The last vector index must be an expression
is_vector_index wan't working correctly, it allowed using anything except vector variables as the last index, so you could do something like this (the error would be found on the C++ compiling phase):
DATA:
v is number vector
PROCEDURE:
display v:coso
In the process of fixing it I made a lot of changes. I deleted is_vector_index, split_vector now returns two parts (the vector and the index) and get_c_variable is simpler.