Hi, You can use expresso <https://github.com/clojure-numerics/expresso> for this: (use 'numeric.expresso.core) (def e (ex (+ 8 a (* 9 (+ 2 b)) 2))) ;=> (+ 8 a (* 9 (+ 2 b)) 2) This expression can now be manipulated by expresso to simplify it, solve it, etc. you can substitute a and b for its values when you know them and then evaluate (evaluate (substitute e '{a 1 b 2})) (or (evaluate e '{a 1 b 2}) which is equivalent) ;=> 47 But I think you are searching for compile-expr which turns the expression to a efficient clojure function taking the arguments ((compile-expr [a b] (+ a b)) 1 2) ;=> 3 In your example, you can get the partial evaluate behaviour by using optimize on the expression beforehand. optimize will do several transformations one of them is constant merging: (optimize e) ;=> (+ 10 a (* 9 (+ 2 b))) which can the compiled by compile-expr* (the function equivalent) (def partial-evaluated (compile-expr* '[a b] (optimize e))) (partial-evaluated 1 2) ;=> 47
Hope this helps M*aik* On Sat, Jun 14, 2014 at 1:43 AM, Christopher Small <metasoar...@gmail.com> wrote: > There is a nice example of something similar to this in Joy of Clojure > (2nd edition anyway; not sure about first). It only shows you how to do > contextual-evaluation, and doesn't return a function if some set of the > symbols are not mapped in the context, but I'll bet you could modify the > example to infer when one of the variables is missing in the context > specification, and return a function in that case. It is right at the > beginning of the section on macros. Good book, BTW. > > Can maybe share more later if you aren't interested in getting the book or > need more guidance on this. > > Chris > > > > On Friday, June 13, 2014 2:46:56 PM UTC-7, Dilvan wrote: >> >> Hi all, >> >> I'm a novice to Clojure (but not to programming). >> I'm looking for an implementation of an eval function to eval >> expression like Mathematica does. >> For instance, in Mathematica the expression: >> >> 8 + a + 9 (2 + b) + 2 >> >> if a and b are not bound, translates to >> >> Plus[10, a, Times[9, Plus[2, b]]] >> >> if a and b become bounded later (let say to 1 and 2) and the >> expression is evaluated again, it returns 47. >> >> I would like to be able to run: >> (eval-partial '(+ (+ 8 2) a (* 9 (+ 2 b)))) >> and get, if a and b are unbound: >> (fn [x y] (+ 10 x (* 9 (+ 2 y)))) >> or (better still) >> ['(a b) (fn [x y] (+ 10 x (* 9 (+ 2 y))))] >> Notice that, whenever possible, the eval takes place and parts of the >> expression are evaluated (in the example above, the expression (+ 8 2) is >> evaluated to 10). >> >> If you know of any implementation or have any ideas on the subject, >> please let me know. >> >> Cheers, >> Dilvan. >> >> > -- > 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. > -- 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.
