Executable XML users challenge

provide any LISP macro with clear explanation of its structure and function
that is :
1.concise (max 10 lines)
2.does not have a C equivalent(at least not anything above 100 lines)
3.does not use any libraries or imported complex functions which are not in C
If you provide an exact explanation/commentary on what it does i'll try to make a C solution which
is equivalent to LISP one. If i fail to do so, LISP wins, if i provide a solution you can make another macro.
If all examples in the thread are provide with C equivalents, LISP loses.

>>205
If i was was designing languages everytime i program my productivity will be zero, since i would be designing the perfect language while the real  code, would be neglected, unoptimized mess which i would think of not as a living, running program but as bunch of meaningless strings my Perfect Language would transform into the perfect program.Of course since my Perfect language is so complex, only i could read it and only if don't forget the entire language.
i.e. your macro layer is inferior,convoluted version of void.h(which includes reusable functions) with arcane syntax you designed on the weekend out of LISPtration over the inability of LISP to achieve stuff normal languages can do without a separate sublanguage.