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.

>>117
If sort is a sorting function, it should
A.sort an array
B.provided array is a list of objects
If it does not the provided code is defective since no functionality is present.
If it does sort an "array" with strings and doubles the implementation is defective enough to allow such retarded code to be written.
And results of treating such "comparable objects" are bound to cause any sort of errors you cannot think from safe-from-type-casts language.