[Main]
Name=NULL_INDEX
Type=Constant
Header Files=basfunc.h, estack.h
Definition=#define NULL_INDEX ((CESI) 0)

[Description]
Describes an empty expression stack index.

[Explanation]
NULL_INDEX is an expression stack index (<A HREF="$$LINK(estack.h/ESI)">ESI</A>)
equivalent to <A HREF="$$LINK(alloc.h/NULL)">NULL</A>. It can be used as a
function argument in cases where the argument is optional.
