Re: how do I evaluate this lazy sequence?
> I'm just a
> bit amazed that you would go away and write clojure code to consume JSON
> and all that, without realising that data-structures in Clojure are
> immutable!
That part is obvious enough, but I thought the new data structures
returned from assoc were being handed to map which then, in turn,
returned a new data structure where all values had been updated with
the values from assoc. But clearly, I got the syntax badly wrong.
On Sep 27, 2:21 pm, "Jim - FooBar();" wrote:
> the 2 previous responses answered your question perfectly ...I'm just a
> bit amazed that you would go away and write clojure code to consume JSON
> and all that, without realising that data-structures in Clojure are
> immutable! I think we can all agree they are *the* cornerstone of
> Clojure. It is a bit alien at first but it does pay off in the long
> run... If you absolutely need to stick with your code style (mutability
> not-recommended in general) use a java HashMap instead...
>
> Jim
>
> ps: i recently used a cheshire without any problems :-)
>
> On 27/09/12 18:53, gaz jones wrote:
>
>
>
>
>
>
>
> > Couple of initial things, Clojure has immutable data structures so
> > when you call for example 'assoc' it will return you a new map with
> > the new values assoc'd. It will not mutate the original, so:
>
> > (let [foo {}]
> > (assoc foo :a 1)
> > (assoc foo :b 2)
> > foo)
>
> > Will return {}. You need to do something like:
>
> > (-> {}
> > (assoc :a 1)
> > (assoc :b 2))
>
> > => {:a 1 :b 2}
>
> > FYI, assoc takes multiple kvps:
>
> > (assoc {} :a 1 :b 2)
>
> > Also, to return valid JSON, you cannot simply call 'str' on the map.
> > You need to use a library likehttps://github.com/dakrone/cheshireor
> >https://github.com/clojure/data.jsonand encode the map as JSON.
>
> > Perhaps you could illustrate the data structure you are holding inside
> > of @registry, and the structure of the JSON you would like to emit.
> > Laziness is not an issue here.
>
> > On Thu, Sep 27, 2012 at 12:02 PM, larry google groups
> > wrote:
> >> I would like 2 types of advice:
>
> >> 1.) an answer to this specific question
>
> >> 2.) advice on how one is suppose to debug mysteries likes this
>
> >> I have a simple web app that serves some data (hopefully in JSON
> >> format, but at the moment I will accept anything at all). The app uses
> >> Ring and Moustache and outputs the data.
>
> >> We start with a simple atom:
>
> >> (def registry (atom {}))
>
> >> We put some data in this atom. And then we output it. But I have had
> >> great difficulty getting anything to appear on the screen. Assuming
> >> the problem was with the fact the main sequence was lazy, I added in
> >> doall everywhere it made sense. But I still can not get anything to
> >> work:
>
> >> (defn current-users [request]
> >> "The default action of this app. Add new users to the registry, and
> >> delete the ones that are more than 15 seconds old"
> >> (let [this-users-params (:params request)
> >> final-map-for-output {}]
> >> (add-to-logged-in-registry this-users-params)
> >> (remove-old-registrants)
> >> (response (apply str (into {}
> >> (doall
> >> (map (fn [each-user-map]
> >> (doall
> >> (let [inner-details (second each-
> >> user-map)]
> >> (assoc final-map-for-output
> >> "username" (get inner-details "username" "nothing found for user"))
> >> (assoc final-map-for-output
> >> "updated" (get inner-details "updated" "nothing found for updated"))
> >> final-map-for-output)))
> >> @registry)))
>
> >> The various variations I have tried on this have either given me a
> >> blank white page or:
>
> >> {}
>
> >> Nothing else.
>
> >> I used to do simply:
>
> >> (response (apply str (doall @registry)
>
> >> This worked fine. But it did not output valid JSON, so I wanted to
> >> change the format. But I have not been able to get anything to appear
> >> on screen.
>
> >> Suggestions?
>
> >> --
> >> 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
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Re: how do I evaluate this lazy sequence?
the 2 previous responses answered your question perfectly ...I'm just a
bit amazed that you would go away and write clojure code to consume JSON
and all that, without realising that data-structures in Clojure are
immutable! I think we can all agree they are *the* cornerstone of
Clojure. It is a bit alien at first but it does pay off in the long
run... If you absolutely need to stick with your code style (mutability
not-recommended in general) use a java HashMap instead...
Jim
ps: i recently used a cheshire without any problems :-)
On 27/09/12 18:53, gaz jones wrote:
Couple of initial things, Clojure has immutable data structures so
when you call for example 'assoc' it will return you a new map with
the new values assoc'd. It will not mutate the original, so:
(let [foo {}]
(assoc foo :a 1)
(assoc foo :b 2)
foo)
Will return {}. You need to do something like:
(-> {}
(assoc :a 1)
(assoc :b 2))
=> {:a 1 :b 2}
FYI, assoc takes multiple kvps:
(assoc {} :a 1 :b 2)
Also, to return valid JSON, you cannot simply call 'str' on the map.
You need to use a library like https://github.com/dakrone/cheshire or
https://github.com/clojure/data.json and encode the map as JSON.
Perhaps you could illustrate the data structure you are holding inside
of @registry, and the structure of the JSON you would like to emit.
Laziness is not an issue here.
On Thu, Sep 27, 2012 at 12:02 PM, larry google groups
wrote:
I would like 2 types of advice:
1.) an answer to this specific question
2.) advice on how one is suppose to debug mysteries likes this
I have a simple web app that serves some data (hopefully in JSON
format, but at the moment I will accept anything at all). The app uses
Ring and Moustache and outputs the data.
We start with a simple atom:
(def registry (atom {}))
We put some data in this atom. And then we output it. But I have had
great difficulty getting anything to appear on the screen. Assuming
the problem was with the fact the main sequence was lazy, I added in
doall everywhere it made sense. But I still can not get anything to
work:
(defn current-users [request]
"The default action of this app. Add new users to the registry, and
delete the ones that are more than 15 seconds old"
(let [this-users-params (:params request)
final-map-for-output {}]
(add-to-logged-in-registry this-users-params)
(remove-old-registrants)
(response (apply str (into {}
(doall
(map (fn [each-user-map]
(doall
(let [inner-details (second each-
user-map)]
(assoc final-map-for-output
"username" (get inner-details "username" "nothing found for user"))
(assoc final-map-for-output
"updated" (get inner-details "updated" "nothing found for updated"))
final-map-for-output)))
@registry)))
The various variations I have tried on this have either given me a
blank white page or:
{}
Nothing else.
I used to do simply:
(response (apply str (doall @registry)
This worked fine. But it did not output valid JSON, so I wanted to
change the format. But I have not been able to get anything to appear
on screen.
Suggestions?
--
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Re: how do I evaluate this lazy sequence?
Couple of initial things, Clojure has immutable data structures so
when you call for example 'assoc' it will return you a new map with
the new values assoc'd. It will not mutate the original, so:
(let [foo {}]
(assoc foo :a 1)
(assoc foo :b 2)
foo)
Will return {}. You need to do something like:
(-> {}
(assoc :a 1)
(assoc :b 2))
=> {:a 1 :b 2}
FYI, assoc takes multiple kvps:
(assoc {} :a 1 :b 2)
Also, to return valid JSON, you cannot simply call 'str' on the map.
You need to use a library like https://github.com/dakrone/cheshire or
https://github.com/clojure/data.json and encode the map as JSON.
Perhaps you could illustrate the data structure you are holding inside
of @registry, and the structure of the JSON you would like to emit.
Laziness is not an issue here.
On Thu, Sep 27, 2012 at 12:02 PM, larry google groups
wrote:
> I would like 2 types of advice:
>
> 1.) an answer to this specific question
>
> 2.) advice on how one is suppose to debug mysteries likes this
>
> I have a simple web app that serves some data (hopefully in JSON
> format, but at the moment I will accept anything at all). The app uses
> Ring and Moustache and outputs the data.
>
> We start with a simple atom:
>
> (def registry (atom {}))
>
> We put some data in this atom. And then we output it. But I have had
> great difficulty getting anything to appear on the screen. Assuming
> the problem was with the fact the main sequence was lazy, I added in
> doall everywhere it made sense. But I still can not get anything to
> work:
>
> (defn current-users [request]
> "The default action of this app. Add new users to the registry, and
> delete the ones that are more than 15 seconds old"
> (let [this-users-params (:params request)
> final-map-for-output {}]
> (add-to-logged-in-registry this-users-params)
> (remove-old-registrants)
> (response (apply str (into {}
> (doall
> (map (fn [each-user-map]
> (doall
> (let [inner-details (second each-
> user-map)]
> (assoc final-map-for-output
> "username" (get inner-details "username" "nothing found for user"))
> (assoc final-map-for-output
> "updated" (get inner-details "updated" "nothing found for updated"))
> final-map-for-output)))
>@registry)))
>
> The various variations I have tried on this have either given me a
> blank white page or:
>
> {}
>
> Nothing else.
>
> I used to do simply:
>
> (response (apply str (doall @registry)
>
> This worked fine. But it did not output valid JSON, so I wanted to
> change the format. But I have not been able to get anything to appear
> on screen.
>
> Suggestions?
>
> --
> 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
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Re: how do I evaluate this lazy sequence?
larry google groups writes: > We put some data in this atom. And then we output it. But I have had > great difficulty getting anything to appear on the screen. Assuming > the problem was with the fact the main sequence was lazy, I added in > doall everywhere it made sense. But I still can not get anything to > work: Your problem's here and has nothing to do with lazyness: > (let [inner-details (second each-user-map)] > (assoc final-map-for-output "username" (get inner-details > "username" "nothing found for user")) > (assoc final-map-for-output "updated" (get inner-details > "updated" "nothing found for updated")) > final-map-for-output))) assoc (and all clojure collection functions) doesn't modify the given map but it returns a new version of the given map with the new association. You simply don't use it. Maybe you want something like this in case you want to output pairs of "username"/inner-details, and "updated"/inner-details pairs. --8<---cut here---start->8--- (defn current-users [request] "The default action of this app. Add new users to the registry, and delete the ones that are more than 15 seconds old" (let [this-users-params (:params request)] (add-to-logged-in-registry this-users-params) (remove-old-registrants) (response (apply str (mapcat (fn [each-user-map] (let [inner-details (second each-user-map)] [["username" (get inner-details "username" "nothing found for user")] ["updated" (get inner-details "updated" "nothing found for updated")]])) @registry) --8<---cut here---end--->8--- Bye, Tassilo -- 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
how do I evaluate this lazy sequence?
I would like 2 types of advice:
1.) an answer to this specific question
2.) advice on how one is suppose to debug mysteries likes this
I have a simple web app that serves some data (hopefully in JSON
format, but at the moment I will accept anything at all). The app uses
Ring and Moustache and outputs the data.
We start with a simple atom:
(def registry (atom {}))
We put some data in this atom. And then we output it. But I have had
great difficulty getting anything to appear on the screen. Assuming
the problem was with the fact the main sequence was lazy, I added in
doall everywhere it made sense. But I still can not get anything to
work:
(defn current-users [request]
"The default action of this app. Add new users to the registry, and
delete the ones that are more than 15 seconds old"
(let [this-users-params (:params request)
final-map-for-output {}]
(add-to-logged-in-registry this-users-params)
(remove-old-registrants)
(response (apply str (into {}
(doall
(map (fn [each-user-map]
(doall
(let [inner-details (second each-
user-map)]
(assoc final-map-for-output
"username" (get inner-details "username" "nothing found for user"))
(assoc final-map-for-output
"updated" (get inner-details "updated" "nothing found for updated"))
final-map-for-output)))
@registry)))
The various variations I have tried on this have either given me a
blank white page or:
{}
Nothing else.
I used to do simply:
(response (apply str (doall @registry)
This worked fine. But it did not output valid JSON, so I wanted to
change the format. But I have not been able to get anything to appear
on screen.
Suggestions?
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
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Note that posts from new members are moderated - please be patient with your
first post.
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For more options, visit this group at
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