Component question/advice
Hello, I'm writing an app/system that subscribes to a number of feeds, the number and configuration of the feeds is a configurable run-time thing. Seems like I should have a Feed component, which is passed its config when instantiated. But having a named slot in the system for each feed would be painful and kinda defeats the point of having a variable number of feeds that get configured. How best to deal with this in Component? One thought I had was to create a Feeds (note plural, trailing s) component. The Feeds component would be instantiated with a collection of feed configs, and would have a single slot to hold the collection of instantiated feeds. This Feeds component would instantiate a Feed component for each feed, and could start/stop them in its own start/stop methods. I appreciate/understand that my individual Feed components would not be participating in the System dependency injection, but AFAICT they don't need to. The above seems like it would work fine, but also seems like it is not idiomatic Component. I would welcome any thoughts/advice as to how best to structure this with Component. Thanks Don -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/0caae21e-b7c0-422f-a157-15c535c84022%40googlegroups.com.
Re: [ANN] Throttler: a library for rate limiting
On May 16, 2014, at 11:11 PM, Bruno Vecchi vecch...@gmail.com wrote: As per having a random frequency between an interval, could you clarify a bit? Do you want the time between requests to be drawn randomly from some distribution each time? If that's the case, the best way I can think of would require a change in the implementation of the bucket filling go thread. Instead of doing: (timeout some-constant) it would have to do (timeout (sample distribution)) Or maybe even more generally just (timeout (gen-timeout)) where gen-timeout is just a function that returns a timeout value for the next function call. For the common case it would have to be `(constantly some-number)`. I like gen-timeout the best. It is the most general. -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [ANN] Throttler: a library for rate limiting
On May 14, 2014, at 9:43 AM, Bruno Vecchi vecch...@gmail.com wrote: Throttler[1] is a little library I wrote out of need for one of my personal projects. It lets you control the maximum rate of function calls or message transmissions through core.async channels. This is way cool, thanks for sharing it! A while back I needed something like this to throttle http requests, and I cobbled something together that used Thread/sleep, it worked, but vastly inferior to your library, AFAICT. I intent to throw out my code out and use your library. In my application, I would like to have a throttle-fn that was guaranteed not to occur faster than some number, but also want to add a (bounded) random number to that limit. For example, let's say I wanted my http requests to be no more frequent than every 5 seconds, but some random number of seconds between 5 seconds and 15 seconds. Is there any way to add/modify throttler to handle a case like that? In my application, I use clj-http to make http requests, and what I did was to create a wrap-throttle middleware and added that to the middleware stack for the (customized) http client I used for rate-limited requests. I am thinking that approach would work well with your throttle-fn Best regards, Don -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: Potential improvement to select-keys ?
On Nov 2, 2013, at 9:27 AM, Mark Engelberg mark.engelb...@gmail.com wrote:
I seem to be a relatively lone voice thinking it makes sense to preserve the
type of the map, and honestly, I'm not going to lose any sleep if this patch
is never actually implemented, but here's my two cents on the optimal
design for records.
Earlier in the thread, I mentioned two mental models about how select-keys
works. Even though the actual implementation involves starting from an empty
map and building back up, I think the behavior of select-keys should mimic
the mental model of discarding irrelevant keys.
The two mental models predict somewhat differently what would happen when
working with records. Records can hold additional keys. So imagine someone
dumps a whole lot of additional keys, and then wants to recover the
original, true record, by calling select-keys with the original keys in the
record. I think this is a use case worth supporting. This corresponds to
the mental model of discarding unwanted keys.
To implement this for records:
If any of the original record keys do not appear in the selected keys, then,
as with dissoc, we must revert back to a map as there is no valid way to
represent this as a record.
Otherwise, maintain the record type -- the core record contents are
preserved, and essentially you only need to call select-keys only on the
extended map of extra keys stored in the record.
I agree 100% with Mark’s comments above.
This is exactly the model I would expect select-keys to have.
Conceptually, this is how I imagine select-keys should work:
(defn select-keys++
Returns a new map of the same (hashed/sorted) type,
that contains only those entries whose key is in keyseq
[map keyseq]
(apply dissoc
map
(clojure.set/difference (set (keys map))
(set keyseq
I am not saying that this would be the best , or even a good, implementation.
Like Mark, I am not going to lose any sleep about this either, but I was using
Mark’s data.priority-maps the other day,
did a select-keys to winnow down my priority-map, and was surprised by the
result.
Perhaps I should not have been surprised….
In preparing this email, I carefully re-read the doc strings for both dissoc
and select keys:
(defn dissoc
dissoc[iate]. Returns a new map of the same (hashed/sorted) type,
that does not contain a mapping for key(s).”
(defn select-keys
Returns a map containing only those entries in map whose key is in keys
Clearly dissoc makes the promise to return a map of the same type that
select-keys doesn’t.
A potential non-code change to select-keys might be to emphasize that the
return map will be
a hash-map, regardless of the kind/type of input map.
Don
On Sat, Nov 2, 2013 at 8:49 AM, Andy Fingerhut andy.finger...@gmail.com
wrote:
I attached another patch to the ticket. It builds up the answer from the
empty map {} if the argument is a record (as the current select-keys does),
but from (empty map) if it is not a record, so it will preserve sortedness of
the argument. Not sure if there are any other cases that are a problem, or
if it does what everyone would expect, but it should be closer.
http://dev.clojure.org/jira/browse/CLJ-1287
Andy
On Sat, Nov 2, 2013 at 6:07 AM, Alex Miller a...@puredanger.com wrote:
One other point:
Sometimes people use sorted maps and array maps specifically for scenarios
in which the keys are not hashable and therefore hash maps would not apply.
Dumping the contents into a regular map in such cases doesn't make much
sense.
Everything is hashable, not sure what a non-hashable key means. Array maps
use the hash of the key to determine the array bucket. If you get the hash
code of a sorted map, it will get the hash of all keys and values.
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Potential improvement to select-keys ?
select-keys currently returns a regular hash-map, regardless of the kind of map provided as the input argument. Alternately, select-keys could call empty on it’s map argument to obtain the map it will return, thereby preserving the type of map provided. FYI, Mark Engelberg recently pushed a change to data.priority-map that ensures that the specific flavor of priority-map is preserved through calls to empty… -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Can a protocol method have the same name as a clojure.core function?
I'd like to name a protocol method to be the same name as a clojure.core function, for example, get. Is this possible, and if so, how? user= (ns ptest.protocol (:refer-clojure :exclude [get])) nil ptest.protocol= (defprotocol TestProtocol (get [_ key] Returns the contents of field :key) ) TestProtocol ptest.protocol= (ns ptest.core (:require [ptest.protocol :as testp]) (:refer-clojure :exclude [get])) ptest.core= (defrecord TF [a b ] testp/TestProtocol (get [this key] Doesn't work!)) CompilerException java.lang.ClassFormatError: Duplicate method namesignature in class file ptest/core/TF, compiling:(NO_SOURCE_PATH:1) -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: Can a protocol method have the same name as a clojure.core function?
That makes perfect sense, and I should have figured that out since defrecord is implementing a bunch of useful protocols underneath…. Thanks for the quick response! On Feb 7, 2013, at 9:38 PM, Ben Wolfson wolf...@gmail.com wrote: You just can't use defrecord, because defrecord macroexpands into a deftype that implements a *different* protocol with a function *also* named get. On Thu, Feb 7, 2013 at 9:24 PM, Don Jackson cloj...@clark-communications.com wrote: I'd like to name a protocol method to be the same name as a clojure.core function, for example, get. Is this possible, and if so, how? user= (ns ptest.protocol (:refer-clojure :exclude [get])) nil ptest.protocol= (defprotocol TestProtocol (get [_ key] Returns the contents of field :key) ) TestProtocol ptest.protocol= (ns ptest.core (:require [ptest.protocol :as testp]) (:refer-clojure :exclude [get])) ptest.core= (defrecord TF [a b ] testp/TestProtocol (get [this key] Doesn't work!)) CompilerException java.lang.ClassFormatError: Duplicate method namesignature in class file ptest/core/TF, compiling:(NO_SOURCE_PATH:1) -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out. -- Ben Wolfson Human kind has used its intelligence to vary the flavour of drinks, which may be sweet, aromatic, fermented or spirit-based. ... Family and social life also offer numerous other occasions to consume drinks for pleasure. [Larousse, Drink entry] -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out. -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Re: Why is there not much conversation on Spreadsheet like APIs in this group?
John, Thanks for your email and the links, I'm interested in this topic and wasn't aware of the previous work you referenced. I would't be surprised if the sentiments expressed by Stephen Compall in this thread, specially my Clojure style seeks immutable solutions, and cells-ishs don't fit in that category might be shared by many in the Clojure community. Just something to keep in mind, and it is certainly possible that I'm wrong about this. Important parts of the app I am currently working on definitely have a need to react to changes on dependent values Right now, unfortunately, I am attempting to manage the dependency graph and the resulting updates/propagations manually, which is tedious and prone to error. I'm actively looking for a solution that would automate some or all of this. I'm wondering if this kind of thing might work well in conjunction with the graph library recently released by Prismatic, and there are are similar work-alike libraries. One idea I am currently mulling over is compiling a computation specified in the graph manner into a dynamically updatable realization/implementation, somewhat similar to the way that Prismatic compiles their graphs into maps , lazy maps, or a map with each subcomputation spawned in parallel via futures. I'm definitely interested in talking/working with others with similar interests/requirements…. Don On Feb 3, 2013, at 1:39 AM, john john.vie...@gmail.com wrote: Hi, the library https://github.com/straszheimjeffrey/dataflow and http://richhickey.github.com/clojure-contrib/dataflow-api.html (1) or https://github.com/gcv/dgraph seems to me very cool for systems that need to react on changes on dependent values. I very much like the API in (1) Actually my personal opinion is that this is a very substantial thing in business applications. Am I wrong but nobody seems to bother about them? (I am not well clojure connected so this assumption is totally based on git-update-dates / clojure-user-group discussions / planet.clojure.in posts) -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
(into [] (take n v)) vs (subvec v 0 n)
In the app I am working on, I have a number of pre-computed,cached collections, and for each collection, I have an accessor function that returns either the entire collection or the first n elements. Currently the underlying collection is a vector, so I had something like this: (defn foo-accessor ([] foo-vector) ([n] (take n foo-vector))) It occurred to me that take returns a list, and so the type returned by my accessor was dependent on how it was called, I thought I would change that, and remembered subvec, so I substituted in subvec for take, like this: ([n] (subvec foo-vector 0 n)) That worked great until ( (count foo-vector) n), and I got an IndexOutOfBoundsException So, then without thinking much, I wrote (defn subvec-safe subvec fails if you specify an end that is greater than count. This version checks that, and DoesTheRightThing! ([v start] (subvec v start)) ([v start end] (if ( (count v) end) (subvec v start end) (subvec v start (count v) (Yes, it is safe ONLY for the end value…) And (defn takev take for a vector, returns a subvec or the vector itself. Uses subvec-safe so specifying a n longer than (count v) works [n vec] (subvec-safe vec 0 n)) Even before finishing takev, it occurred to me that (defn- takev take for a vector [n vec] (into [] (take n vec))) Might be easier/faster. subvec returns a clojure.lang.APersistentVector$SubVector whereas (into [] (take …)) returns a vector. Any thoughts on which of the above is better? Thanks, Don -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
Advice/recommendations for generating templated (non-Clojure) s-expressions?
Hello, I want to generate non-Clojure s-expressions in Clojure code, with a nice templating format (like syntax-quote provides), BUT with the option of providing my own methods/functions for resolving/processing symbols, and the ability to provide my own methods/functions for evaluating syntax-quote escapes, e.g. ~, @. Is there anything out there I can use? Here is some background: I have been playing around with generating SUO-KIF from Clojure code. ontolog.cim3.net/file/resource/reference/SIGMA-kee/suo-kif.pdf Here is an example SUO-KIF form: (= (instance ?COMPANY Coffeeshop) (exists (?SERVICE ?BEVERAGE) (and (instance ?SERVICE CommercialService) (agent ?SERVICE ?COMPANY) (instance ?SERVICE Selling) (patient ?SERVICE ?BEVERAGE) (instance ?BEVERAGE Coffee I'd like to generate the above via a Clojure macro/function that would be called like this: (sells Coffeeshop Coffee) By defining sells something like this: (defmacro-like-thing sells [kind-of-store product] `(= (instance ?COMPANY ~kind-of-store) (exists (?SERVICE ?PRODUCT)) … )) My initial thought was this was going to be completely trivial, and I'd be done in 30 minutes maximum and it is easy to generate something right away, but I am not at all happy with the result, especially what the Clojure code templates look like. It would be really nice if the resulting template would look very close to the resulting output, so that users of this tool (Ontologists, not programmers) could easily see/specify the templates. My first thought was that I would use Clojure macros and syntax-quote to generate the SUO-KIF s-expressions. To my way of thinking, syntax-quote is a very nice s-exp templating tool, what could be easier? I quickly re-learned that macros are a really about generating Clojure, at read time, that is then eval'ed. Two issues with that: 1) symbols in my template specification are resolved/namespace-qualified by syntax-quote, which is not what I want at all. 2) I don't want the resulting s-expression to be eval'ed by Clojure. I can work around that by having the the macro return (quote s-exp), I guess. I then tried using syntax-quote within a Clojure function, but again, syntax-quote is resolving/namespace-qualifying the symbols, and of course, a function's arguments are always evaluated on the way in, which leads to tedious and unpleasant quoting of SUO-KIF symbols. I'd welcome any thoughts/pointers about how best to approach this. Don -- 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
tools.logging question
I would like to conditionally generate log statements based on run-time checks of various application-specific info. I note the following: Logging levels are specified by clojure keywords corresponding to the values used in log4j and commons-logging: :trace, :debug, :info, :warn, :error, :fatal log macro Usage: (log level message) … Evaluates and logs a message only if the specified level is enabled. So, it occurs to me that for the level argument to log, I could pass in a function that would figure out if I really wanted to log anything right then, or not. In the case that I *do* want to log something, that function would return the log level, e.g. :info (this part seems to work fine…) But what could my function return if it didn't want anything to be logged at this point? Any log level beneath the current level in effect would seem to work, but figuring that out feels hackish, and what if the lowest level of logging (:trace ?) is enabled, then what? Nil and/or false did not work at all in my test! Is there something like a :noop level, that would never be enabled, and could be returned by my function whenever it decided it did not want the log to happen? Obviously/alternately I could wrap all my logging in (when (log-decision args) (log :level message)) But right now I'd rather do all this with just the log call,and I'm hoping there is already a way to do what I ask above, or if not, willingness to add something like a :noop level Don -- 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
Re: No longer able to write a UUID to Postgres with ClojureQL
On Dec 6, 2011, at 11:23 AM, Sean Corfield wrote: On Tue, Dec 6, 2011 at 6:12 AM, Herwig Hochleitner hhochleit...@gmail.com wrote: 2011/12/6 Sean Corfield seancorfi...@gmail.com: So the question is probably: why is ClojureQL assuming all generated keys are integers? It shouldn't, and doesn't now: https://github.com/LauJensen/clojureql/commit/f7ffe88b166e6f60eccb3b4f46b7db5d69dbcc64 Thanks for tracing this and taking the time to post it. I have confirmed that this change/commit fixes my/the problem! Thank you Herwig for the fix, and thank you Sean for narrowing the problem down! -- 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
No longer able to write a UUID to Postgres with ClojureQL
For those of you following along at home, my spate of bad luck continues….
A week or so ago, I was happily writing and reading UUIDs into Postgres with
ClojureQL.
Then, all of a sudden, it stopped working, and I can't figure out why.
Shame on me for not being more careful about documenting when it worked, and
what changed.
And a lot of stuff changed in the interim…
So I wrote small example project to demonstrate the problem:
I have verified that I can write UUIDs into Postgres with java.jdbc itself, so
that is evidence that the issue is not with java.jdbc, the Postgres JDBC
library, nor my Postgres server.
(def u1 (. UUID (randomUUID)))
(def u2 (. UUID (randomUUID)))
(defn write-uuid-jdbc
[uid name]
(sql/with-connection postgres-db
(sql/insert-values
:testuuid
[:uid :name]
[uid name])))
(defn read-table-clojureql
[]
@(table postgres-db :testuuid))
(defn write-uuid-clojureql
[uid name]
(conj! (table postgres-db :testuuid)
{:uid uid :name name}))
This illustrates the problem:
(write-uuid-jdbc u1 jdbc)
works.
(write-uuid-clojureql u2 clojureql)
throws the following exception:
Bad value for type int : d812274a-a1ff-4ce5-962e-005f3c893459
[Thrown class org.postgresql.util.PSQLException]
Restarts:
0: [QUIT] Quit to the SLIME top level
Backtrace:
0:
org.postgresql.jdbc2.AbstractJdbc2ResultSet.toInt(AbstractJdbc2ResultSet.java:2759)
1:
org.postgresql.jdbc2.AbstractJdbc2ResultSet.getInt(AbstractJdbc2ResultSet.java:2003)
Now write u2 with jdbc:
(write-uuid-jdbc u2 jdbc)
And read the entire table back out using ClojureQL:
(read-table-clojureql)
({:name jdbc, :uid #UUID 2896de2b-2c48-40ab-83a6-cee6c2be16cd}
{:name jdbc, :uid #UUID d812274a-a1ff-4ce5-962e-005f3c893459})
So ClojureQL can certainly read the table, and return the UUIDs, but can't
write them…
Here is the relevant part of project.clj:
:dependencies [[org.clojure/clojure 1.2.1]
[postgresql/postgresql 9.1-901.jdbc4]
[org.clojure/java.jdbc 0.1.1]
[clojureql 1.1.0-SNAPSHOT]
])
I woud definitely appreciate/welcome any suggestions about why this is
happening, or how it might be fixed….
I've pushed this example test case/project up to GitHub in case anyone wants to
poke around:
dcj/postgres-uuid-test
Don
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Re: FYI: problem I had with namespace, defrecord, and import, or Hyphen characters in namespaces considered harmful
On Dec 2, 2011, at 1:29 PM, Phil Hagelberg wrote:
I was using defrecord for the first time, to create a type that I wanted to
throw+ via slingshot to signal errors from a library.
For what it's worth, the main point of slingshot is removing the
necessity of creating custom classes for exceptions, so this shouldn't
be necessary in the first place.
Would you elaborate on this a bit more? I would greatly appreciate the
education!
Let's say I am writing some code that uses three different libraries (actiona,
actionb, and actionc) to accomplish its goals.
Each of these action libraries can generate an exception that indicates that
things did not go well for the user/client.
I'd like to write my code so that the try+ clause is the everything works
path, and that I then catch various errors that each of my actions may have
generated.
Assume that I need to distinguish between the three possible action exceptions,
and handle them completely differently.
If each of the (independently written) action libraries throws its own map,
then how do I distinguish between these maps, especially if they happen to use
identical keywords to report errors?
One reason I was/am attracted to the each action library should define its own
error record type I mentioned originally is that it makes distinguishing
between these different exceptions trivial:
(try+
(- (actiona data)
(actionb)
(actionc))
(catch actiona-error ...)
(catch actionb-error ...)
(catch actionc-error …))
Perhaps putting multiple exception generating actions into one try+ is not the
recommended/idiomatic approach?
I guess I could be convinced of that, but at the moment, I really like
concentrating first on implementing the functionality of my app,
and then catching and dealing with all the errors at the top level.
I find code that for every call has to test or try/catch errors for every thing
it does is more painful to follow/read, but maybe that is just my
bias/limitation.
To take a random example, the library clj-http throws its normal response map
when the http response code it receives is not unexceptional-status?
So how do I catch that?
By looking for a key of :status?
That seems quite ripe for key name collisions, if there are more than one
action in the try block that could create an exception, and more than one
action generates a map with the keyword :status
Here is what I am doing right now:
(defn http-response-map?
[hrm]
(get hrm :status false))
(try+
(client/get url)
(catch http-response-map? {:keys [status headers body]} … ))
I had some confusion last night when I was not specific enough about the
exceptions I was catching,
and a catch of Object that I (in error) thought would only catch the last
remaining exception caught everything,
and something else that I didn't expect threw, and I didn't realize the problem
for a while….totally my fault,
but further motivation that catches be very specific about what they are
catching,
and I'd like to understand how best to do that without defining custom classes.
Best regards,
Don
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FYI: problem I had with namespace, defrecord, and import, or Hyphen characters in namespaces considered harmful
I was using defrecord for the first time, to create a type that I wanted to throw+ via slingshot to signal errors from a library. I'd seen an example of this in another library, and I pretty much just cut and pasted it into my project. I understood that I need to explicitly import the resulting class into clients that use my library, and attempted to do so. When loading the client library that uses and imports, I got this: foo-bar.core.foo-bar-error [Thrown class java.lang.ClassNotFoundException] Restarts: 0: [QUIT] Quit to the SLIME top level Backtrace: 0: java.net.URLClassLoader$1.run(URLClassLoader.java:202) 1: java.security.AccessController.doPrivileged(Native Method) 2: java.net.URLClassLoader.findClass(URLClassLoader.java:190) 3: clojure.lang.DynamicClassLoader.findClass(DynamicClassLoader.java:61) 4: java.lang.ClassLoader.loadClass(ClassLoader.java:306) 5: java.lang.ClassLoader.loadClass(ClassLoader.java:247) 6: java.lang.Class.forName0(Native Method) 7: java.lang.Class.forName(Class.java:169) 8: factmigrate.core$eval1645$loading__4414__auto1646.invoke(core.clj:1) 9: factmigrate.core$eval1645.invoke(core.clj:1) --more-- After a LOT of time and experimentation, I finally realized that in my import statement, I need to replace the hyphen character in my namespace (let's call my namespace foo-bar.core) to an underscore. So in a client of my library, it needs to do something like this (ns foobarclient.core (:use foo-bar.core) (:import foo_bar.core foo-bar-error)) Assuming that somewhere in the foo-bar.core namespace I had done something like this: (defrecord foo-bar-error [blah1 blah2]) I am still recovering from this debugging session, but my current thought is that this was all my fault, and I just need to be smarter about Java interop and naming issues. The hyphen/underscore issue is mentioned here: http://clojure.org/libs Lib Conventions Clojure defines conventions for naming and structuring libs: A lib name is a symbol that will typically contain two or more parts separated by periods. A lib's container is a Java resource whose classpath-relative path is derived from the lib name: The path is a string Periods in the lib name are replaced by slashes in the path Hyphens in the lib name are replaced by underscores in the path But I did not find this right away, and even after I did find it, it was not immediately obvious to me what the implication was in an import statement. So, I simply wanted to document this for the mailing list, in the hope of preventing others from stumbling into this, and maybe if they do, they will find this explanation in their searches… Don -- 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
Re: New to Clojure
On Jun 9, 2011, at 11:49 AM, Laurent PETIT wrote: I've seen people coming from a java background quite happy to start discovering clojure via the 4clojure website. Hey, I've got an idea: Maybe we could get the 4clojure folks to hook their site up to Twitter to let us know how people solve these puzzles… :-( Don -- 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
Re: Clojure ideas repository / todo list
On May 15, 2011, at 1:34 AM, Thorsten Wilms wrote: * Wrapper around git or darcs for using them as storage backends See: rnewman/clj-git - GitHub for a start on this. -- 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
Re: Clojure ideas repository / todo list
On May 14, 2011, at 2:17 PM, Islon Scherer wrote: Is there anyplace people post ideas of libraries/frameworks/functions that would be nice to be implemented in clojure? Sometimes I want to help the community but I don't know what to do (an idea), what's already done (yeah, I know one can search github or ask here but you can't be 100% sure it's not already implemented). Maybe a wiki or something like that would do the job. Here is one idea: At IO this week, Google announced their new API Discovery Service: It provides a lightweight, JSON-based API that exposes machine-readable metadata about Google APIs including: A directory of supported APIs. A machine-readable Discovery document for each of the supported APIs that includes: A list of API resource schemas based on JSON Schema A list of API methods and available parameters for each method. A list of available OAuth 2.0 scopes. Inline documentation of methods, parameters and available parameter values. http://code.google.com/apis/discovery/ https://code.google.com/apis/discovery/v1/using.html It would be great/cool to have a Clojure library that accessed the discovery service, and created Clojure libraries that implement the Google APIs described by this service. -- 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
Re: [ANN] emacs-nexus (Emacs client for Nexus Maven repository servers)
On Feb 14, 2011, at 8:21 PM, Michael Ossareh wrote: Along with anything that is listed in :repositories in your project.clj ? +1 -- 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
Re: Clojure 1.3: Integrating clj-stacktrace?
On Aug 24, 2010, at 9:55 PM, Phil Hagelberg wrote: Thoughts? +1. The existing stack traces are pretty horrible. Phil's proposal, or something similar, would be a huge improvement. -- 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
ANN: clj-facebook, a Clojure client library for Facebook apps
I'd like to announce the initial release of clj-facebook, a Facebook client library in Clojure. The code can be found here: http://github.com/rnewman/clj-facebook We welcome comments and proposed code improvements. Don -- 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 To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
ANN: clj-facebook, a Clojure client library for Facebook apps
I'd like to announce the initial release of clj-facebook, a Facebook client library in Clojure. The code can be found here: http://github.com/rnewman/clj-facebook We welcome comments and proposed code improvements. Don -- 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 To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words REMOVE ME as the subject.
