Hi Burt, I have done some investigation, further reducing your issue to the following:
(def g (make-adder 2)) (eval `(let [~'f ~g] (~'f 5))) ; --> error IllegalArgumentException No matching ctor found for class user$make_adder$fn__7609 etc. (defn h [x] (+ x 2)) (eval `(let [~'f ~h] (~'f 5))) ; --> 7 but it is still not completely clear to me why they behave differently hth, Gianluca On Thursday, January 14, 2016 at 11:05:55 AM UTC+1, Burt wrote: > > Hi, > > I got an exception using eval and I do not understand why! > Can anybody explain what happens? > > Here is a small piece of code showing the problem: > > (defn eval-phi [avec phi] > (eval `(let ~avec ~phi))) > > ; The idea of eval-phi is the evaluation of > ; arbitrary lists where the symbols are > ; defined in avec > > ; example: > ; in avec the symbol p is defined as true > ; and the symbol foo as a function adding 2 > > (def avec > ['p true > 'foo (fn [x] (+ 2 x))]) > > ; here are two lists > (def phi '(and p (= 7 (foo 5)))) > (def psi '(and (not p) (= 7 (foo 5)))) > > ; and here their evaluation > (eval-phi avec phi) > ; => true > (eval-phi avec psi) > ; => false > > ; second approach: > ; the attempt to give the definition of a > ; function in avec by a function which > ; returns a function leads to an exception: > > (defn make-adder [n] > (fn [x] (+ n x))) > > ((make-adder 2) 5) > ; => 7 > > ; here the second definition of a binding vector: > (def avec' > ['p true > 'foo (make-adder 2)]) > > (eval-phi avec' phi) > ; CompilerException java.lang.ExceptionInInitializerError > > ; in my mental model of the substitution of symbols by > ; their value there should be no difference between the > ; first approach and the second. > > ; Actually avec' contains the function returned by make-adder > ((nth avec' 3) 5) > ; => 7 > > ; Why does avec' leads to an exception? > > > *Kind regards,* > > *Burkhardt Renz* > > -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
