prog

Marvin Minsky - The Beauty of the Lisp Language

166 2020-10-12 16:54

>>164
Could you define a macro

#define_default OPEN_FUTURE LISP_HAS_IT

that expands into the following:

#if !defined(OPEN_FUTURE)
#define OPEN_FUTURE LISP_HAS_IT
#endif

i.e., define a macro to be a value only if it has not been defined yet. I think this is a practical use-case.