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.

>>250

The people who add things like foreach macros are trying to force it the wrong way(its not semantically wrong just lacks native support: i would want such thing supported only at the level of a language, not as a macro i would have to rely on), since they think container-specific functions are unelegant.

People like are trying to emulate an interator you fucking nob. Again, you wouldn't know something like this because you have never written an actual line of C code. Now tell us again why you want to introduce platform specific shit into the C standard you fucking idiot.