>>>>> On Wed, 25 May 2011 07:34:22 +0200, Pascal Costanza said: > > On 25 May 2011, at 04:51, Matthew D. Swank wrote: > > > I have implemented a small fexpr interpreter in Common Lisp based on > > Kernel http://web.cs.wpi.edu/~jshutt/kernel.html. Right now it's a Lisp > > 1, but I am considering trying to make it a more idiomatic extension of > > Common Lisp by making it a Lisp 2. > > > > Part of the Lisp 2-ness of the Common Lisp evaluator is that the car of > > a form must name a function, macro, or special form. This name is either > > a symbol bound in the function name space, or a lambda expression. > > However, Kernel just requires the car evaluate to a combiner (this is > > what Kernel calls a generic operator). Obviously, in a Lisp 2, a symbol > > would evaluate to the value bound to it in the function name space. > > However, consider the following: > > > > ((returns-a-function) arg arg ...) > > > > Would it be reasonable to allow this as a legal form as well? > > > > I'm not arguing Common Lisp should work this way, but I seems to make > > sense in the context of a Kernel like evaluator. > > _If_ (returns-a-function) indeed returns a function, then this could be > ok. But what if it doesn't return a function? What if it is a macro that > returns just a symbol? Do you want to risk that ((return-something) ...) has > a different meaning than (funcall (return-something) ...)? This is > potentially confusing and could lead to code that is hard to debug...
Maybe no harder than other Lisp-2's :-) It seems like an interesting extension of the term "Lisp-2" -- as well as just specifying different namespaces, the proposal is to have a different evaluator for the car of the form. In fact, CL already has one, but it is very limited. If that evaluator allows macro forms, then a macro that expands to a symbol should work as if the symbol was used directly. If you use such a macro with (funcall (return-something) ...), then you are using the regular evaluator for the macro form. -- Martin Simmons LispWorks Ltd http://www.lispworks.com/ _______________________________________________ pro mailing list pro@common-lisp.net http://lists.common-lisp.net/cgi-bin/mailman/listinfo/pro
