Re: [ANN] CloCoP - constraint programming for Clojure

[Dmitry Groshev]

Great stuff!

I'm wondering what's the "realworld" difference between JaCoP and CHOCO. 
Why did you choose the former?

On Tuesday, September 10, 2013 5:39:46 AM UTC+4, Alex Engelberg wrote:
>
> http://github.com/aengelberg/clocop
>
> CloCoP is a Clojure wrapper of the Java library JaCoP. The acronyms stand 
> for "Clojure/Java Constraint Programming". This invites comparison to the 
> core.logic library, and you may wonder why we need both. There are a few 
> ways in which, in my opinion, the JaCoP system is better than core.logic:
>
>- JaCoP is more "plug-in-able," with an extensive set of 
>customizations to the way that the search operates. There are interfaces 
>for different components of the search, and each has several 
>implementations. 
>- I found that with core.logic, I was somewhat limited by the set of 
>available constraints. JaCoP has many different constraints that seem to 
>more suit my needs for solving challenging problems. 
>- As the core.logic people 
> say,JaCoP is 
> anywhere from 10X-100X faster than core.logic at solving Finite 
>Domain problems.
>
> JaCoP has a lot of "global constraints" which are very powerful and 
> essential for describing certain problems. As Radoslaw Szymanek (an 
> author of JaCoP) says, "CP without global constraints is just [a] plain 
> academic toy. Using problems with arithmetic constraints is doing CP bad 
> publicity."
>
> If you'd like to see implementations of sample problems in CloCoP, check 
> out the test 
> cases
>  (https://github.com/aengelberg/clocop/tree/master/test/clocop).
>

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Re: Clojure, floats, ints and OpenGL

[Mikera]

On Friday, 13 September 2013 12:11:50 UTC+8, tbc++ wrote:

> >> If we can do away with the interface generation, then support for 
> arbitrary primitive arguments should become relatively straightforward.
>
> How would we even call a function without an interface? Remember 
> everything is defined behind vars, so you simply can't assume that a 
> function won't be re-defed without notice. This is the reason interfaces 
> exist notice how the following works:
>
> user=> (defn foo ^long [^long x] x)
> #'user/foo
> user=> (defn baz [x] (foo x))
> #'user/baz
> user=> (baz 42)
> 42
> user=> (defn foo ^double [^double x] x)
> #'user/foo
> user=> (baz 42)
>
> ClassCastException user$foo cannot be cast to clojure.lang.IFn$LL 
>  user/baz (NO_SOURCE_FILE:1)
> user=>
>

Good example to discuss!

I agree there is a subtle tradeoff between performance and dynamism here.

Any interface dispatch via a var uses an extra level of indirection (in the 
dynamic var case, this includes a thread-local check for any bindings) and 
already adds some overhead. If you are happy using Clojure's dynamic 
features to pass arbitrary (boxed / Object) arguments and redefine vars on 
the fly like that, you probably don't really care about optimal performance 
very much anyway and a standard IFn invoke should be OK. 

For performance-sensitive code, you ideally want primitive-typed code to be 
compiled to a direct method call (invokevirtual) and not go via any var 
lookup / interface invoke at all. This would mean you would also need to 
redefine/recompile baz if you wanted to use a changed version of foo, but 
that's a relatively minor inconvenience IMHO. If you redefine baz after 
redefining foo (e.g. by reloading the whole namespace), then everything 
will still work. I'm not sure if it is possible to get this precise 
behaviour in Clojure at present - but it would certainly be great for high 
performance code.

If we want *both* maximum performance and dynamic flexibility, then I think 
we need a completely different approach. Clojure vars as currently designed 
won't cut it. Probably something like an on-demand re-compilation strategy 
based on a var dependency graph would be needed. I personally think that's 
the right long-term direction, but that's definitely Clojure 2.0 territory.
 

>
> Do a prototype with definterface/genclass or something and then report 
> your results. My suspicions are that you'll find doing this without 
> interfaces, while maintaining Clojure's semantics, is impossible.
>

You may be right. Though it also probably depends on what you consider 
documented (promised not to change in public API) vs. undocumented 
(implementation detail) semantics. Some of the subtleties on what happens 
to existing code when you redefine vars are arguably in the latter 
category. Observe:

(defn foo ^double [^double x] (inc x))
(defn baz [x] (foo x))
(baz 42)
=> 43.0
(ns-unmap *ns* 'foo)
(defn foo ^double [^double x] (dec x))
(baz 42)
=> 43.0

i.e. it's fairly easy to trick Clojure into keeping an old version of a var 
around. Does that count as officially documented behaviour we are obliged 
to maintain?

Either way, if Clojure's semantics prove to be a fundamental issue for 
performance, then I think it is better to start work to improve Clojure's 
semantics (perhaps targeting 2.0 if we think it's a really big breaking 
change). This would be better, IMHO, than forever accepting semantics that 
prevent idiomatic code from ever being truly fast. I'd rather see a bit of 
breakage and fix my code when upgrading to Clojure 2.0 than be stuck with 
poor performance forever.

 

>
> Timothy
>
>
> On Thu, Sep 12, 2013 at 8:41 PM, Mikera 
> > wrote:
>
>> People *have* run into this problem a lot. People have just worked around 
>> it. The existence of great libraries like HipHip and vectorz-clj and some 
>> of Zach's stuff is IMHO to a large extent because people have needed high 
>> performance operations (often involving primitives / primitive arrays / 
>> custom JVM types) and have found it easier to implement these in a new 
>> library than wait for the support to appear in Clojure itself.
>>
>> So we have lots of great, performance-oriented libraries. Cool. 
>>
>> But not having comprehensive JVM primitive support is still a big problem 
>> for Clojure. It means that:
>> a) We'll get lots of ecosystem fragmentation as people with slightly 
>> different requirements implement their own solutions in slightly 
>> different/incompatible ways. We're seeing this already. Lisp Curse etc.
>> b) People with very strong performance requirements on the JVM (e.g. 
>> OpenGL, big data numerics, scientific computing, heavy duty websites) are 
>> more likely to avoid Clojure and do their work in Scala / Java instead. The 
>> community will lose exactly the people who have both the motivation and 
>> skills to fix these kind of issues.
>> c) We won't get the wider reputation for performance that I think Clojure 
>> deserves and should asp

clojure.java.jdbc connection pool example

[Josh Kamau]

Hello there ;

I am in desparate need of a clojure.jdbc with a connection pool example.

I have googled and the link to github example is broken.

Please help.

Thanks.
Josh

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Re: clojure.java.jdbc connection pool example

[Shantanu Kumar]

Hi Josh,

On Friday, 13 September 2013 15:52:47 UTC+5:30, Josh Kamau wrote:
>
> Hello there ;
>
> I am in desparate need of a clojure.jdbc with a connection pool example. 
>

You can see an example here that uses Apache DBCP (please excuse the plug):
https://github.com/kumarshantanu/clj-dbcp

There are C3P0 and BoneCP connection pool libraries too:
https://github.com/opiskelijarekisteri-devel/clj-bonecp
http://stackoverflow.com/questions/11571433/what-is-the-proper-way-to-store-a-global-connection-in-clojure

Shantanu

>

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Re: clojure.java.jdbc connection pool example

[Josh Kamau]

Thanks alot.

Let me check them out.

Josh


On Fri, Sep 13, 2013 at 1:41 PM, Shantanu Kumar wrote:

> Hi Josh,
>
>
> On Friday, 13 September 2013 15:52:47 UTC+5:30, Josh Kamau wrote:
>>
>> Hello there ;
>>
>> I am in desparate need of a clojure.jdbc with a connection pool example.
>>
>
> You can see an example here that uses Apache DBCP (please excuse the plug):
> https://github.com/kumarshantanu/clj-dbcp
>
> There are C3P0 and BoneCP connection pool libraries too:
> https://github.com/opiskelijarekisteri-devel/clj-bonecp
>
> http://stackoverflow.com/questions/11571433/what-is-the-proper-way-to-store-a-global-connection-in-clojure
>
> Shantanu
>
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Re: Different behaviour when using (def ^:macro ...) outside top-level

[André Gustavo Rigon]

Yeah, it's the difference in behaviour that I don't understand.

Thanks for the workaround though Gunnar.

On Friday, September 13, 2013 2:35:37 AM UTC-3, Cedric Greevey wrote:
>
> On Fri, Sep 13, 2013 at 1:08 AM, Gunnar Völkel 
> 
> > wrote:
>
>> `def` does not handle `:macro true` metadata on the provided symbol.
>>
>  
> Umm ... according to the OP, it worked perfectly when the def was a 
> top-level form, just not when it was nested in an if. If your claim were 
> correct the OP would have had no joy with either my-defn1 *or* my-defn2, 
> rather than only the latter not working.
>
>

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reference types (var, atom, ref, agent) and add-watch: deterministic order of notification

[gixxi]

Hi,

i got a question on reference type instances with attached watches.

Consider a reference type instance R with a watch W attached by (add-watch 
R :watcher #(...)) and

a n parallel activities committing a transition to R in some monotonic 
order 0..n-1.

Does Clojure ensure that the function calls by the watch dog are executed 
in the very same order? Is it possible to wrap the watch dog notification 
in a synchronisation block?

Thanks in advance

Best regards

Christian

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Re: clojure.java.jdbc connection pool example

[gixxi]

Hi Josh,

I would opt for using Tomcat 7 Pool API - 
http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html

The following code wraps the pool api and provides reading a config file

(ns foo
  (:require [clojure.java.io :as io])
  (:import [java.io PushbackReader])
  (:gen-class))

(defn conf [file]
  "Reads a config file containing the connection params (url, driver)"
  (binding [*read-eval* false]
(with-open [r (io/reader file)]
  (read (PushbackReader. r)

(defn datasource [file]
  "creates a pooled data source"
  (let
[config (conf file) ds (new org.apache.tomcat.jdbc.pool.DataSource) pp 
(new org.apache.tomcat.jdbc.pool.PoolProperties)]
(do
  (.setDriverClassName pp (:classname config))
  (.setUrl pp (:subname config))
  (.setUsername pp (:user config))
  (.setPassword pp (:password config))
  (.setTestOnBorrow pp true)
  (.setValidationQuery pp "SELECT 1")
  (.setMaxActive pp 5)
  (.setInitialSize pp 1)
  (.setMaxWait pp 1)
  (.setPoolProperties ds pp)
  (identity ds

create a file dbconnection.ini with you jdbc connection params as per the 
following example (uses derby in-memory db)

{
:classname "org.apache.derby.jdbc.EmbeddedDriver"
:subprotocol "memory"
:subname "jdbc:derby:memory:myDB;create=true"
:user ""
:password ""
}

now you can load the config and create a pooled connection as wished

(def ds (datasource (clojure.java.io/as-file "db.properties")))

you can obtain a connection using

{:datasource ds}


Cheers
Christian

Am Freitag, 13. September 2013 12:22:47 UTC+2 schrieb Josh Kamau:
>
> Hello there ;
>
> I am in desparate need of a clojure.jdbc with a connection pool example. 
>
> I have googled and the link to github example is broken.
>
> Please help.
>
> Thanks.
> Josh
>

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Re: clojure.java.jdbc connection pool example

[Josh Kamau]

Thanks.

I have used C3P0 for now... I will look at tomcat7 pool though

Josh


On Fri, Sep 13, 2013 at 3:19 PM, gixxi <
christian.meichs...@informatik.tu-chemnitz.de> wrote:

> Hi Josh,
>
> I would opt for using Tomcat 7 Pool API -
> http://tomcat.apache.org/tomcat-7.0-doc/jdbc-pool.html
>
> The following code wraps the pool api and provides reading a config file
>
> (ns foo
>   (:require [clojure.java.io :as io])
>   (:import [java.io PushbackReader])
>   (:gen-class))
>
> (defn conf [file]
>   "Reads a config file containing the connection params (url, driver)"
>   (binding [*read-eval* false]
> (with-open [r (io/reader file)]
>   (read (PushbackReader. r)
>
> (defn datasource [file]
>   "creates a pooled data source"
>   (let
> [config (conf file) ds (new org.apache.tomcat.jdbc.pool.DataSource) pp
> (new org.apache.tomcat.jdbc.pool.PoolProperties)]
> (do
>   (.setDriverClassName pp (:classname config))
>   (.setUrl pp (:subname config))
>   (.setUsername pp (:user config))
>   (.setPassword pp (:password config))
>   (.setTestOnBorrow pp true)
>   (.setValidationQuery pp "SELECT 1")
>   (.setMaxActive pp 5)
>   (.setInitialSize pp 1)
>   (.setMaxWait pp 1)
>   (.setPoolProperties ds pp)
>   (identity ds
>
> create a file dbconnection.ini with you jdbc connection params as per the
> following example (uses derby in-memory db)
>
> {
> :classname "org.apache.derby.jdbc.EmbeddedDriver"
> :subprotocol "memory"
> :subname "jdbc:derby:memory:myDB;create=true"
> :user ""
> :password ""
> }
>
> now you can load the config and create a pooled connection as wished
>
> (def ds (datasource (clojure.java.io/as-file "db.properties")))
>
> you can obtain a connection using
>
> {:datasource ds}
>
>
> Cheers
> Christian
>
> Am Freitag, 13. September 2013 12:22:47 UTC+2 schrieb Josh Kamau:
>
>> Hello there ;
>>
>> I am in desparate need of a clojure.jdbc with a connection pool example.
>>
>> I have googled and the link to github example is broken.
>>
>> Please help.
>>
>> Thanks.
>> Josh
>>
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Re: reference types (var, atom, ref, agent) and add-watch: deterministic order of notification

[Jay Fields]

Watch behavior varies a bit by ref type, I believe. You'll probably
want to look into the details of the specific ref type you're using.

for atoms and refs, I believe the watch is done on the thread that's
updating the ref. Since retries can occur you can't really count on
ordering. You could create your own thread to single thread the action
- I've done that in the past with success. While you can't rely on
ordering, having the old and new value to diff might be enough to know
what actions you want to perform in your watch (on your single thread)

for agents, I believe everything will be single threaded and in the
order of agent updates.

On Fri, Sep 13, 2013 at 8:04 AM, gixxi
 wrote:
> Hi,
>
> i got a question on reference type instances with attached watches.
>
> Consider a reference type instance R with a watch W attached by (add-watch R
> :watcher #(...)) and
>
> a n parallel activities committing a transition to R in some monotonic order
> 0..n-1.
>
> Does Clojure ensure that the function calls by the watch dog are executed in
> the very same order? Is it possible to wrap the watch dog notification in a
> synchronisation block?
>
> Thanks in advance
>
> Best regards
>
> Christian
>
> --
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Re: Why is clojure so powerful?

[John Hyaduck]

Have you made the free version available yet?  I would like to read it and 
review.  John Hyaduck

On Wednesday, September 4, 2013 5:32:01 PM UTC-4, Tomislav Tomšić wrote:
>
> I suspect, there are numerous possible ways to answer that question. One 
> can ignore it, others would care to offer superficial, "no it isn't", but I 
> guess, few would answer, it is because clojure is the member of the Lisp 
> family of programming languages. Which immediately invites predictable 
> question.
>
>
> Why is Lisp so powerful?
>
> I guesstimate, there are three possible responses on that question. One is 
> to ignore it, second one is to take it as encouragement for further 
> inquiry, and the third one is to say something along the following lines: 
> “It is because of the lists, dummy. Lisp is built on lists.”
>
>
> Very well then, why are lists so powerful?
>
>
> Yes, there is answer(s), but as I hope we all know, every answer opens the 
> door for new questions and problems. In other words, we have an, hopefully 
> clear and self-understandable, answer to why is Lisp so powerful, but we 
> are now facing numerous, previously unimaginable choices and opportunities 
> to improve Lisp further, which is the reason why I am putting this message 
> here, in the group dedicated to the new and continually improving member of 
> Lisp programming family.
>
>
> I hope to solve and clarify as many as I can, but it demands time and 
> other resources, which is why I decided to put answer(s) and reasons for 
> them in a book. It is called “Arrogance of Abstraction”, and it is 
> available through Amazon. Amazon allows, even encourages authors, to put an 
> effort to contact audience. In other words, it will be available for free 
> download from Amazon at following days this month: 2013-09-08 and 
> 2013-09-13. I haven't decided yet at what other days will be available for 
> download. If you have an advice, feel free to put it here.
>
>
> Thank you for your patience
>
> Tomislav Tomsic
>

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Maximize Fantasy Baseball Lineup

[Mark Watson]

Hey, newish user here.

I want to make an app that finds the optimal lineup for fantasy baseball 
games.

Each player is assigned a cost, the average points they earn a game, and 
position. For example: Andrew McCutchen, 3.4, 4900, OF

You have to pick one catcher, one pitcher, one first basemen, one second 
basemen, one shortstop, one third basemen, and three outfielders. The catch 
is you also have to stay below a predetermined total cost of your team. I 
want to maximize my total average points while staying under the cost limit.

My plan was to iterate through every possible combo, and swap an atom if I 
find a lineup with a better total average points while staying under the 
total cost limit.

My issues are:

1) This seems like an inelegant solution (brute force)

2) I don't know of a good way to handle the fact that I need to choose 
three outfielders, but can't choose any one outfielder multiple times

Any advice? Thanks!

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Fantasy Baseball Lineup Optimization

[Mark Watson]

Hi, newish user here.

I want to make an app that finds a simple, optimized, fantasy baseball 
lineup.

Each player has a cost associated with them, as well as the average points 
per game they score, and position. For example: Mike Napoli, 4600, 2.9, 1B

You have to choose one of each position: catcher, pitcher, 1st base, 2nd 
base, 3rd base, and shortstop. You also have to pick three outfielders. It 
would be easy to just pick the players with the highest points per game, 
but you also need to stay under a specified total cost.

Currently, I iterate through every possibility, and swap an atom with a new 
lineup if the total average points is higher, while staying under the total 
cost limit.

My issues are:

1) This seems like an inelegant solution (brute force)
2) I don't know how to best handle the fact that I need to select three 
outfielders from a single list, and cannot select one player more than once

Any advice, suggestions would be great. Thanks!

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Re: Clojure, floats, ints and OpenGL

[James Reeves]

On 13 September 2013 08:54, Mikera  wrote:

> Either way, if Clojure's semantics prove to be a fundamental issue for
> performance, then I think it is better to start work to improve Clojure's
> semantics (perhaps targeting 2.0 if we think it's a really big breaking
> change). This would be better, IMHO, than forever accepting semantics that
> prevent idiomatic code from ever being truly fast. I'd rather see a bit of
> breakage and fix my code when upgrading to Clojure 2.0 than be stuck with
> poor performance forever.
>

Out of curiosity, what is the performance hit in these cases?

Floats obviously save memory, and I believe they're also between 15% to 40%
more efficient for division, at least on Intel CPUs. Is there also a cost
to be paid passing doubles to OpenGL? Do you know what that cost is?

- James

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bug with '#_' macro as last line?

[m_albert137]

Greetings!

First, thanks in advance to anyone looking at this,
and to the good folks that made clojure possible.

Tinkering, I find that if I redirect input so that clojure.main reads
from a file, and the last line is a form that has been commented out
with "#_", then I get an error message.

Explicitly, if I try a file like this (the stuff between the '' lines):

(println "Hello, world.")
#_ (println "Hello, world")


and I then try "java -cp '[path]' clojure.main < filename.clj", then the 
first
println succeeds, but I then get an error message:

"RuntimeException EOF while reading  clojure.lang.Util.runtimeException 
(Util.java:219).

I'm using clojure 1.5.1 with java 1.7.0_25 on Windows 8 (and cygwin).

Thank you.

Sincerely,
 Mike Albert

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Re: clojure.java.jdbc connection pool example

[Sean Corfield]

There are examples in the documentations for both c3p0 and BoneCP:

http://clojure-doc.org/articles/ecosystem/java_jdbc/connection_pooling.html

Note: this is the home for the "official" java.jdbc documentation so
that it can be augmented by the community, rather than locked in the
java.jdbc repo where only folks with a signed CA can submit
enhancements...

Sean

On Fri, Sep 13, 2013 at 3:22 AM, Josh Kamau  wrote:
> Hello there ;
>
> I am in desparate need of a clojure.jdbc with a connection pool example.
>
> I have googled and the link to github example is broken.
>
> Please help.
>
> Thanks.
> Josh
>
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-- 
Sean A Corfield -- (904) 302-SEAN
An Architect's View -- http://corfield.org/
World Singles, LLC. -- http://worldsingles.com/

"Perfection is the enemy of the good."
-- Gustave Flaubert, French realist novelist (1821-1880)

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Re: [ANN] CloCoP - constraint programming for Clojure

[Alex Engelberg]

To Daniel's comment: that's a great idea (I'm sorta new to this whole 
releasing-a-library thing so I didn't think of that), and I'll definitely 
make a branch for that if I think of a big idea that I want to implement 
that involves breaking changes. But I figure that if someone other than me 
thinks of something like that, we'll probably discuss it a bit and figure 
something out (rather than just showing up with a pull request).

To Dmitry's comment: I've actually never tried Choco, I essentially chose 
JaCoP because it occured first in my "Java Constraint Programming" google 
search. Now I'm seeing that a lot of constraint programmers use Choco, and 
I'll try it out. I will point out that JaCoP walked away with some bronze 
and silver medals (with Gecode getting ALL the golds) at the FlatZinc 
challenge. (Choco didn't compete at all, though.)

On Friday, September 13, 2013 12:32:31 AM UTC-7, Dmitry Groshev wrote:
>
> Great stuff!
>
> I'm wondering what's the "realworld" difference between JaCoP and CHOCO. 
> Why did you choose the former?
>
> On Tuesday, September 10, 2013 5:39:46 AM UTC+4, Alex Engelberg wrote:
>>
>> http://github.com/aengelberg/clocop
>>
>> CloCoP is a Clojure wrapper of the Java library JaCoP. The acronyms stand 
>> for "Clojure/Java Constraint Programming". This invites comparison to the 
>> core.logic library, and you may wonder why we need both. There are a few 
>> ways in which, in my opinion, the JaCoP system is better than core.logic:
>>
>>- JaCoP is more "plug-in-able," with an extensive set of 
>>customizations to the way that the search operates. There are interfaces 
>>for different components of the search, and each has several 
>>implementations. 
>>- I found that with core.logic, I was somewhat limited by the set of 
>>available constraints. JaCoP has many different constraints that seem to 
>>more suit my needs for solving challenging problems. 
>>- As the core.logic people 
>> say,JaCoP is 
>> anywhere from 10X-100X faster than core.logic at solving Finite 
>>Domain problems.
>>
>> JaCoP has a lot of "global constraints" which are very powerful and 
>> essential for describing certain problems. As Radoslaw Szymanek (an 
>> author of JaCoP) says, "CP without global constraints is just [a] plain 
>> academic toy. Using problems with arithmetic constraints is doing CP bad 
>> publicity."
>>
>> If you'd like to see implementations of sample problems in CloCoP, check 
>> out the test 
>> cases
>>  (https://github.com/aengelberg/clocop/tree/master/test/clocop).
>>
>

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Re: Why is clojure so powerful?

[Mark C]

I see "Arrogance of Abstraction" can be borrowed free (today only I think) 
by Kindle users with Amazon prime.

On Friday, September 13, 2013 10:36:14 AM UTC-4, John Hyaduck wrote:
>
> Have you made the free version available yet?  I would like to read it and 
> review.  John Hyaduck
>
> On Wednesday, September 4, 2013 5:32:01 PM UTC-4, Tomislav Tomšić wrote:
>>
>> I suspect, there are numerous possible ways to answer that question. One 
>> can ignore it, others would care to offer superficial, "no it isn't", but I 
>> guess, few would answer, it is because clojure is the member of the Lisp 
>> family of programming languages. Which immediately invites predictable 
>> question.
>>
>>
>> Why is Lisp so powerful?
>>
>> I guesstimate, there are three possible responses on that question. One 
>> is to ignore it, second one is to take it as encouragement for further 
>> inquiry, and the third one is to say something along the following lines: 
>> “It is because of the lists, dummy. Lisp is built on lists.”
>>
>>
>> Very well then, why are lists so powerful?
>>
>>
>> Yes, there is answer(s), but as I hope we all know, every answer opens 
>> the door for new questions and problems. In other words, we have an, 
>> hopefully clear and self-understandable, answer to why is Lisp so powerful, 
>> but we are now facing numerous, previously unimaginable choices and 
>> opportunities to improve Lisp further, which is the reason why I am putting 
>> this message here, in the group dedicated to the new and continually 
>> improving member of Lisp programming family.
>>
>>
>> I hope to solve and clarify as many as I can, but it demands time and 
>> other resources, which is why I decided to put answer(s) and reasons for 
>> them in a book. It is called “Arrogance of Abstraction”, and it is 
>> available through Amazon. Amazon allows, even encourages authors, to put an 
>> effort to contact audience. In other words, it will be available for free 
>> download from Amazon at following days this month: 2013-09-08 and 
>> 2013-09-13. I haven't decided yet at what other days will be available for 
>> download. If you have an advice, feel free to put it here.
>>
>>
>> Thank you for your patience
>>
>> Tomislav Tomsic
>>
>

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Re: Clojure, floats, ints and OpenGL

[Timothy Baldridge]

>> This would be better, IMHO, than forever accepting semantics that
prevent idiomatic code from ever being truly fast.

You're going to have a hard time convincing people to give up some of
the dynamism of Clojure just for the sake of more performance. Especially
considering that many Clojure users are perfectly okay with boxed values,
let alone need floats or other primitives.

But what you are describing creates a whole ton of new problems, problems I
don't see a good solution for. What you are describing would require the
recompilation of entire source trees when a inner function is modified. So
now we're in the Scala/Java land of recompile after every edit. Perhaps
there's a use-case for invoke dynamic here, but now you're talking about
breaking backwards compatibility for everyone not using Java 7+.

I'll be the first to admit that I'd like to rewrite the Clojure compiler as
a true multi-pass optimizing compiler. But that's a task I haven't
undertaken for two reasons 1) it's a ton of work that would take months (if
not years) to reach the level of performance currently offered by Clojure.
2) I really don't need it. Every time I need that level of performance I
drop to Java, CUDA or some other high performance toolkit.

Personally I think it would be much better for someone to come up with a
typed lisp that interops very cleanly with Clojure. That way you can build
your inner kernels using a lisp-like language, and then glue it together
with Clojure.

But let me close by saying, if you really want better primitives, I'd
suggest writing up a proposal for how it would work, perhaps even with some
example using macros and genclass. Until then we don't have anything to go
off of, people say "I'd love to have feature X", well we all would, but all
the suggestions thus far won't work, so how do you plan on fixing that?

Timothy


On Fri, Sep 13, 2013 at 1:54 AM, Mikera wrote:

> On Friday, 13 September 2013 12:11:50 UTC+8, tbc++ wrote:
>
>> >> If we can do away with the interface generation, then support for
>> arbitrary primitive arguments should become relatively straightforward.
>>
>> How would we even call a function without an interface? Remember
>> everything is defined behind vars, so you simply can't assume that a
>> function won't be re-defed without notice. This is the reason interfaces
>> exist notice how the following works:
>>
>> user=> (defn foo ^long [^long x] x)
>> #'user/foo
>> user=> (defn baz [x] (foo x))
>> #'user/baz
>> user=> (baz 42)
>> 42
>> user=> (defn foo ^double [^double x] x)
>> #'user/foo
>> user=> (baz 42)
>>
>> ClassCastException user$foo cannot be cast to clojure.lang.IFn$LL
>>  user/baz (NO_SOURCE_FILE:1)
>> user=>
>>
>
> Good example to discuss!
>
> I agree there is a subtle tradeoff between performance and dynamism here.
>
> Any interface dispatch via a var uses an extra level of indirection (in
> the dynamic var case, this includes a thread-local check for any bindings)
> and already adds some overhead. If you are happy using Clojure's dynamic
> features to pass arbitrary (boxed / Object) arguments and redefine vars on
> the fly like that, you probably don't really care about optimal performance
> very much anyway and a standard IFn invoke should be OK.
>
> For performance-sensitive code, you ideally want primitive-typed code to
> be compiled to a direct method call (invokevirtual) and not go via any var
> lookup / interface invoke at all. This would mean you would also need to
> redefine/recompile baz if you wanted to use a changed version of foo, but
> that's a relatively minor inconvenience IMHO. If you redefine baz after
> redefining foo (e.g. by reloading the whole namespace), then everything
> will still work. I'm not sure if it is possible to get this precise
> behaviour in Clojure at present - but it would certainly be great for high
> performance code.
>
> If we want *both* maximum performance and dynamic flexibility, then I
> think we need a completely different approach. Clojure vars as currently
> designed won't cut it. Probably something like an on-demand re-compilation
> strategy based on a var dependency graph would be needed. I personally
> think that's the right long-term direction, but that's definitely Clojure
> 2.0 territory.
>
>
>>
>> Do a prototype with definterface/genclass or something and then report
>> your results. My suspicions are that you'll find doing this without
>> interfaces, while maintaining Clojure's semantics, is impossible.
>>
>
> You may be right. Though it also probably depends on what you consider
> documented (promised not to change in public API) vs. undocumented
> (implementation detail) semantics. Some of the subtleties on what happens
> to existing code when you redefine vars are arguably in the latter
> category. Observe:
>
> (defn foo ^double [^double x] (inc x))
> (defn baz [x] (foo x))
> (baz 42)
> => 43.0
> (ns-unmap *ns* 'foo)
> (defn foo ^double [^double x] (dec x))
> (baz 42)
> => 43.0
>
> i.e. it's fairly easy to tr

clojure web framework

[Jon Barker]

anybody know the easiest way to create web applications and deploy to 
amazon web services?  (either EC2 or elastic beanstalk)

Thanks,
Jon

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Re: [ANN] quickie- autotest plugin for clojure.test

[Christopher Allen]

Link:

https://github.com/jakepearson/quickie

Is it possible to see *some* of the stack trace so you can debug?

Also you should include a screenshot of what the library looks like in 
action. :)


On Friday, September 13, 2013 10:57:35 AM UTC-7, Jake Pearson wrote:
>
> Hi,
> Quickie is a leiningen plugin to autotest clojure.test tests.  There don't 
> seem to be any active projects for clojure.test, so a couple of people at 
> my office wrote one.  Please let me know if you have any problems or ideas:
>
>- Uses the builtin clojure.test test runner so you don't need to 
>rewrite your tests
>- Tools.namespace will unload and reload namespaces as needed to keep 
>process in sync
>- Runs every time a clojure file in your project changes
>- Uses (Clansi)[https://github.com/ams-clj/clansi] to show a red or 
>green bar to know if you tests are passing
>- Filters out exception stacktraces to remove cruft
>
> thanks,
> Jake
>

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[ANN] quickie- autotest plugin for clojure.test

[Jake Pearson]

Hi,
Quickie is a leiningen plugin to autotest clojure.test tests.  There don't 
seem to be any active projects for clojure.test, so a couple of people at 
my office wrote one.  Please let me know if you have any problems or ideas:

   - Uses the builtin clojure.test test runner so you don't need to rewrite 
   your tests
   - Tools.namespace will unload and reload namespaces as needed to keep 
   process in sync
   - Runs every time a clojure file in your project changes
   - Uses (Clansi)[https://github.com/ams-clj/clansi] to show a red or 
   green bar to know if you tests are passing
   - Filters out exception stacktraces to remove cruft

thanks,
Jake

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Re: [ANN] quickie- autotest plugin for clojure.test

[Jake Pearson]

Hi,
I added a screenshot to the readme.  I think in general filtering items 
from the stacktrace is a good idea, but I am probably doing it too much.  I 
have an idea.  I will work on it this weekend.

thanks,
Jake

On Friday, September 13, 2013 12:21:00 PM UTC-6, Christopher Allen wrote:
>
> Link:
>
> https://github.com/jakepearson/quickie
>
> Is it possible to see *some* of the stack trace so you can debug?
>
> Also you should include a screenshot of what the library looks like in 
> action. :)
>
>
> On Friday, September 13, 2013 10:57:35 AM UTC-7, Jake Pearson wrote:
>>
>> Hi,
>> Quickie is a leiningen plugin to autotest clojure.test tests.  There 
>> don't seem to be any active projects for clojure.test, so a couple of 
>> people at my office wrote one.  Please let me know if you have any problems 
>> or ideas:
>>
>>- Uses the builtin clojure.test test runner so you don't need to 
>>rewrite your tests
>>- Tools.namespace will unload and reload namespaces as needed to keep 
>>process in sync
>>- Runs every time a clojure file in your project changes
>>- Uses (Clansi)[https://github.com/ams-clj/clansi] to show a red or 
>>green bar to know if you tests are passing
>>- Filters out exception stacktraces to remove cruft
>>
>> thanks,
>> Jake
>>
>

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Re: clojure web framework

[Christopher Allen]

Well for creation itself, http://www.luminusweb.net/ represents best 
practices with Ring, Compojure, and the usual attendant libraries.

For deployment, I'd say something like Fabric or Ansible is going to be the 
simplest way to start.

On Friday, September 13, 2013 10:45:10 AM UTC-7, Jon Barker wrote:
>
> anybody know the easiest way to create web applications and deploy to 
> amazon web services?  (either EC2 or elastic beanstalk)
>
> Thanks,
> Jon
>

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[ANN] LispCast Introduction to Clojure Videos

[Eric Normand]

Hi all!

I announced the Kickstarter project here way back in February and got a 
good response. I thought you might want to know that the videos are 
available for sale.

http://videos.lispcast.com

The target audience is people who are very new to Lisp. It begins with 
opening and closing parens :) and ends with data-driven programming. The 
point is to show how powerful programming with data can be.

At the moment, I am selling them for $12 with no DRM. The price may 
increase soon on advice from several people.

Enjoy!
Eric

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How does "

[larry google groups]

I am stupid and recursion is clearly beyond my intellect. Martin Trojer has 
a great blog post here which I learned a lot from but I don't understand 
why the final example works:

http://martintrojer.github.io/clojure/2013/07/17/non-tailrecursive-functions-in-coreasync/

He offers this as an example of recursively walking a binary search tree:

(defn walk [tree ch]
  (letfn [(walker [t]
(go
 (when t
   (walker (:left t))
   (>! ch (:value t))
   (walker (:right t)]
(go
 (! ch (:value t))
   (http://groups.google.com/group/clojure?hl=en
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Re: [ANN] clojuretip.herokuapp.com

[Ruslan Prokopchuk]

I've created new app with the same name using github source. Thanks a lot, 
Steven!

On Thursday, September 12, 2013 9:44:18 PM UTC+3, Ruslan Prokopchuk wrote:
>
> Oh, where this awesomeness has been lost today? Heroku replies: 
> *No such app*
> On Saturday, September 7, 2013 8:09:06 PM UTC+3, Steven Degutis wrote:
>>
>> Yesterday in #clojure:
>>
>>  To get your random API learnin' of the day, just run: (->> 
>> clojure.core quote the-ns ns-publics seq rand-nth val meta ((juxt :name 
>> :doc)) (map println) dorun)
>>
>> Awesome, right? So I put a lil web wrapper around it and uploaded it to 
>> clojuretip.herokuapp.com and https://github.com/sdegutis/clojuretip.
>>
>> -Steven
>>
>

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Re: [ANN] quickie- autotest plugin for clojure.test

[Alexandr Kurilin]

Thanks for putting this plugin together, very useful!

A couple of remarks:

   - Seems to the advantage over aphyr/prism in terms of not forcing you to
   use the foo-test convention, for those of us who are keeping same names as
   the namespaces in the test/ folder. It's possible I'm being non-idiomatic
   here and I should suffix tests with -test instead.
   - Looks like it's not running under the test leiningen profile. In my
   case, I suppress a lot of logging in test mode to keep lein test output
   readable, and quickie bypasses that. I'm not sure if perhaps I'm just not
   logging things the right way and this is a wontfix.
   - Would be very neat if it re-ran only the tests that changed, or whose
   corresponding namespace contents changed.

Thanks!


On Fri, Sep 13, 2013 at 12:36 PM, Jake Pearson wrote:

> Hi,
> I added a screenshot to the readme.  I think in general filtering items
> from the stacktrace is a good idea, but I am probably doing it too much.  I
> have an idea.  I will work on it this weekend.
>
> thanks,
> Jake
>
>
> On Friday, September 13, 2013 12:21:00 PM UTC-6, Christopher Allen wrote:
>>
>> Link:
>>
>> https://github.com/**jakepearson/quickie
>>
>> Is it possible to see *some* of the stack trace so you can debug?
>>
>> Also you should include a screenshot of what the library looks like in
>> action. :)
>>
>>
>> On Friday, September 13, 2013 10:57:35 AM UTC-7, Jake Pearson wrote:
>>>
>>> Hi,
>>> Quickie is a leiningen plugin to autotest clojure.test tests.  There
>>> don't seem to be any active projects for clojure.test, so a couple of
>>> people at my office wrote one.  Please let me know if you have any problems
>>> or ideas:
>>>
>>>- Uses the builtin clojure.test test runner so you don't need to
>>>rewrite your tests
>>>- Tools.namespace will unload and reload namespaces as needed to
>>>keep process in sync
>>>- Runs every time a clojure file in your project changes
>>>- Uses 
>>> (Clansi)[https://github.com/**ams-clj/clansi]
>>>to show a red or green bar to know if you tests are passing
>>>- Filters out exception stacktraces to remove cruft
>>>
>>> thanks,
>>> Jake
>>>
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-- 
Alexandr Kurilin - Front Row Education (www.frontrowed.com)
206.687.8740 | a...@kurilin.net
@alex_kurilin

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Re: Maximize Fantasy Baseball Lineup

[Norman Richards]

This sounds like a classic knapsack problem.  For such a small problem
space, a simple dynamic programming solution would suffice.


If you are interested in exploring this problem at a larger scale, I high
recommend coursera's Discrete Optimization class:

https://class.coursera.org/optimization-001

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Re: clojure web framework

[Anton Podviaznikov]

Hi John,

It's super easy to deploy Clojure web app (ring) to Amazon Beanstalk. I 
think there were few blog posts about that.

Basically you just need https://github.com/weavejester/lein-beanstalk

Anton

On Friday, September 13, 2013 2:45:10 PM UTC-3, Jon Barker wrote:
>
> anybody know the easiest way to create web applications and deploy to 
> amazon web services?  (either EC2 or elastic beanstalk)
>
> Thanks,
> Jon
>

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clojure.java.jdbc connection pool example

[Daniel]

I believe Korma uses c3p0 for connection pooling right out of the box.

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Re: How does "

[Cedric Greevey]

It forces the go block to wait until (walker (:left t)) pushes something --
that is, for the recursively-entered go block to complete. Similarly the
right branch is waited for before the parent go block completes. So forcing
an in-order traversal of the tree.


On Fri, Sep 13, 2013 at 5:13 PM, larry google groups <
lawrencecloj...@gmail.com> wrote:

>
> I am stupid and recursion is clearly beyond my intellect. Martin Trojer
> has a great blog post here which I learned a lot from but I don't
> understand why the final example works:
>
>
> http://martintrojer.github.io/clojure/2013/07/17/non-tailrecursive-functions-in-coreasync/
>
> He offers this as an example of recursively walking a binary search tree:
>
> (defn walk [tree ch]
>   (letfn [(walker [t]
> (go
>  (when t
>(walker (:left t))
>(>! ch (:value t))
>(walker (:right t)]
> (go
>  (  (close! ch
>
> and then he writes:
>
> "This looks promising, but the results in the channel can be in any order 
> (since there are no order guarantees in the scheduling of go processes) – 
> this also means that some of the values might be missing since the “top” go 
> process can be scheduled before a child one. We need a little bit more 
> synchronisation to arrive at a working solution."
>
>
> and then offers this as the final working example:
>
> (defn walk [tree ch]
>   (letfn [(walker [t]
> (go
>  (when t
>((>! ch (:value t))
>( (go
>  (  (close! ch
>
> I am confused what this line does:
>
>(
> It looks like we are pulling a value off channel that's returned from that 
> call to walker? But why? We seem to be throwing this value away? I don't see 
> it being stored anywhere.
>
> How does this give us synchronization?
>
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