Hello SinDoc, what an interesting discussion! Whoo! ;-)
Many thanks four your comment. You wrote > So, if you have lazy-eval, there's no need for special-forms. This is obviousely correct for if / cond. Looking into the other special forms ( http://clojure.org/special_forms ), I wouldnt know how to implement all of them. Certainly there is, unknownst to me, a bunch of literature about (sets of) primitives that cannot e replaced - literature hints anybody? (Well, thats probably a nice set of exercises :) Thanky and regards, alux On 31 Mai, 12:45, "Sina K. Heshmati" <s...@khakbaz.com> wrote: > "alux" <alu...@googlemail.com> said: > > > I got a very basic question about the concept of "special form". What > > is correct, multiple selections allowed: > > > [ ] A special form is what can be implemented by a macro. > > Wrong. Macros cannot remove the need for special-forms, at least not in a > real interpreter. In a metacircular implementation, you can replace > special-forms with calls to the base-level implementation. For instance, if > you evaluate 'if' at base-level, then you can use it to define 'cond' at > base-level. > > > [ ] Every macro gives a special form. > > They can all be reduced to a number of expressions that cannot be implemented > by neither macros nor functions. > > These expressions can be evaluated using normal functions if you have lazy > evaluation of arguments. So, if you have lazy-eval, there's no need for > special-forms. > > > [ ] Only a macro that doesn't evaluate some of its arguments gives a > > special form. > > You could say that. > > > [ ] A special form is always built in, and cannot be implemented in > > the language itself. > > Unless you have lazy-eval. > > > [ ] Special forms are exactly the things that can be called, but dont > > evaluate all of their arguments. (Macros and build-ins, at least for > > eager languages.) > > > [ ] The concept of special form doesnt have anything to do with > > eagerness or lazyness. > > Wrong. It has everything to do with laziness. If you have one, you don't need > the other. > > Please note that, the concept of special-forms is a compromise and I don't > think anyone would want to have them. A language designer has to make a > choice as to whether to have special forms or not. If they don't want > special-forms, then they should provide lazy evaluation of arguments. > > Some introduce functional parameters in order to provide lazy evaluation of > arguments but that choice has its own trade-offs since it introduces a kind > of dynamic scoping. > > Kind regards, > SinDoc -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
