Author:

• Name: David Goodenough
  Location: US - United States of America (United States)

To build:

    make all

To use:

    echo foo bar | ./dg

Try:

    ./try.sh

Judges’ remarks:

Some C preprocessors got confused about single quotes in certain cases. In particular, the following source line:

    b12(ase(bco(acp(bi(acp(bcp(acp(bpl(aqu(bqu(A))))))))))))))))))))))))))))))

sometimes has to be changed to:

    b12(ase(bco(acp(bi(acp(bcp(acp(bpl('A'))))))))))))))))))))))))))))

particularly if the C preprocessor botches single quotes in cpp expansions, which we have done for the wider audience.

Author’s remarks:

If my preprocessor could hack it, I could write this as one single line rather than 4, but when I do that I get a complaint “defines nested too deeply”.

NOTICE to those who wish for a greater challenge:

If you want a greater challenge, don’t read any further: just try to understand the program via the source.

If you get stuck, come back and read below for additional hints and information.

How this entry works:

This is another rot13 job (believe it or not) - the #defines are a novel way of adding tokens: #define b12(x) 12 x means that at some point in the source a 12 is followed by the compressed nested #defines. The b12 gets the previous compression as an argument, and prepends the 12, thus making another step in the recreation of the source. The axx() #defines do the same, but add tokens after.

As for the rot13 algorithm, it relies on index(3) to find if the character is in the set A-Za-z. l[] is an array that gets filled with:

    "nopqrstuvwxyzzzzabcdefghijklmmmmNOPQRSTUVWXYZZZZABCDEFGHIJKLMMMM"

If index(3) says the char is in the alphabet, then XOR the offset with 16 to translate, and output, otherwise pass it unchanged.

Primary files

• dg.c - entry source code
• Makefile - entry Makefile
• dg.orig.c - original source code
• try.sh - script to try entry

Secondary files

• 1990_dg.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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