[Swift-devel] Re: [Swift-user] assigning file variables

[Ben Clifford]

On Fri, 27 Feb 2009, Michael Wilde wrote:

> The challenge will be to see in general how feasible it is to code in such a
> way that you always to a close via a procedure return. My guess is it will be
> feasible, but may lead to more procedures than a user might use in an
> imperative style.

I'd rather not force a separate procedure style; that's part of my 
argument for having iteration constructs that are sympathetic to single 
assignment analysis rather than being almost perfectly anti-sympathetic.

> related: whats a suggested debugging technique when "the next stage isnt
> running"? Thats exactly what happened to me, and one of the harder things in
> swift to debug.
> 
> I noticed by chance the other day that swift seems to read debugging commands
> of some sort from stdin? I may have missed it, but what are these, and can
> users use them to find the state of a stuck script?

There are two commands: v and t to show waiting variables and threads. I'm 
not sure how useful the output of that is in your case. Its not really a 
public interface, but you might be able to make sense of it.

There is much in place for easy debugging of dataflow-based hangs like 
this - previously, I've put effort into tightening the analysis so hangs 
don't happen, rather than into detecting and reporting hangs; and I'd like 
to continue in that trend (although at the moment, the next useful step 
there is to remove [index] based assignment entirely...)

--