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.

>>211
It's what I was talking about in >>200. A complex file format with a fairly rich structure and some compiled bytecode contained within it. The project was to make a tool that can translate/decompile it into readable/editable text which is then meant to be compiled back into the binary after editing, so basically a disassembler/assembler which can also go more high-level and act as a compiler/decompiler.

It wasn't the protobuff stuff, but it's similar enough that it would give you an idea about what you'd have to go through to implement something similar in C-like languages. Since the cost of doing a DSL in C is that high, it's just easier to give up and write the 10KLOC that just do the job directly, even though it would be a hack that you'd have to go through pain to maintain.