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)") >> (p/pprint (eval-in generator another-ns)) >> >> Hope it helps, >> >> Juan >> >> >> On Wednesday, December 19, 2012 1:13:00 AM UTC-3, nodename wrote: >>> >>> From yesterday: >>> >>> (defmacro eval-in >>> "Eval a Clojure form in a different namespace and switch back to >>> current namespace. >>> >>> Args: >>> code - Clojure form as string >>> ns - Target namespace as string" >>> [code ns] >>> `(do >>> (in-ns '~(symbol ns)) >>> (let [ret# (eval '~(read-string code))] >>> (in-ns '~(ns-name *ns*)) >>> ret#))) >>> >>> >>> >>> user=> (def generator "(X 400 400)") >>> #'user/generator >>> user=> (def image (eval-in generator "clevolution.version.version0-** >>> 1-1")) >>> CompilerException java.lang.ClassCastException: clojure.lang.Symbol >>> cannot be cast to java.lang.String, compiling:(NO_SOURCE_PATH:1) >>> >>> user=> (def image (eval-in "(X 400 400)" "clevolution.version.version0-* >>> *1-1")) >>> #'user/image >>> >>> So it's OK to pass the explicit string but not the symbol. What am I not >>> getting here? >>> >>> -A >>> >>> >>> On Tue, Dec 18, 2012 at 12:48 AM, Alan Shaw <node...@gmail.com> wrote: >>> >>>> Now I do, and the macro worked! >>>> I believe I have a problem using the macro from a function, but leaving >>>> that for tomorrow. >>>> >>>> Thanks BG! >>>> >>>> -A >>>> >>>> >>>> >>>> On Tue, Dec 18, 2012 at 12:19 AM, Baishampayan Ghose >>>> <b.g...@gmail.com>wrote: >>>> >>>>> Do you have target ns "clevolution.version.version0-**1-1" required? >>>>> >>>>> -BG >>>>> >>>>> On Tue, Dec 18, 2012 at 1:38 PM, Alan Shaw <node...@gmail.com> wrote: >>>>> > BG, >>>>> > The macro doesn't seem to do the trick. The function X is interned >>>>> in the >>>>> > target namespace, but: >>>>> > >>>>> > user=> (def image (eval-in "(X 400 400)" >>>>> > "clevolution.version.version0-**1-1")) >>>>> > CompilerException java.lang.RuntimeException: Unable to resolve >>>>> symbol: X in >>>>> > this context, compiling:(NO_SOURCE_PATH:1) >>>>> > >>>>> > >>>>> > On Mon, Dec 17, 2012 at 11:53 PM, Alan Shaw <node...@gmail.com> >>>>> wrote: >>>>> >> >>>>> >> Oh yes, the something.something is fixed so I can just prepend it, >>>>> thanks. >>>>> >> (Hadn't noticed your macro takes the ns as a string!) >>>>> >> >>>>> >> -A >>>>> >> >>>>> >> >>>>> >> >>>>> >> On Mon, Dec 17, 2012 at 11:47 PM, Baishampayan Ghose < >>>>> b.g...@gmail.com> >>>>> >> wrote: >>>>> >>> >>>>> >>> Alan, >>>>> >>> >>>>> >>> What you're asking for is to derive the ns "clojure.core" given >>>>> only >>>>> >>> "core". Not sure if that's possible. >>>>> >>> >>>>> >>> The namespace constitutes the whole dotted structure and not just >>>>> the >>>>> >>> last component, I am afraid. >>>>> >>> >>>>> >>> If the actual ns is something.something.version-0-**1-1, then you >>>>> need >>>>> >>> the string "something.something.version-**0-1-1" and not just >>>>> >>> "version-0-1-1" [unless of course you have some other way of >>>>> deriving >>>>> >>> it from info that's embedded in _your_ code or structure thereof]. >>>>> >>> >>>>> >>> >>>>> >>> -BG >>>>> >>> >>>>> >>> On Tue, Dec 18, 2012 at 1:10 PM, Alan Shaw <node...@gmail.com> >>>>> wrote: >>>>> >>> > Thanks BG, I'm trying that. >>>>> >>> > But I don't think it addresses how to get from the string >>>>> >>> > "version-0-1-1" to >>>>> >>> > the namespace something.something.version-0-**1-1. How can I do >>>>> that? >>>>> >>> > >>>>> >>> > -A >>>>> >>> > >>>>> >>> > >>>>> >>> > >>>>> >>> > On Mon, Dec 17, 2012 at 11:26 PM, Baishampayan Ghose >>>>> >>> > <b.g...@gmail.com> >>>>> >>> > wrote: >>>>> >>> >> >>>>> >>> >> Alan, >>>>> >>> >> >>>>> >>> >> Something like this might work for you - >>>>> >>> >> >>>>> >>> >> (defmacro eval-in >>>>> >>> >> "Eval a Clojure form in a different namespace and switch back >>>>> to >>>>> >>> >> current namespace. >>>>> >>> >> >>>>> >>> >> Args: >>>>> >>> >> code - Clojure form as string >>>>> >>> >> ns - Target namespace as string" >>>>> >>> >> [code ns] >>>>> >>> >> `(do >>>>> >>> >> (in-ns '~(symbol ns)) >>>>> >>> >> (let [ret# (eval '~(read-string code))] >>>>> >>> >> (in-ns '~(ns-name *ns*)) >>>>> >>> >> ret#))) >>>>> >>> >> >>>>> >>> >> Warning - I haven't really tested this code. >>>>> >>> >> >>>>> >>> >> -BG >>>>> >>> >> >>>>> >>> >> On Tue, Dec 18, 2012 at 12:37 PM, Alan Shaw <node...@gmail.com> >>>>> >>> >> wrote: >>>>> >>> >> > Thanks, Las! >>>>> >>> >> > >>>>> >>> >> > Ok say I have a file in which there is string such as >>>>> >>> >> > >>>>> >>> >> > "(- (atan (bw-noise 902 2 0.7604615575402431 400 400)) >>>>> >>> >> > (read-image-from-file >>>>> >>> >> > \"images/Dawn_on_Callipygea.**png\"))" >>>>> >>> >> > >>>>> >>> >> > and another >>>>> >>> >> > >>>>> >>> >> > "version-0-0-1" >>>>> >>> >> > >>>>> >>> >> > and I have a namespace version-0-0-1 into which functions >>>>> named atan >>>>> >>> >> > etc. >>>>> >>> >> > are all :referred. I want to evaluate the expression in that >>>>> >>> >> > particular >>>>> >>> >> > context, and not remain there when I'm done. >>>>> >>> >> > >>>>> >>> >> > -A >>>>> >>> >> > >>>>> >>> >> > >>>>> >>> >> > >>>>> >>> >> > On Mon, Dec 17, 2012 at 11:00 PM, László Török < >>>>> ltor...@gmail.com> >>>>> >>> >> > wrote: >>>>> >>> >> >> >>>>> >>> >> >> ah, sorry, it's a bit early for me >>>>> >>> >> >> >>>>> >>> >> >> (in-ns (ns-name user-ns)) >>>>> >>> >> >> >>>>> >>> >> >> if you could post a simple example for the second part of >>>>> your >>>>> >>> >> >> question >>>>> >>> >> >> I >>>>> >>> >> >> maybe able to help. >>>>> >>> >> >> >>>>> >>> >> >> Las >>>>> >>> >> >> >>>>> >>> >> >> Alan Shaw 2012. december 18., kedd napon a következőt írta: >>>>> >>> >> >> >>>>> >>> >> >>> Ah no, that puts me in a new user-ns namespace! Not what I >>>>> wanted! >>>>> >>> >> >>> >>>>> >>> >> >>> >>>>> >>> >> >>> On Mon, Dec 17, 2012 at 10:51 PM, László Török >>>>> >>> >> >>> <ltor...@gmail.com> >>>>> >>> >> >>> wrote: >>>>> >>> >> >>>> >>>>> >>> >> >>>> Try (in-ns 'user-ns) >>>>> >>> >> >>>> >>>>> >>> >> >>>> Las >>>>> >>> >> >>>> >>>>> >>> >> >>>> On Dec 18, 2012 7:50 AM, "Alan Shaw" <node...@gmail.com> >>>>> wrote: >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> user=> *ns* >>>>> >>> >> >>>>> #<Namespace user> >>>>> >>> >> >>>>> user=> (def user-ns *ns*) >>>>> >>> >> >>>>> #'user/user-ns >>>>> >>> >> >>>>> user=> user-ns >>>>> >>> >> >>>>> #<Namespace user> >>>>> >>> >> >>>>> user=> (in-ns user-ns) >>>>> >>> >> >>>>> ClassCastException clojure.lang.Namespace cannot be cast >>>>> to >>>>> >>> >> >>>>> clojure.lang.Symbol clojure.lang.RT$1.invoke >>>>> (RT.java:226) >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> It appears I'm not understanding how namespaces are >>>>> represented. >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> Also, is it just wrong of me to want to remember a >>>>> namespace I >>>>> >>> >> >>>>> was >>>>> >>> >> >>>>> working in and try to go back to it later? >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> The slightly larger context is: I'm saving an >>>>> s-expression with >>>>> >>> >> >>>>> unqualified names in it into a file as a string. Also >>>>> saving a >>>>> >>> >> >>>>> string >>>>> >>> >> >>>>> indicating the name of the environment in which that >>>>> string >>>>> >>> >> >>>>> should >>>>> >>> >> >>>>> be (read >>>>> >>> >> >>>>> and) eval'ed so that the names will resolve to the >>>>> appropriate >>>>> >>> >> >>>>> functions. >>>>> >>> >> >>>>> Advice on managing this would be appreciated. >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> -Alan Shaw >>>>> >>> >> >>>>> >>>>> >>> >> >>>>> -- >>>>> >>> >> >>>>> You received this message because you are subscribed to >>>>> the >>>>> >>> >> >>>>> Google >>>>> >>> >> >>>>> Groups "Clojure" group. >>>>> >>> >> >>>>> To post to this group, send email to >>>>> clo...@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+u...@**googlegroups.com >>>>> >>> >> >>>>> For more options, visit this group at >>>>> >>> >> >>>>> http://groups.google.com/**group/clojure?hl=en<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 >>>>> clo...@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+u...@**googlegroups.com >>>>> >>> >> >>>> For more options, visit this group at >>>>> >>> >> >>>> http://groups.google.com/**group/clojure?hl=en<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 >>>>> clo...@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+u...@**googlegroups.com >>>>> >>> >> >>> For more options, visit this group at >>>>> >>> >> >>> http://groups.google.com/**group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> >>>>> >>> >> >> >>>>> >>> >> >> >>>>> >>> >> >> >>>>> >>> >> >> -- >>>>> >>> >> >> László Török >>>>> >>> >> >> >>>>> >>> >> >> -- >>>>> >>> >> >> You received this message because you are subscribed to the >>>>> Google >>>>> >>> >> >> Groups "Clojure" group. >>>>> >>> >> >> To post to this group, send email to clo...@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+u...@**googlegroups.com >>>>> >>> >> >> For more options, visit this group at >>>>> >>> >> >> http://groups.google.com/**group/clojure?hl=en<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 clo...@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+u...@**googlegroups.com >>>>> >>> >> > For more options, visit this group at >>>>> >>> >> > http://groups.google.com/**group/clojure?hl=en<http://groups.google.com/group/clojure?hl=en> >>>>> >>> >> >>>>> >>> >> >>>>> >>> >> >>>>> >>> >> -- >>>>> >>> >> Baishampayan Ghose >>>>> >>> >> b.ghose at gmail.com >>>>> >>> >> >>>>> >>> >> -- >>>>> >>> >> You received this message because you are subscribed to the >>>>> Google >>>>> >>> >> Groups "Clojure" group. >>>>> >>> >> To post to this group, send email to clo...@googlegroups.com >>>>> >>> >> Note that posts from new members are moderated - 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