Pure virtual functions

[kiselgra]

There is currently no built-in way to specify pure-virtual functions. Also, virtual functions alone are clumsy:

(function foo () -> (virtual void) ...)

I'm not sure it this is the best solution, but what about

(virtual foo () -> void ...)

In this case we could also skip the whole fishing-for-=0 with

(pure-virtual foo () -> void)

(in contrast to (virtual ...) this cannot be done using macros alone, we'd have to add a node.

@lispbub Do you have other preferences/ideas?

[kiselgra]

I think I'd favour

(function foo -> (pure virtual ...) ...)

and we'd just require the list to start with pure virtual. Should be easy to check for.