C, C++, Obj-C, Obj-C++, Perl, PHP, Ruby, 183 chars

score ~ 0.1236

For the C and C-like codes I owe a debt to @baby-rabbit. The others are inspired by the recognition that many languages have an eval statement that will grudgingly accept invalid syntax.

Outputs the language name to standard output. Sometimes generates a lot of error messages on standard error, so suppress them with 2>/dev/null as you run them.

#if 0
'PHP<?/*';eval "print\$=?'Perl':'Ruby';echo Bash";exit
__END__
#endif
#include <stdio.h>
main(){puts(
#ifdef __OBJC__
"obj-"
#endif
"C"
#ifdef __cplusplus
"++"
#endif
);}//*/?>'

The php solution outputs 'PHP' (including the single quotes), which may be bending the rules a little bit.

Last edit: shaved 12 chars from insight that $= is false in Ruby, 60 in Perl, and print$=?... is almost surely an error in Bash. Shaved 7 more from insight the Perl/Ruby/Bash test can now go into a single eval statement.

If the rules can tolerate more bending, I present this 8 language, 43 character solution (score 0.5262)

print("phperluarscriptrubypythoncatebg13");

for which the output includes the name of the interpreter for php, perl, lua, rscript, ruby, python, cat, and rot13.

Answer 2

C, C++, BF, BASH and Ruby; 280 chars (Score is about 0.040)

#include "stdio.h"
#define s "C"
#ifdef __cplusplus
#define s "C++"
#endif
#ifndef s
#"+++++++++[>++++++++++>+++++++++<<-]>>-.<++++.>-.++++++++.<----.>---.<+++++++.>---.++++++++.<<++++++++++.[-]"
if [ 1 == 2 ];then
puts "Ruby"
exit
fi
echo "BASH"
exit
end
#endif
main(){puts(s);}

Note that I am using a Linux system.

The code is run or compiled with the following commands (the file's name is test.c)

C:

gcc test.c

When run with ./a.out, output is C

C++:

c++ test.c

When run with ./a.out, output is C++

BASH:

./test.c

Outputs: BASH

Ruby:

ruby test.c

Outputs: Ruby

BrainF***:

Verified using the following:

• A JS debugger

• A free interpreter

• My interpreter

Outputs: brainfuck

Note that if the JS debugger is used, then the first two minus signs need to be removed. They were included to offset the plus signs in the string literal "C++". This was a very fun project, I'm working on adding more languages.

Just to add further clarity, here are my interpreter's/compiler's specs:

• gcc version 4.6.3

• ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]

• GNU bash, version 4.2.24(1)-release (x86_64-pc-linux-gnu)

SIDE NOTE

Using @baby-rabbit's trick I was able to extend my code to be executable in 7 languages (objective-C and objective-c++ being added). This is not my solution since I did copy some, but I thought I would show it off.

Update 9.12 Added SmallTalk run with gnu-smalltalk!

SmallTalk, C, C++, Objective-C, Objective-C++, BASH, BF, Ruby; 384 chars (Score: 0.059)

#if (a)
##(true) ifTrue: ['SmallTalk' printNl]
##(ObjectMemory quit)
#"+++++++++++[>++++++++++>+++++++++<<-]>>-.<++++.>-.++++++++.<----.>---.<+++++++.>---.++++++++.<<++++++++++.[-]"
if [ 1 == 2 ];then
puts 'Ruby'
exit
fi
echo 'BASH'
exit
end
=begin
#endif
#include "stdio.h"
main(){puts(
#ifdef __OBJC__
"Objective-"
#endif
"C"
#ifdef __cplusplus
"++"
#endif
);}
#ifdef b
=end
#endif

In the above code you will need to rename the file to produce the langauge's name for objective-c, obj-c++, c and c++.

Answer 3

Lua, Ruby, VimL, Sed, Befunge (129 chars; ~0.087 points)

Not sure if this one counts--the sed-part is embedded in the shebang line which is arguably a hack to get around the restriction. This also means that it should be run as an executable and not directly with sed.

I was lucky that all the other languages (sans Befunge) automagically ignores the shebang line (though apparently Ruby refuses to run the file if it has a shebang line that doesn't contain the string 'ruby' in it).

#!sed sanava;s/.*/sed/;q;ruby
--"".to_i#>"egnufeB">:#,_@
if 0
then
if IO
then
puts"Ruby"
else
print"Lua"
end
else
echo"VimL"
end

Sample usage:

% lua tmp/glot.poly
Lua
% ruby tmp/glot.poly
Ruby
% ./tmp/glot.poly
sed
% cfunge tmp/glot.poly       # Requires Befunge-98
Befunge

:source tmp/glot.poly        # from vim
VimL                         # displayed as message

Answer 4

BF, Bash, Batch, C, vi (163 characters; score ≈ .0686)

(<ESC> stands for ASCII code 27.)

rem (){ ((0));};true /*
rem ;goto(){ rem;}
rem ivi<ESC>ZZ'++++++++[>NUL ++++++++<NUL -]>NUL ++.++++.*/;main(){puts("C");}/*'
goto a
echo Bash
exit
:a
echo Batch
rem */

I tested this, as a batch file, with the MS-DOS 6.22 version of COMMAND.COM. By default, that interpreter mixes lines of source code with the output. To prevent that from happening, execute echo off before running the batch file.

To execute the vi code, which I have only tested using Vim, use the following command:

cat /dev/null > tmpfile && vi -s polyglot.sh tmpfile > /dev/null 2>&1 && cat tmpfile

Answer 5

bash, c, c++, obj-c, obj-c++; 134 chars; score=0.083

#if x
echo "bash"
exit
#endif
#include <stdio.h>
int main(){puts(
#ifdef __OBJC__
"obj-"
#endif
"c"
#ifdef __cplusplus
"++"
#endif
);}

rename file and run/compile as:

• sh file.sh
• cc file.c
• cc file.cpp
• cc file.m
• cc file.mm

(where cc is clang-421.10.42)

Answer 6

Bash, C, Gawk, Perl, vi (145 characters; score ≈ .077)

(<BS> stands for ASCII code 8. <ESC> stands for ASCII code 27.)

#define echo//<BS><BS><BS>vi<ESC>ZZ
#define BEGIN A()
#define B\
{
echo Bash ;exit;
#define C\
}
BEGIN {printf(A=="A"?"Perl":"Gawk");exit;}
main(){puts("C");}

To execute the vi code, which I have only tested using Vim, use this command:

cat /dev/null > tmpfile && vi -s polyglot.sh tmpfile > /dev/null 2>&1 && cat tmpfile

Answer 7

This is a cheap selection of languages, but here goes:

CoffeeScript, JScript, Mozilla Javascript (≈ JavaScript 1.3), ECMAScript Edition 5, ECMAScript Edition 3, 263 chars, score ≈ 0.043)

if(typeof arguments!="undefined")
 alert("CoffeeScript")
else if(typeof WScript!="undefined")
 WScript.echo("JScript")
else if(typeof uneval!="undefined")
 alert("Mozilla JavaScript")
else if(Array.prototype.map)
 alert("ECMAScript 5")
else
 alert("ECMAScript 3")