/prog/'s own esoteric language

Fun idea. Let's make our own programming language.
Conditions:
Must be somewhat useful like ABC.
Not limited to characters only. Can include words.
1 function per post.

NULL expansion:
If the preprocessor sees NULLx# where # is a non-negative integer it will be replaced with NULL # times.

Example:
foo(NULLx6);
expands to
foo(NULL, NULL, NULL, NULL, NULL, NULL);

NULLx0 is undefined.