How to write hello-world in both Java and C++

This blog post explains hwo to write a hello-world program which compiles in both Java and C++.

The following solution makes use of the language difference that //...\ continues the one-line comment in C++, but not in Java.

//\
class t{public static void main(String[]a){System.out.print/*
#include<stdio.h>
int main(){if(1){return!printf//*/
("Hello, World!\n");}}

Multilingual programs in Haskell, Prolog, Perl and Python

This blog posts shows program source codes that work in multiple languages (including Haskell, Prolog, Perl, Perl and Python).

Here is a program which works in Haskell, Prolog and Perl:

$ cat >m1.prg <<'END'
foo( {-1/*_} ) if!'*/%'; print "Hello, Perl!\n" if<<'-- */'
}). :- write('Hello, Prolog!'), nl, halt.
/* -} x) = x
main = putStrLn "Hello, Haskell!"
-- */
END
$ perl m1.prg
Hello, Perl!
$ swipl -f m1.prg
Hello, Prolog!
$ cp m1.prg m1.hs
$ ghc m1.hs -o m1
$ ./m1
Hello, Haskell!

Here is a program which works in Haskell, Prolog and Python:

$ cat >m2.prg <<'END'
len( {-1%2:3} ); print "Hello, Python!"; """
}). :- write('Hello, Prolog!'), nl, halt.
/* -} x) = x
main = putStrLn "Hello, Haskell!"
-- """ # */
END
$ python m2.prg
Hello, Python!
$ swipl -f m2.prg
Hello, Prolog!
$ cp m2.prg m2.hs
$ ghc m2.hs -o m2
$ ./m2
Hello, Haskell!

It's possible to have polyglots of 8, 10 and even 22 programming languages, see them here.