"In the old days, they say (I wasn't there), many Lisps had only special variables (are they really that special when they're all you have?). The problem is that bugs associated with the dynamic/special behavior are quite difficult to debug. You can have one part of the program affect another part and it isn't clear what the connection between the two is unless you're looking at the call graph."
> Have I missed an elegant solution that doesn't make the code bigger, harder to read or not thread-safe?
Perhaps CL style special variables? You can reference them without extra code (although you need naming conventions to prevent mixing lexical and special variables), and I think most CL implementations automatically make thread-local copies when using special variables in a thread. (See the rest of that article I linked above.)
>The problem is that bugs associated with the dynamic/special behavior are quite difficult to debug. You can have one part of the program affect another part and it isn't clear what the connection between the two is unless you're looking at the call graph.
Yep, that's a reasonable argument for a language designed
for average programmers. But if Arc is designed for
expert programmers then I think expert programmers will
want to make a different trade-off. I'll risk shooting
myself in the foot to get a more powerful language.
> Perhaps CL style special variables?
Yep, that would be good. That would be adding
dynamic binding to Arc.
