[Nickle] Re: [AI] Nickle Growing Pains

[Carl Worth]

On Wed, 01 Dec 2004 00:28:16 -0800, Barton C Massey wrote:
> since all Nickle functions return a value.  It can
> be useful to use the void type with Nickle's disjoint
> union types.
> 
>   enum { a, b }
> 
> is shorthand for
> 
>   union { void a, void b }

The enum-as-disjoint-union is an interesting implementation detail,
but I would hope I could use enum types without having to know about
it.

> which should probably make your head hurt :-(.
> You can thus say things like
> 
>   typedef enum { a, b } e;
>   e v;
>   v.a = <>;
>   union switch(v) {
>   case a: printf("a\n"); break;
>   case b: printf("b\n"); break;
>   }  

The code above was written to demonstrate void and <>. Rewriting in a
more conventional enum style gives:

	typedef enum { a, b } e;
	e v;
	v = e.a;
	enum switch(v) {
	case a: printf("a\n"); break;
	case b: printf("b\n"); break;
	}

The "v = e.a" and "enum switch" syntax help hide the underlying
disjoint union quite well. But it leaks out quite badly with:

	> v
	a = <>

Can that be easily fixed to print "e.a" as expected?

-Carl