Crackle Pop!

I was recently challenged to write CracklePop in any language of my choice, here’re the program specifications:

Write a program that prints out the numbers 1 to 100. If the number is divisible by 3, print Crackle instead of the number. If it’s divisible by 5, print Pop. If it’s divisible by both 3 and 5, print CracklePop.

In an attempt to be original, I decided to implement it in two languages, but in one single file!

Let me explain the two tricks I used to achieve this.

Trick 1, back slash followed by new line character

At the beginning of the program, we’ll need a couple of lines that set up what’s required so the program works in C. These lines need to be ignored when running on Javascript.

That’s done with a back-slash at the end of the line, which is only evaluated by the C preprocessor, and will remove the new line character. Converting this:

/* This is CracklePop in C & Javascript *\
/#include <stdio.h>

Into this:

/* This is CracklePop in C & Javascript */#include <stdio.h>

This trick is used twice to run a couple of setup lines in C and another setup which is exclusive for Javascript.

That preprocessor feature is normally used for multi-line macros. Here’s the related GCC documentation.

Trick 2, language detection at run time

After our setup lines, the code is the same for both languages. So it must be valid syntax in both, but we can introduce control flow based on the current language. That’s needed in the call to printf, sorted out like this:

'R' == 82 ? printf("%i\n", i) : printf(i + '\n');

The expression 'R' == 82 has different meaning on each language:

In Javascript, 'R' is a string so it’s obviously not equal to 82. Therefore this is falsey.
In C, 'R' is a char. Specifically, it’s number 82 in the ASCII table, so this has a truthy result.

Ba Dum Tsss

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/* This is CracklePop in C & Javascript *\
/#include <stdio.h>
typedef int function; typedef int var;
//*///////////////////////////////////////////////////////////////////////////\
printf = function(a) { process.stdout.write(a) };
/*         Tested with LLVM v9.1.0 (clang), GCC v4.6.3 & Node v8.9.4         */

function cracklePop(a, b) {
  for (var i = a; i <= b; i++)
    if (i % 3 == 0 && i % 5 == 0) {
      printf("CracklePop\n");
    } else if (i % 3 == 0) {
      printf("Crackle\n");
    } else if (i % 5 == 0) {
      printf("Pop\n");
    } else {
      'R' == 82 ? printf("%i\n", i) : printf(i + '\n');
    }
}

function main() {
  cracklePop(1, 100);
} main();

Now that we’ve got so far writing a completely useless program with no real application, let’s not stop here. Out there, there’s a whole world of challenges like this.

If you enjoyed this fiddle, you should check out Yusuke Endoh’s quine relay, and his talk Esoteric, Obfuscated, Artistic Programming in Ruby.

I’ll finally wrap up this post leaving a challenge: Would it be possible to add a third language?