
readline: allocates a line and returns it; empty lines return NULL

expand_vars: (recursively) expand expressions of the form $X
	     frees the input line, allocates a new one.
	     returns NULL on error (including NULL input)

expand_vectors: expand expressions of the form $X
	     frees the input line, allocates a new one.
	     returns NULL on error (including NULL input)

parse performs math expansion on the line, returning a new line (old one is freed)


in newmath:

isolate_elements converts argc,argv to cstack,Ncstack (argc,argv NOT freed)
convert_to_RPN takes cstack,Nstack and converts to stack,Nstack; input cstack,Ncstack are freed
check_stack puts pointers to data types on stack, no data allocated
evaluate_stack 


command parses a single input line (line) and expands

