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 <[email protected]<javascript:>
> > 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
>> <[email protected]<javascript:>
>> > wrote:
>>
>>> Do you have target ns "clevolution.version.version0-1-1" required?
>>>
>>> -BG
>>>
>>> On Tue, Dec 18, 2012 at 1:38 PM, Alan Shaw <[email protected]<javascript:>>
>>> 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
>>> > <[email protected]<javascript:>>
>>> 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 <
>>> [email protected] <javascript:>>
>>> >> 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
>>> >>> <[email protected]<javascript:>>
>>> 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
>>> >>> > <[email protected] <javascript:>>
>>> >>> > 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
>>> >>> >> <[email protected]<javascript:>
>>> >
>>> >>> >> 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 <
>>> [email protected] <javascript:>>
>>> >>> >> > 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
>>> >>> >> >>> <[email protected] <javascript:>>
>>> >>> >> >>> wrote:
>>> >>> >> >>>>
>>> >>> >> >>>> Try (in-ns 'user-ns)
>>> >>> >> >>>>
>>> >>> >> >>>> Las
>>> >>> >> >>>>
>>> >>> >> >>>> On Dec 18, 2012 7:50 AM, "Alan Shaw"
>>> >>> >> >>>> <[email protected]<javascript:>>
>>> 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
>>> [email protected] <javascript:>
>>> >>> >> >>>>> Note that posts from new members are moderated - please be
>>> >>> >> >>>>> patient
>>> >>> >> >>>>> with
>>> >>> >> >>>>> your first post.
>>> >>> >> >>>>> To unsubscribe from this group, send email to
>>> >>> >> >>>>> [email protected] <javascript:>
>>> >>> >> >>>>> 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
>>> >>> >> >>>> [email protected]<javascript:>
>>> >>> >> >>>> Note that posts from new members are moderated - please be
>>> >>> >> >>>> patient
>>> >>> >> >>>> with
>>> >>> >> >>>> your first post.
>>> >>> >> >>>> To unsubscribe from this group, send email to
>>> >>> >> >>>> [email protected] <javascript:>
>>> >>> >> >>>> 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
>>> >>> >> >>> [email protected]<javascript:>
>>> >>> >> >>> Note that posts from new members are moderated - please be
>>> patient
>>> >>> >> >>> with
>>> >>> >> >>> your first post.
>>> >>> >> >>> To unsubscribe from this group, send email to
>>> >>> >> >>> [email protected] <javascript:>
>>> >>> >> >>> For more options, visit this group at
>>> >>> >> >>> 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
>>> >>> >> >> [email protected]<javascript:>
>>> >>> >> >> Note that posts from new members are moderated - please be
>>> patient
>>> >>> >> >> with
>>> >>> >> >> your first post.
>>> >>> >> >> To unsubscribe from this group, send email to
>>> >>> >> >> [email protected] <javascript:>
>>> >>> >> >> 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
>>> >>> >> > [email protected]<javascript:>
>>> >>> >> > Note that posts from new members are moderated - please be
>>> patient
>>> >>> >> > with
>>> >>> >> > your
>>> >>> >> > first post.
>>> >>> >> > To unsubscribe from this group, send email to
>>> >>> >> > [email protected] <javascript:>
>>> >>> >> > For more options, visit this group at
>>> >>> >> > 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
>>> >>> >> [email protected]<javascript:>
>>> >>> >> Note that posts from new members are moderated - please be patient
>>> >>> >> with
>>> >>> >> your first post.
>>> >>> >> To unsubscribe from this group, send email to
>>> >>> >> [email protected] <javascript:>
>>> >>> >> 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
>>> >>> > [email protected]<javascript:>
>>> >>> > Note that posts from new members are moderated - please be patient
>>> with
>>> >>> > your
>>> >>> > first post.
>>> >>> > To unsubscribe from this group, send email to
>>> >>> > [email protected] <javascript:>
>>> >>> > For more options, visit this group at
>>> >>> > 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
>>> >>> [email protected]<javascript:>
>>> >>> Note that posts from new members are moderated - please be patient
>>> with
>>> >>> your first post.
>>> >>> To unsubscribe from this group, send email to
>>> >>> [email protected] <javascript:>
>>> >>> 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 [email protected]<javascript:>
>>> > Note that posts from new members are moderated - please be patient
>>> with your
>>> > first post.
>>> > To unsubscribe from this group, send email to
>>> > [email protected] <javascript:>
>>> > For more options, visit this group at
>>> > 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 [email protected]<javascript:>
>>> Note that posts from new members are moderated - please be patient with
>>> your first post.
>>> To unsubscribe from this group, send email to
>>> [email protected] <javascript:>
>>> 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 [email protected]
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
