🚀 go-pugleaf

In <comp.std.c++> hildum@ntmtv.UUCP (Eric Hildum) writes:
>
>... C++ already allows duplicate codes

Yes, but the definitions are at least in one place, which makes the
code easier to maintain.  Never mind, I'm sure you are aware of the
potential problems.

I have implemented extensible enumerations with templates.  I think
the template sollution offers much of what you would like:

	- extensible set of enumerators
	- named enumerator symbols
	- type-safe, in the sense that an enumeration variable
	  may only be assigned enumerators of the corresponding
	  (possibly extended) enumeration

However, there are problems:

	- the template version is MUCH less efficient, at least
	  with current template implementations
	- these enumerators are not compile-time constants, so
	  they cannot be used as case labels, for example
	- compiler must allocate storage for enumerators
	- the scope of the enumerator may not match the scope
	  of the enumerated type, so garbage values may float
	  around in the system

It is possible to add additional logic to handle the last problem
listed above, but it does cost a little in run-time performance.

I did this excercise as part of the analysis of operator overloading
of enumerations (a C++ standardization issue).  I can post the actual
code if there is enough interest; it's just two pages of code.


		-- Dag