[KazimirMajorinc]

In my opinion, dynamic scope is adequate solution for Lisp approach, i.e. expressive power on the first place. Newlisp is very simple and expressive dialect, and it is pleasure using it. Dynamic scope allow some things statical scope doesn't. Sure, the price for that expressive power is that one has to be more careful, but this is not really that hard, and it shouldn't be the problem to anyone who really accept basic Lisp ideas.

I can see how dynamic scope - just like dynamic typing, eval or macros - could be seen as problem for people who want language like, say, Ada that puts safety on the first place. It is legitimate position. But it is not design goal or tradition of Lisp. Lisp is designed for AI, exploratory programming, hacking, expressive power, adventure. Owner of this site, Paul Graham, frequently wrote in that vein. It is simply not consistent to brag about expressive power of Lisp, and then turn into safety freak when one mentions dynamic scope.

OK safety freak is maybe too strong, but you get the point.

[pg]

Dynamic scope is a decrease in expressive power. You don't get closures.

[plinkplonk]

PG on newLisp a long time ago

"I took a quick look at it. It looked to me as if the way you're supposed to avoid variable capture is to use variables with unusual names. Is this really the plan? What about expansions that occur within expansions?"

http://lambda-the-ultimate.org/node/257#comment-1889

[KazimirMajorinc]

There are few ways out of that:

1. use of "contexts" i.e. Newlisp namespaces

2. use of same approach as in CL or Scheme macros. In CL it is automatic generation of unusual names, gensyms, in Scheme it is even more automatic "hygiene". Both of these approaches are available in Newlisp as well. One can check my blog post at: http://kazimirmajorinc.blogspot.com/2009/12/symbols-as-sexpr... It is not simple reading if one didn't used dynamic scope, but essentially it is how one can write hygienic fexprs (Newlisp macros are actually fexprs).

3. use of some "OO" additions. I am bit of OO sceptic, but for those who are not, there are at least two OO systems for Newlisp.

3.1. Official FOOP system, still in development http://newlispfanclub.alh.net/forum/viewtopic.php?f=2&t=...

3.2. Greg's OO system http://www.taoeffect.com/blog/2009/12/introducing-objective-...

[KazimirMajorinc]

Closures are the functions with "private" data preserving values between two calls of the same function. It is not impossible with dynamic scope - but problem is again accidental name clash. As it is the same problem as with macros - I guess it can be solved on similar way - using functions with generated unusual and unique names of variables.

On the other side, with dynamic scope, functions are as expressive (or almost) as macros and they are the first class values. For example, one can implement "if" as a function. http://kazimirmajorinc.blogspot.com/2009/01/two-definitions-...