An approach that doesn't involve dynamic variables is to build, evaluate, and then call a function that's made out of the given code and takes an argument for the variable.
Assuming for the moment that the code is in symbolic form (rather than string form) like this: => (def exp 'a) #<Var@2dd1082f: a> Then you can do something like: => (let [a 0] ((eval (list 'fn '[a] exp)) a)) 0 It's easier to see why this is useful with a slightly more complex piece of code (but it could be anything): => (def exp '(+ a 100)) #<Var@2dd1082f: (+ a 100)> => (let [a 0] ((eval (list 'fn '[a] exp)) a)) 100 If your code really is in a string then you want to call read-string on it: => (def strexp "(+ a 100)") #<Var@45d1c3cd: "(+ a 100)"> => (let [a 0] ((eval (list 'fn '[a] (read-string strexp))) a)) 100 Of course the outermost "a"s here could and probably should be something else, since that'd be less confusing (I just used "a" to better match the original question): => (let [foo 0] ((eval (list 'fn '[a] (read-string strexp))) foo)) 100 -Lee On Jul 31, 2012, at 7:32 PM, Evan Mezeske wrote: > This thread on SO might be helpful: > http://stackoverflow.com/questions/6221716/variable-scope-eval-in-clojure . > > On Tuesday, July 31, 2012 2:02:30 PM UTC-7, Andrew wrote: > I have a value and a string. The string contains valid Clojure code and it > mentions a variable. I'd like to let-bind that variable to the value and then > evaluate the string. Can this be done? > > As a small example, I thought this would work: (let [a 0] (eval 'a))) > > Or maybe this: > user> (let [a 0] (eval 'user/a)) > > My initial attempt was this: (let [a 0] (eval (read-string "a"))) > > These all result in an exception... -- 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
