Oh! yes it does! -A
On Wed, Dec 19, 2012 at 6:39 PM, Dave Ray <dave...@gmail.com> wrote: > It does, right? > > > On Wednesday, December 19, 2012, Alan Shaw wrote: > >> But returning the evaluation was a requirement... >> >> >> On Wed, Dec 19, 2012 at 2:58 PM, Alan Shaw <noden...@gmail.com> wrote: >> >> No, there was no requirement that it be a macro. Thanks! >> >> -A >> >> >> >> On Wed, Dec 19, 2012 at 7:40 AM, Dave Ray <dave...@gmail.com> wrote: >> >> A function seems to work fine unless I don't understand your requirement: >> >> ; normal version that takes code forms and symbols >> (defn eval-in >> [code ns] >> (let [old (-> *ns* str symbol)] >> (try >> (in-ns ns) >> (eval code) >> (finally >> (in-ns old))))) >> >> ; sugary version that takes strings >> (defn eval-strs [code-str ns-str] >> (eval-in (read-string code-str) (symbol ns-str))) >> >> and now try it out: >> >> user=> (eval-strs "(def z 500)" "bar") >> #'bar/z >> user=> (in-ns 'bar) >> #<Namespace bar> >> bar=> z >> 500 >> >> Making this bullet-proof and deciding whether it's actually a good >> design is left as an exercise for the reader. >> >> Cheers, >> >> Dave >> >> On Tue, Dec 18, 2012 at 11:22 PM, Alan Shaw <noden...@gmail.com> wrote: >> > As an aside, I'm curious about whether this could have been implemented >> > without a macro. >> > >> > -A >> > >> > On Dec 18, 2012 11:06 PM, "Alan Shaw" <noden...@gmail.com> wrote: >> >> >> >> Thanks very much Juan, that's some good study material for me. >> >> >> >> -A >> >> >> >> On Dec 18, 2012 10:45 PM, "juan.facorro" <juan.faco...@gmail.com> >> wrote: >> >>> >> >>> The macro sees it arguments as symbols and does not resolve to the >> >>> corresponding var until evaluation, so the value for the local code >> var in >> >>> the macro is actually the symbol generator. >> >>> >> >>> The eval-in macro uses the read-string function to evaluate the code >> you >> >>> provide, this function expects a string but it's getting the symbol >> >>> generator instead, since that's what the macro got as a first >> argument. >> >>> >> >>> Here's a modified version of the eval-in macro, that delays the >> >>> evaluation of the call to read-string: >> >>> >> >>> (require '[clojure.pprint :as p]) >> >>> >> >>> (defmacro eval-in >> >>> [code ns] >> >>> `(do >> >>> (in-ns '~(symbol ns)) >> >>> (let [ret# (eval (read-string ~code))] ; This line was changed >> >>> (in-ns '~(ns-name *ns*)) >> >>> ret#))) >> >>> >> >>> (p/pprint (macroexpand '(eval-in generator "another-ns"))) >> >>> >> >>> Here's the output: >> >>> >> >>> (do >> >>> (clojure.core/in-ns 'another-ns) >> >>> (clojure.core/let >> >>> [ret__1879__auto__ >> >>> (clojure.core/eval (clojure.core/read-string generator))] ; The >> >>> unquoting of code resulted in the symbol generator >> >>> (clojure.core/in-ns 'test-eval) >> >>> ret__1879__auto__)) >> >>> >> >>> If you want to use a var as an argument for the code, you could >> resolve >> >>> the var before changing namespaces, delaying the read-string until >> the forms >> >>> evaluation: >> >>> >> >>> (ns another-ns) >> >>> >> >>> (defn X [w h] [w h]) >> >>> ;--------------------------- >> >>> (ns this-ns >> >>> (:require [clojure.pprint :as p])) >> >>> >> >>> (defmacro eval-in >> >>> [code ns] >> >>> `(let [code# ~code] >> >>> (in-ns '~(symbol ns)) >> >>> (let [ret# (eval (read-string code#))] >> >>> (in-ns '~(ns-name *ns*)) >> >>> ret#))) >> >>> >> >>> (def generator "(X 300 300)") >> >> -- > 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 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
