Below, you can find another hint for the Challenge.
You should only get here after reading, digesting, and applying the .
Let us prepend '+ |' to S. Then we can extract
The output of this program is ():
which does not equal the program, but this output is a program that does output itself (; you can also run the preceding program, copy its output to the program area, and then click Challenge).
Finally, we constructed a program that satisfies all requirements of the Challenge. Can you summarize the main ingredients of the solution?
The adventure, however, is not over yet, because there are some further desires that crop up.
Can you think of some ways to improve the program?
Try your program in the machine, and see if you can extend it to an improved solution.
It is your turn ...
If you tried this hint, or do not see how it helps, then you are ready for the .