On 14/08/2012, at 4:45 PM, Dobes Vandermeer wrote:
> > Excellent idea. Type safe macros for table generation over heterogenous
> > types!
>
>
> You can try this. You will have a lot of pain!
> It has to be done in the parser (don't use "for", use "tuplefor" to avoid
> hassles parsing).
>
> Hmm yeah maybe I haven't dug into the compiler architecture much yet.
>
> I don't think it would work at the parser level since the type of the tuple
> has to be known.
Yes yes, that's not the point. The parser isn't doing the unrolling, its
generating
classes with a virtual procedure and instances that will do the unrolling.
You can do what you want now, but you have to write
class myfor[T] { virtual proc P: T; }
instance[T,U] myfor[T ** U] { ... }
instance[T,U] myfor [T * U} { ... }
for every such loop. The parser would just do all that housekeeping for you.
The body of the loop is the procedure P (with a tail call to P[U] to make
the polyjmorphic recursion happen).
> So it would have to be done at a later stage. I don't know how yet, maybe
> I'll give up before I get there.
As above. Look at
lib/std/tuple.flx
This deals with a function like "str" on a tuple.
Just replace "str" with "P" where P is the body of the loop.
--
john skaller
skal...@users.sourceforge.net
http://felix-lang.org
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