Below, you can find another hint for the Challenge.
You should only get here after reading, digesting, and applying the .
In Hint 19 under b, an alternative was suggested for putting reference occurrences of markers in the blueprint, viz. to use multiple characters as marker. Let us explore this idea further.
One desire is to have the ability to use any character in the program, that is, not to block any characters from use because they act as marker. We must make use of markers for
We cannot use single characters as markers, because these would block those characters from regular use. Thus, we will have to use special character sequences as markers. We must have the ability to recognize those markers, without actually incorporating the marker sequence in the program (because the latter would constitute an occurrence of the marker, but it should not be transcribed). For instance, when using the special sequence NL, we should not write
because it contains an occurrence of NL (never mind that this sequence may be a bad choice) that will be transcribed erroneously (also see what happened in Hint 18). But we could write
because it contains no occurrence of NL. Note that && is the logical and-operator. Similarly, || is the logical or-operator (that is also the reason why we want the ability to use vertical bars in the program). Alternatively we could write
If we use multiple characters, we still need to decide which and how. Do you have an idea?
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 .