On 27 сен, 16:45, Mark Rathwell <mark.rathw...@gmail.com> wrote: > > And in this case Closure compiler behave itself also unpredictably and > > quite the contrary: > > Where it must evaluate a symbol (like in this case), it doesn't. > > Symbols need to be namespace resolved in order to be evaluated > properly. This is something you need to be aware of, but it is not > unpredictable or contrary to any documentation. And again, in this > case, the evaluation of the plus symbol does not happen at macro > expansion, it happens at run time. The behavior here is the same > inside of and outside of a macro: > > user=> (def e '(5 + 2)) > #'user/e > user=> (eval `((nth '~e 1) (nth e 0) (nth e 2))) > 2 > user=> (eval `((nth (list ~@e) 1) (nth e 0) (nth e 2))) > 7 > > > Where it mustn't evaluate a symbol (argument of macro), it does. > > This has already been shown in several responses, the argument is not > being evaluated in macro expansion, it is being evaluated at runtime.
In this point I want to cite Clojure doc, that say nothing about expansion and runtime, once more: "..If the operator of a call is a symbol that names a global var that is a macro function, that macro function is called and is passed the /unevaluated/ operand forms. " So, when I write the macro function body, I expect that operands are unevaluated when my body is executed to get an expanded form (finally expanded), that will be executed afterward to get a result (at runtime, as you say). But this is not the case in the very first example: user=> (defmacro infix [e] `(let [[x# f# y#] ~e] (f# x# y#))) #'user/infix user=> (infix (5 + 4)) java.lang.ClassCastException: java.lang.Integer cannot be cast to clojure.lang.IFn (NO_SOURCE_FILE:0) I insist that expansion is not quite correct. Am I right? > Using macroexpand will help you to see what the expanded forms look > like and what namespace symbols are resolved to. -- 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
