Re: [stack] stackless fixed-arity concatenative languages

On May 22, 2008, at 10:27 AM, William Tanksley, Jr wrote:

> That's what I meant by asking whether the problem was fundamental
> -- it appears that it wasn't; our problem was due to a foggy
> specification of bi@ that caused us to accept an incorrect
> implementation.

Well, to be clear, Cat and Fifth can't infer a good type for the  
correct version either. You end up with 'A b b (A b -> A) -> A'. It's  
the same general problem where the first application gets in the way  
of the second. This is directly related to the fact that you're doing  
all your computation on a single stack and the second application (in  
this case) is allowed access to the entire state of the program at the  
limit. This is what I meant by it being a fundamental problem for a  
system like Fifth's when n-ary combinators are involved.

With the newer (and not yet fully implemented) system, you can infer a  
good type with the clearer specification, but only because the type  
'$a [$B] -> $B $a $B' *is* the specification. It's somewhat concerning  
however that I need a system that will do whole program analysis if  
necessary in order to avoid making assumptions. Only more experience  
will tell if it's feasible in practice. I haven't been able to try it  
with anything but programs of a few lines yet.

- John