Re: Performance of defmulti in both ClojureScript and Clojure

[Andy-]

Looks like they're pretty slow compared to a simple case:

http://jsperf.com/cljs-multimethods

https://github.com/rauhs/cljs-perf


On Saturday, April 25, 2015 at 10:33:18 AM UTC-4, Timur wrote:
>
> Hi everyone,
>
> There are situations where I want to dispatch functions using based on 
> their certain properties. I can also use case statements instead but it 
> looks more coupled and more change is required if I want to add new types. 
>
> What I want to ask is if I need to avoid using multi-methods for 
> performance reasons? I read somewhere that they are not really fast but the 
> posts were old and the performance might have been improved in between. 
> Should I favor case and cond branches instead of defmulti when I need 
> performance? 
>
> Thanks for your help!!!
>
> Regards.
>
> Timur
>

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Re: Performance of defmulti in both ClojureScript and Clojure

[David Nolen]

A quick glance at your benchmarking setup, it's not clear that you are
benchmarking what you think you are benchmarking, and jsperf is not a
suitable benchmarking harness (irrespective of it's popularity).
Benchmarking is hard, benchmarking JavaScript is harder, and benchmarking
JavaScript that went through Google Closure is even more challenging than
that. It's for this reason we have our own simple benchmarking suite that
we run in the project repo itself against 4 JavaScript engines (V8,
JavaScriptCore, SpiderMonkey, Nashorn) at the command line.

For people that want to see accurate benchmarking information posted to
some public location, this is a great place to get involved contributing to
ClojureScript without needing to dig into the compiler.

My earlier points about the general performance expectations of
multimethods in ClojureScript still stands :)

David

On Mon, Apr 27, 2015 at 9:44 AM, Andy-  wrote:

> Looks like they're pretty slow compared to a simple case:
>
> http://jsperf.com/cljs-multimethods
>
> https://github.com/rauhs/cljs-perf
>
>
> On Saturday, April 25, 2015 at 10:33:18 AM UTC-4, Timur wrote:
>>
>> Hi everyone,
>>
>> There are situations where I want to dispatch functions using based on
>> their certain properties. I can also use case statements instead but it
>> looks more coupled and more change is required if I want to add new types.
>>
>> What I want to ask is if I need to avoid using multi-methods for
>> performance reasons? I read somewhere that they are not really fast but the
>> posts were old and the performance might have been improved in between.
>> Should I favor case and cond branches instead of defmulti when I need
>> performance?
>>
>> Thanks for your help!!!
>>
>> Regards.
>>
>> Timur
>>
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Re: Performance of defmulti in both ClojureScript and Clojure

[Andy-]

You're right. I didn't check it enough. I did check out the source (and 
btw, was very impressed with the result) but it looks like the function 
call ended up doing nothing. I just put in a side effect and I got the 
following results:

"[a :one], (multi-test), 100 runs, 2933 msecs"
"[a :one], (fn-test), 100 runs, 500 msecs"

Much more reasonable and I'm willing to pay for that for using multimethods.

I removed the jsperf and updated the repo. Sorry for spreading FUD.

Cheers

On Monday, April 27, 2015 at 10:07:07 AM UTC-4, David Nolen wrote:
>
> A quick glance at your benchmarking setup, it's not clear that you are 
> benchmarking what you think you are benchmarking, and jsperf is not a 
> suitable benchmarking harness (irrespective of it's popularity). 
> Benchmarking is hard, benchmarking JavaScript is harder, and benchmarking 
> JavaScript that went through Google Closure is even more challenging than 
> that. It's for this reason we have our own simple benchmarking suite that 
> we run in the project repo itself against 4 JavaScript engines (V8, 
> JavaScriptCore, SpiderMonkey, Nashorn) at the command line.
>
> For people that want to see accurate benchmarking information posted to 
> some public location, this is a great place to get involved contributing to 
> ClojureScript without needing to dig into the compiler.
>
> My earlier points about the general performance expectations of 
> multimethods in ClojureScript still stands :)
>
> David
>
> On Mon, Apr 27, 2015 at 9:44 AM, Andy- > 
> wrote:
>
>> Looks like they're pretty slow compared to a simple case:
>>
>> http://jsperf.com/cljs-multimethods
>>
>> https://github.com/rauhs/cljs-perf
>>
>>
>> On Saturday, April 25, 2015 at 10:33:18 AM UTC-4, Timur wrote:
>>>
>>> Hi everyone,
>>>
>>> There are situations where I want to dispatch functions using based on 
>>> their certain properties. I can also use case statements instead but it 
>>> looks more coupled and more change is required if I want to add new types. 
>>>
>>> What I want to ask is if I need to avoid using multi-methods for 
>>> performance reasons? I read somewhere that they are not really fast but the 
>>> posts were old and the performance might have been improved in between. 
>>> Should I favor case and cond branches instead of defmulti when I need 
>>> performance? 
>>>
>>> Thanks for your help!!!
>>>
>>> Regards.
>>>
>>> Timur
>>>
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>
>

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Re: Performance of defmulti in both ClojureScript and Clojure

[Phillip Lord]

I think that the answer is, it depends, and, there might be some
surprises in store.

In my own use, I found multimethods collapse in performance as a result
of changes to the interface hierarchy in the library I was using (my
tests cases went from 45s to over 4mins).

I circumvented this by fiddling with the dispatch function, so that it
returned ONLY classes that exactly matched one of the ones in the
multi-method, and memoizing the look up of these classes. In effect,
this closes down the multi-method, so it can no longer be freely
extended. This dropped the time of my test cases dramatically.

How widely applicable these results are, I do not know, as I never got
down to the mechanistics underneath. Still, my conclusion is, you might
want to test things out first!

My full set of experiments are here...

http://www.russet.org.uk/blog/3007


Timur  writes:

> Hi everyone,
>
> There are situations where I want to dispatch functions using based on 
> their certain properties. I can also use case statements instead but it 
> looks more coupled and more change is required if I want to add new types. 
>
> What I want to ask is if I need to avoid using multi-methods for 
> performance reasons? I read somewhere that they are not really fast but the 
> posts were old and the performance might have been improved in between. 
> Should I favor case and cond branches instead of defmulti when I need 
> performance? 
>
> Thanks for your help!!!

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Re: Performance of defmulti in both ClojureScript and Clojure

[Alex Miller]

Sounds like you might have been running into the absence of multimethod 
caching for the default case (http://dev.clojure.org/jira/browse/CLJ-1429), 
which has been fixed in 1.7. 

Just on a side note, that repo does not change the default lein :jvm-opts, 
which are bad for benchmarking. I recommend at least:

  :jvm-opts ^:replace ["-server"]

Criterium now yells at you if you haven't done this. 


On Monday, April 27, 2015 at 9:43:11 AM UTC-5, Phillip Lord wrote:
>
>
> I think that the answer is, it depends, and, there might be some 
> surprises in store. 
>
> In my own use, I found multimethods collapse in performance as a result 
> of changes to the interface hierarchy in the library I was using (my 
> tests cases went from 45s to over 4mins). 
>
> I circumvented this by fiddling with the dispatch function, so that it 
> returned ONLY classes that exactly matched one of the ones in the 
> multi-method, and memoizing the look up of these classes. In effect, 
> this closes down the multi-method, so it can no longer be freely 
> extended. This dropped the time of my test cases dramatically. 
>
> How widely applicable these results are, I do not know, as I never got 
> down to the mechanistics underneath. Still, my conclusion is, you might 
> want to test things out first! 
>
> My full set of experiments are here... 
>
> http://www.russet.org.uk/blog/3007 
> 
>  
>
>
> Timur > writes: 
>
> > Hi everyone, 
> > 
> > There are situations where I want to dispatch functions using based on 
> > their certain properties. I can also use case statements instead but it 
> > looks more coupled and more change is required if I want to add new 
> types. 
> > 
> > What I want to ask is if I need to avoid using multi-methods for 
> > performance reasons? I read somewhere that they are not really fast but 
> the 
> > posts were old and the performance might have been improved in between. 
> > Should I favor case and cond branches instead of defmulti when I need 
> > performance? 
> > 
> > Thanks for your help!!! 
>

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Re: complex numbers in clojure

[endbegin]

I have been thinking along the lines of mikera and Maik - and it seems like 
there is no further progress here? I would like to take a crack at creating 
a complex number type, but implemented as a library to Clojure. I am not 
sure where to start, and if anyone here has suggestions, I'd be happy to 
hear them. 

A complex number could simply be a vector of two elements, or a map with 
:real and :imag keys (or something lightweight) - and I am not sure what it 
would require to make this type work happily with code arithmetic functions 
in Clojure and Java Math. 

It would also have to work with seq operations in Clojure - for instance: 
If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2 
c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2 
5). 

I am having trouble figuring out all the pieces that need to be 
implemented. Is it even possible to implement this as a library, or does 
this need to be a part of clojure.core?

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Re: Performance of defmulti in both ClojureScript and Clojure

[Phillip Lord]

Alex Miller  writes:
> Sounds like you might have been running into the absence of multimethod 
> caching for the default case (http://dev.clojure.org/jira/browse/CLJ-1429), 
> which has been fixed in 1.7. 

No, I don't think; my default case was and is "throw an exception".


> Just on a side note, that repo does not change the default lein :jvm-opts, 
> which are bad for benchmarking. I recommend at least:
>
>   :jvm-opts ^:replace ["-server"]
>
> Criterium now yells at you if you haven't done this. 


I know. My use case, though, involves using Clojure through the REPL, so
I tested in that way, since this is how it runs in lein.

Phil

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with-redefs does not work for macros

[Vebjorn Ljosa]

In one of my tests, I was trying to mock something 
(`clojure.tools.logging/warn`) that happened to be a macro. It had me 
puzzled for a while until I discovered that `with-redefs` resets the value 
of the vars after the body is executed, but does not reset the flag that 
says that the var is a macro:

$ lein repl
Clojure 1.6.0
…
user=> (defmacro foo [] `(prn "I am a macro")) 
#'user/foo 
user=> (clojure.test/function? 'foo)
false
user=> (with-redefs [foo (fn [] 42)])
nil
user=> (clojure.test/function? foo) 
true
user=> (foo) 
ArityException Wrong number of args (0) passed to: user/foo 
clojure.lang.AFn.throwArity (AFn.java:429) 
user=> (foo 42 42) 
(clojure.core/prn "I am a macro")

Is this a bug?

I looked at the source for `with-redefs-fn`, and the fix appears simple: 
record for each val whether it's a macro or not, and then call the 
`(setMacro)` method on the vars that should be macros after resetting their 
values.

Vebjorn

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Re: complex numbers in clojure

[Andy Fingerhut]

Unless the Java Math library handles complex types already, I don't know of
any way to extend it in a way that would let you get the answer you want
from (Math/abs my-complex-number) in Clojure.

If you want code that gives the correct answers, a library using vectors or
maps for complex numbers can get you there.  Memory footprint and
performance should be better with Clojure records or a new class written
directly in Java.  With a library, I don't know of any way to be able to
mix Clojure's arithmetic operations like + - * / etc. with its existing
numeric types, and your new library-implemented complex types.

Support of Clojure's arithmetic operations on complex numbers might only be
achievable by modifying Clojure itself.  Depending upon your goals, the
down side of that approach is that it will not become part of the normal
Clojure distribution unless the Clojure core team wants that addition,
which I would guess would be very low on their priority list (just a guess
-- I have no inside knowledge there).

Andy

On Mon, Apr 27, 2015 at 8:39 AM, endbegin  wrote:

> I have been thinking along the lines of mikera and Maik - and it seems
> like there is no further progress here? I would like to take a crack at
> creating a complex number type, but implemented as a library to Clojure. I
> am not sure where to start, and if anyone here has suggestions, I'd be
> happy to hear them.
>
> A complex number could simply be a vector of two elements, or a map with
> :real and :imag keys (or something lightweight) - and I am not sure what it
> would require to make this type work happily with code arithmetic functions
> in Clojure and Java Math.
>
> It would also have to work with seq operations in Clojure - for instance:
> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2
> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2
> 5).
>
> I am having trouble figuring out all the pieces that need to be
> implemented. Is it even possible to implement this as a library, or does
> this need to be a part of clojure.core?
>
> --
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Re: complex numbers in clojure

[Gary Verhaegen]

As far as I understand, your example with Math/abs would need to be part of
Java.

You cannot extend the arithmetic operators in Java, and you will not be
able to extend static Java methods like Math/abs.

What you may be able to do is make your custom type play nice with Clojure
operators, like Clojure's rationals and bignums.

I'd suggest looking at the code for these, and considering a Java class
with two primitive attributes rather than a Clojure vector or map (which
have a big overhead compared to a simple number). Depending on what you
want to do, you may also want to consider implementing a "vector of
complex" type, which could be a single object with two primitive arrays.

If you're targeting a performant implementation, you should probably cross
post to numerical-clojure; people over there have a lot of experience about
numerical optimizations in Clojure.

On Monday, 27 April 2015, endbegin  wrote:

> I have been thinking along the lines of mikera and Maik - and it seems
> like there is no further progress here? I would like to take a crack at
> creating a complex number type, but implemented as a library to Clojure. I
> am not sure where to start, and if anyone here has suggestions, I'd be
> happy to hear them.
>
> A complex number could simply be a vector of two elements, or a map with
> :real and :imag keys (or something lightweight) - and I am not sure what it
> would require to make this type work happily with code arithmetic functions
> in Clojure and Java Math.
>
> It would also have to work with seq operations in Clojure - for instance:
> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2
> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2
> 5).
>
> I am having trouble figuring out all the pieces that need to be
> implemented. Is it even possible to implement this as a library, or does
> this need to be a part of clojure.core?
>
> --
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Re: Performance of defmulti in both ClojureScript and Clojure

[Alex Miller]

I fleshed out some of this a bit more in a blog post with perf numbers in 
case anyone's interested:

http://insideclojure.org/2015/04/27/poly-perf/


On Saturday, April 25, 2015 at 9:39:06 PM UTC-5, Alex Miller wrote:
>
> On Saturday, April 25, 2015 at 9:33:18 AM UTC-5, Timur wrote:
>>
>> Hi everyone,
>>
>> There are situations where I want to dispatch functions using based on 
>> their certain properties. I can also use case statements instead but it 
>> looks more coupled and more change is required if I want to add new types. 
>>
>
> case is useful for the particular situation where you have a finite set of 
> compile-time constants that you are looking for (integers, characters, 
> etc). Then case will leverage a special JVM bytecode that performs a 
> *constant-time* look-up (not linear-time like checking a series of cond 
> conditions, etc). This is one of the two bytecode options (tableswitch, 
> rather than lookupswitch) underlying the Java switch/case feature.
>
> What I want to ask is if I need to avoid using multi-methods for 
>> performance reasons? I read somewhere that they are not really fast but the 
>> posts were old and the performance might have been improved in between. 
>> Should I favor case and cond branches instead of defmulti when I need 
>> performance? 
>>
>
> multimethods are slower than protocols - they must effectively invoke the 
> dispatch function, perform a linear search for a match across the cases, 
> and then invoke the actual implementation function. Protocols leverage JVM 
> internals to select the right implementation, then invoke it. However, the 
> search part of multimethods is cached, making that step fast after the 
> initial call. The last time I benchmarked multimethods with class dispatch 
> vs protocols on Java 1.8 + Clojure 1.7 alphas (can't remember which one), I 
> found multimethods were about 5x slower.
>
> If you want fastest type-based dispatch with open extension, then 
> protocols are the best.
> If you want any other type of dispatch with open extension, then 
> multimethods are the best.
> If you want a closed system of constant choices, then case is best 
> (constant-time lookup!)
> If you want a closed system of arbitrary conditions, then cond is best.
>
> I have never compared the performance of cond vs multimethods for 
> something like this. My guess is that multimethods are faster as they 
> evaluate a single condition, then do a table lookup once cached vs 
> evaluating a series of conditions every time. 
>
> Alex 
>
>

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Re: complex numbers in clojure

[endbegin]

This is what I suspected. Of course, this is not just for abs, but really 
for any mathematical operation. Sqrt, Trig operations etc.

I will study the Ratio type more closely, but note that something like 
(Math/abs (/ 22 7)) does not work. 


On Monday, April 27, 2015 at 12:45:32 PM UTC-4, Gary Verhaegen wrote:
>
> As far as I understand, your example with Math/abs would need to be part 
> of Java.
>
> You cannot extend the arithmetic operators in Java, and you will not be 
> able to extend static Java methods like Math/abs.
>
> What you may be able to do is make your custom type play nice with Clojure 
> operators, like Clojure's rationals and bignums.
>
> I'd suggest looking at the code for these, and considering a Java class 
> with two primitive attributes rather than a Clojure vector or map (which 
> have a big overhead compared to a simple number). Depending on what you 
> want to do, you may also want to consider implementing a "vector of 
> complex" type, which could be a single object with two primitive arrays.
>
> If you're targeting a performant implementation, you should probably cross 
> post to numerical-clojure; people over there have a lot of experience about 
> numerical optimizations in Clojure.
>
> On Monday, 27 April 2015, endbegin > 
> wrote:
>
>> I have been thinking along the lines of mikera and Maik - and it seems 
>> like there is no further progress here? I would like to take a crack at 
>> creating a complex number type, but implemented as a library to Clojure. I 
>> am not sure where to start, and if anyone here has suggestions, I'd be 
>> happy to hear them. 
>>
>> A complex number could simply be a vector of two elements, or a map with 
>> :real and :imag keys (or something lightweight) - and I am not sure what it 
>> would require to make this type work happily with code arithmetic functions 
>> in Clojure and Java Math. 
>>
>> It would also have to work with seq operations in Clojure - for instance: 
>> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2 
>> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2 
>> 5). 
>>
>> I am having trouble figuring out all the pieces that need to be 
>> implemented. Is it even possible to implement this as a library, or does 
>> this need to be a part of clojure.core?
>>
>> -- 
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Re: complex numbers in clojure

[endbegin]

As far as I know, Java Math does not have a complex number type. Some 
implementations of a complex number exist (such as Apache Commons Math), 
but they create a Complex class that implements Serializeable and a Commons 
specific interface.  

Modifying clojure.core itself is a bit daunting, and like you said, it 
would need to be a priority for the core team.



On Monday, April 27, 2015 at 12:45:46 PM UTC-4, Andy Fingerhut wrote:
>
> Unless the Java Math library handles complex types already, I don't know 
> of any way to extend it in a way that would let you get the answer you want 
> from (Math/abs my-complex-number) in Clojure.
>
> If you want code that gives the correct answers, a library using vectors 
> or maps for complex numbers can get you there.  Memory footprint and 
> performance should be better with Clojure records or a new class written 
> directly in Java.  With a library, I don't know of any way to be able to 
> mix Clojure's arithmetic operations like + - * / etc. with its existing 
> numeric types, and your new library-implemented complex types.
>
> Support of Clojure's arithmetic operations on complex numbers might only 
> be achievable by modifying Clojure itself.  Depending upon your goals, the 
> down side of that approach is that it will not become part of the normal 
> Clojure distribution unless the Clojure core team wants that addition, 
> which I would guess would be very low on their priority list (just a guess 
> -- I have no inside knowledge there).
>
> Andy
>
> On Mon, Apr 27, 2015 at 8:39 AM, endbegin 
> > wrote:
>
>> I have been thinking along the lines of mikera and Maik - and it seems 
>> like there is no further progress here? I would like to take a crack at 
>> creating a complex number type, but implemented as a library to Clojure. I 
>> am not sure where to start, and if anyone here has suggestions, I'd be 
>> happy to hear them. 
>>
>> A complex number could simply be a vector of two elements, or a map with 
>> :real and :imag keys (or something lightweight) - and I am not sure what it 
>> would require to make this type work happily with code arithmetic functions 
>> in Clojure and Java Math. 
>>
>> It would also have to work with seq operations in Clojure - for instance: 
>> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2 
>> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2 
>> 5). 
>>
>> I am having trouble figuring out all the pieces that need to be 
>> implemented. Is it even possible to implement this as a library, or does 
>> this need to be a part of clojure.core?
>>
>> -- 
>> 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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>
>

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Re: complex numbers in clojure

[Andy Fingerhut]

People frequently make their own modified versions of Clojure without
having their changes made part of the core Clojure distribution.  That is
why I said "depending upon your goals".  If your goal is to try it out and
learn from it, and you don't care whether it becomes part of the standard
Clojure distribution, then it does not matter what the Clojure core team's
priorities are, because they are not involved.

Andy

On Mon, Apr 27, 2015 at 10:46 AM, endbegin  wrote:

> As far as I know, Java Math does not have a complex number type. Some
> implementations of a complex number exist (such as Apache Commons Math),
> but they create a Complex class that implements Serializeable and a Commons
> specific interface.
>
> Modifying clojure.core itself is a bit daunting, and like you said, it
> would need to be a priority for the core team.
>
>
>
> On Monday, April 27, 2015 at 12:45:46 PM UTC-4, Andy Fingerhut wrote:
>>
>> Unless the Java Math library handles complex types already, I don't know
>> of any way to extend it in a way that would let you get the answer you want
>> from (Math/abs my-complex-number) in Clojure.
>>
>> If you want code that gives the correct answers, a library using vectors
>> or maps for complex numbers can get you there.  Memory footprint and
>> performance should be better with Clojure records or a new class written
>> directly in Java.  With a library, I don't know of any way to be able to
>> mix Clojure's arithmetic operations like + - * / etc. with its existing
>> numeric types, and your new library-implemented complex types.
>>
>> Support of Clojure's arithmetic operations on complex numbers might only
>> be achievable by modifying Clojure itself.  Depending upon your goals, the
>> down side of that approach is that it will not become part of the normal
>> Clojure distribution unless the Clojure core team wants that addition,
>> which I would guess would be very low on their priority list (just a guess
>> -- I have no inside knowledge there).
>>
>> Andy
>>
>> On Mon, Apr 27, 2015 at 8:39 AM, endbegin  wrote:
>>
>>> I have been thinking along the lines of mikera and Maik - and it seems
>>> like there is no further progress here? I would like to take a crack at
>>> creating a complex number type, but implemented as a library to Clojure. I
>>> am not sure where to start, and if anyone here has suggestions, I'd be
>>> happy to hear them.
>>>
>>> A complex number could simply be a vector of two elements, or a map with
>>> :real and :imag keys (or something lightweight) - and I am not sure what it
>>> would require to make this type work happily with code arithmetic functions
>>> in Clojure and Java Math.
>>>
>>> It would also have to work with seq operations in Clojure - for
>>> instance:
>>> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2
>>> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2
>>> 5).
>>>
>>> I am having trouble figuring out all the pieces that need to be
>>> implemented. Is it even possible to implement this as a library, or does
>>> this need to be a part of clojure.core?
>>>
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "Clojure" group.
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>>> your first post.
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>>
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Re: with-redefs does not work for macros

[Vebjorn Ljosa]

On Monday, April 27, 2015 at 12:34:14 PM UTC-4, Vebjorn Ljosa wrote:
>
> In one of my tests, I was trying to mock something 
> (`clojure.tools.logging/warn`) that happened to be a macro. It had me 
> puzzled for a while until I discovered that `with-redefs` resets the value 
> of the vars after the body is executed, but does not reset the flag that 
> says that the var is a macro:
>

Granted, using `with-redefs` with a macro rarely makes sense because 
macroexpansion has to occur within the extent of `with-redefs` for the 
redefinition to have any effect. (I can't even think of an example where I 
would want to do that, so maybe `with-redefs` should emit a warning when 
it's being asked to redefine a macro.) But in any case, an attempt to use 
`with-redefs` on something that happens to be a macro should not mess up 
the root binding permanently.

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Re: [ANN] Clojure Applied: From Practice to Practitioner

[Alex Miller]

The second beta of "Clojure Applied" is now available. This version adds 
Chapter 8 (Clojure Testing) as well as a foreword by Russ Olsen, and fixes 
for many of the reported errata.

https://pragprog.com/book/vmclojeco/clojure-applied

If you've already bought the book, you should get an email to download the 
new version.

Alex


On Monday, April 13, 2015 at 12:00:58 PM UTC-5, Alex Miller wrote:
>
> On Monday, April 13, 2015 at 9:40:39 AM UTC-5, Jonathon McKitrick wrote:
>>
>> Will we be notified as new content is added so we can update our 
>> electronic versions?
>>
>
> Yes, you should be notified when it's updated. Also, if you visit the 
> Pragmatic web site and log in, they will notify you if any books on your 
> bookshelf have been updated.
>
> We will probably have another update next week with chapter 8 and any 
> errata fixes since the first release.
>
> Alex
>  
>

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Re: complex numbers in clojure

[Lee Spector]

Just cheerleading: I, for one, would love for Clojure to have complex number 
support, however it can be arranged (built-in or through a library). 

I sometimes do quantum computing work and this issue has prevented progress on 
a couple of projects. I haven't tried to solve the problem myself, and I'm not 
sure exactly what the difficulties are in detail, but a couple of strong 
students have worked on this for me and been stymied.

I started my quantum computing work in Common Lisp, where complex numbers are 
free and easy... and it's frustrating that this (and only this) has prevented 
us from continuing that work now that we've switched to Clojure for almost 
everything else.

 -Lee



> On Apr 27, 2015, at 1:52 PM, Andy Fingerhut  wrote:
> 
> People frequently make their own modified versions of Clojure without having 
> their changes made part of the core Clojure distribution.  That is why I said 
> "depending upon your goals".  If your goal is to try it out and learn from 
> it, and you don't care whether it becomes part of the standard Clojure 
> distribution, then it does not matter what the Clojure core team's priorities 
> are, because they are not involved.
> 
> Andy
> 
> On Mon, Apr 27, 2015 at 10:46 AM, endbegin  > wrote:
> As far as I know, Java Math does not have a complex number type. Some 
> implementations of a complex number exist (such as Apache Commons Math), but 
> they create a Complex class that implements Serializeable and a Commons 
> specific interface.  
> 
> Modifying clojure.core itself is a bit daunting, and like you said, it would 
> need to be a priority for the core team.
> 
> 
> 
> On Monday, April 27, 2015 at 12:45:46 PM UTC-4, Andy Fingerhut wrote:
> Unless the Java Math library handles complex types already, I don't know of 
> any way to extend it in a way that would let you get the answer you want from 
> (Math/abs my-complex-number) in Clojure.
> 
> If you want code that gives the correct answers, a library using vectors or 
> maps for complex numbers can get you there.  Memory footprint and performance 
> should be better with Clojure records or a new class written directly in 
> Java.  With a library, I don't know of any way to be able to mix Clojure's 
> arithmetic operations like + - * / etc. with its existing numeric types, and 
> your new library-implemented complex types.
> 
> Support of Clojure's arithmetic operations on complex numbers might only be 
> achievable by modifying Clojure itself.  Depending upon your goals, the down 
> side of that approach is that it will not become part of the normal Clojure 
> distribution unless the Clojure core team wants that addition, which I would 
> guess would be very low on their priority list (just a guess -- I have no 
> inside knowledge there).
> 
> Andy
> 
> On Mon, Apr 27, 2015 at 8:39 AM, endbegin > wrote:
> I have been thinking along the lines of mikera and Maik - and it seems like 
> there is no further progress here? I would like to take a crack at creating a 
> complex number type, but implemented as a library to Clojure. I am not sure 
> where to start, and if anyone here has suggestions, I'd be happy to hear 
> them. 
> 
> A complex number could simply be a vector of two elements, or a map with 
> :real and :imag keys (or something lightweight) - and I am not sure what it 
> would require to make this type work happily with code arithmetic functions 
> in Clojure and Java Math. 
> 
> It would also have to work with seq operations in Clojure - for instance: 
> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2 c], 
> it would be nice to have the call 'map #(Math/abs %) v' produce (1 2 5). 
> 
> I am having trouble figuring out all the pieces that need to be implemented. 
> Is it even possible to implement this as a library, or does this need to be a 
> part of clojure.core?
> 
> -- 
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> Groups "Clojure" group.
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> first post.
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> 
> 
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> firs

Re: complex numbers in clojure

[Alex Miller]

I think it's unlikely that Clojure would add a complex number type. 
However, it might be possible to open up the system enough that new types 
could be created and integrated by others. I think this discussion and 
implementation from clojure-dev (about unsigned numbers) is pertinent:

https://groups.google.com/d/msg/clojure-dev/QF8P7_DK0rc/p8JOlF3Zs44J

In my last posts on that thread, I suggested some of the design and testing 
work that I would expect Rich to ask about. I did not get the impression 
that anyone cared enough to contribute further. If there was enough 
interest, I'd be happy to ask Rich about it.

Alex


On Monday, April 27, 2015 at 1:46:48 PM UTC-5, Lee wrote:
>
> Just cheerleading: I, for one, would love for Clojure to have complex 
> number support, however it can be arranged (built-in or through a library). 
>
> I sometimes do quantum computing work and this issue has prevented 
> progress on a couple of projects. I haven't tried to solve the problem 
> myself, and I'm not sure exactly what the difficulties are in detail, but a 
> couple of strong students have worked on this for me and been stymied.
>
> I started my quantum computing work in Common Lisp, where complex numbers 
> are free and easy... and it's frustrating that this (and only this) has 
> prevented us from continuing that work now that we've switched to Clojure 
> for almost everything else.
>
>  -Lee
>
>
>
> On Apr 27, 2015, at 1:52 PM, Andy Fingerhut  > wrote:
>
> People frequently make their own modified versions of Clojure without 
> having their changes made part of the core Clojure distribution.  That is 
> why I said "depending upon your goals".  If your goal is to try it out and 
> learn from it, and you don't care whether it becomes part of the standard 
> Clojure distribution, then it does not matter what the Clojure core team's 
> priorities are, because they are not involved.
>
> Andy
>
> On Mon, Apr 27, 2015 at 10:46 AM, endbegin  > wrote:
>
>> As far as I know, Java Math does not have a complex number type. Some 
>> implementations of a complex number exist (such as Apache Commons Math), 
>> but they create a Complex class that implements Serializeable and a Commons 
>> specific interface.  
>>
>> Modifying clojure.core itself is a bit daunting, and like you said, it 
>> would need to be a priority for the core team.
>>
>>
>>
>> On Monday, April 27, 2015 at 12:45:46 PM UTC-4, Andy Fingerhut wrote:
>>>
>>> Unless the Java Math library handles complex types already, I don't know 
>>> of any way to extend it in a way that would let you get the answer you want 
>>> from (Math/abs my-complex-number) in Clojure.
>>>
>>> If you want code that gives the correct answers, a library using vectors 
>>> or maps for complex numbers can get you there.  Memory footprint and 
>>> performance should be better with Clojure records or a new class written 
>>> directly in Java.  With a library, I don't know of any way to be able to 
>>> mix Clojure's arithmetic operations like + - * / etc. with its existing 
>>> numeric types, and your new library-implemented complex types.
>>>
>>> Support of Clojure's arithmetic operations on complex numbers might only 
>>> be achievable by modifying Clojure itself.  Depending upon your goals, the 
>>> down side of that approach is that it will not become part of the normal 
>>> Clojure distribution unless the Clojure core team wants that addition, 
>>> which I would guess would be very low on their priority list (just a guess 
>>> -- I have no inside knowledge there).
>>>
>>> Andy
>>>
>>> On Mon, Apr 27, 2015 at 8:39 AM, endbegin  wrote:
>>>
 I have been thinking along the lines of mikera and Maik - and it seems 
 like there is no further progress here? I would like to take a crack at 
 creating a complex number type, but implemented as a library to Clojure. I 
 am not sure where to start, and if anyone here has suggestions, I'd be 
 happy to hear them. 

 A complex number could simply be a vector of two elements, or a map 
 with :real and :imag keys (or something lightweight) - and I am not sure 
 what it would require to make this type work happily with code arithmetic 
 functions in Clojure and Java Math. 

 It would also have to work with seq operations in Clojure - for 
 instance: 
 If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 
 -2 c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 
 2 
 5). 

 I am having trouble figuring out all the pieces that need to be 
 implemented. Is it even possible to implement this as a library, or does 
 this need to be a part of clojure.core?

 -- 
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 Groups "Clojure" group.
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 Note that posts from new members are moderated - please be patient with 
 your first post.
 To uns

Crazy Need: Embed JavaScript Structure in Clojure

[JPatrick Davenport]

Hello,
So just to get it out: I do not want to evaluate the JavaScript, simply 
preserve it.

I'm working on an ArangoDB driver. Part of the wonder that is ArangoDB is 
its ability to support transactions. This is done using JSON. Part of the 
REST object for a transaction is what I want to do in the transaction. This 
is encapsulated in the "action" attribute of the posted JSON object. 

Here's an example
{...JSON configuration
 action: "function (){many lines of stuff here",
 More JSON configuration}

Now the way that this works in node is by converting the function into a 
String. I didn't know that String(function () {..valid JavaScript...}) 
would kick out a string version of the function. Pretty neat.

I want to do the same thing with Clojure. I presently take a map with one 
of the attributes of :action. I want something like this.
{:some-key :some-value,
 :action  (js-macro function(){
  console.log("pretty crappy transaction");
  console.log("another line");
})}

On the other side of the macro I want to get "function() {\t\t\t\n 
console.log(\"pretty crappy transaction\";\n\t\t\tconsole.log(\"another 
line\");\n} or there about.

I've got

(defmacro js [& js-fun]

(let [body (str js-fun)]

(subs body 1 (- (count body) 1

That gets the idea. Unfortunately, I loose the ";" as well as the new lines.

I'm pretty sure I don't *need* this macro. I can probably get away with 
"function () {
  console.log('println');
}", but I feel like this would make the code nicer.

Thanks,
JPD

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Silence "WARNING: Long already refers to: class java.lang.Long in namespace: ..." in aot compile compatible way

[Scott Nielsen]

I have a simplified scenario here: https://github.com/scizo/unmap-failure

The problem is I am using ns-unmap to prevent a WARNING from being printed 
when shadowing java.lang.Long in a namespace.
When this code is aot compiled, the namespace var referenced by 'Long is 
being created before the ns-unmap is being executed causing the ns-unmap to 
unmap the desired 'Long and not java.lang.Long. Is there a way to silence 
the warning in a way that will work with both aot and non-aot compiled code?

Thanks for any help in advance,

Scott

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Re: complex numbers in clojure

[Mikera]

Complex numbers are tricky because:
- They need to be fast in order to be useful for numerical computing. The 
"obvious" implementations that you might create with boxed values, 
vectors/maps, multimethods and protocols are likely to be unacceptable for 
many use cases
- You still want to be able to use them in a generic way, with operations 
that play nicely with other values (Doubles etc.)

I have thought about this a lot w.r.t. core.matrix and have come to the 
conclusion that there is no simple, elegant answer that meets all use cases.

What I'd like to suggest is:
a) The community converge on a single, minimal, lightweight representation 
for a boxed complex scalar value. This is probably best as a Java class 
(for easy interop with Java libraries). I 
think 
http://commons.apache.org/proper/commons-math/apidocs/org/apache/commons/math3/complex/Complex.html
 
is a good candidate
b) A lightweight wrapper library that provides nice complex functions in 
Clojure, using the above type. Nothing fancy. But can make extensive use of 
type hints etc. for performance so should be pretty fast
c) A library using core.matrix that implements complex vectors, complex 
matrices etc but also uses a) for complex scalar values. This should use a 
underlying double-array backed implementation for performance, probably 
vectorz-clj would be best (though that could be hidden as an implementation 
detail). This library would also implement all the core.matrix protocols 
for the chosen complex number type, mostly just by calling b) directly


On Monday, 27 April 2015 23:39:34 UTC+8, Nik wrote:
>
> I have been thinking along the lines of mikera and Maik - and it seems 
> like there is no further progress here? I would like to take a crack at 
> creating a complex number type, but implemented as a library to Clojure. I 
> am not sure where to start, and if anyone here has suggestions, I'd be 
> happy to hear them. 
>
> A complex number could simply be a vector of two elements, or a map with 
> :real and :imag keys (or something lightweight) - and I am not sure what it 
> would require to make this type work happily with code arithmetic functions 
> in Clojure and Java Math. 
>
> It would also have to work with seq operations in Clojure - for instance: 
> If I have a complex number c = {:real 3 :imag 4}, and a vector v = [1 -2 
> c], it would be nice to have the call 'map #(Math/abs %) v' produce (1 2 
> 5). 
>
> I am having trouble figuring out all the pieces that need to be 
> implemented. Is it even possible to implement this as a library, or does 
> this need to be a part of clojure.core?
>

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Re: Crazy Need: Embed JavaScript Structure in Clojure

[Atamert Ölçgen]

Hi JPatrick,

On Mon, Apr 27, 2015 at 11:50 PM, JPatrick Davenport 
wrote:

> Hello,
> So just to get it out: I do not want to evaluate the JavaScript, simply
> preserve it.
>
> I'm working on an ArangoDB driver. Part of the wonder that is ArangoDB is
> its ability to support transactions. This is done using JSON. Part of the
> REST object for a transaction is what I want to do in the transaction. This
> is encapsulated in the "action" attribute of the posted JSON object.
>
> Here's an example
> {...JSON configuration
>  action: "function (){many lines of stuff here",
>  More JSON configuration}
>
> Now the way that this works in node is by converting the function into a
> String. I didn't know that String(function () {..valid JavaScript...})
> would kick out a string version of the function. Pretty neat.
>
> I want to do the same thing with Clojure. I presently take a map with one
> of the attributes of :action. I want something like this.
> {:some-key :some-value,
>  :action  (js-macro function(){
>   console.log("pretty crappy transaction");
>   console.log("another line");
> })}
>
> On the other side of the macro I want to get "function() {\t\t\t\n
> console.log(\"pretty crappy transaction\";\n\t\t\tconsole.log(\"another
> line\");\n} or there about.
>
> I've got
>
> (defmacro js [& js-fun]
>
> (let [body (str js-fun)]
>
> (subs body 1 (- (count body) 1
>
> That gets the idea. Unfortunately, I loose the ";" as well as the new
> lines.
>

Your macro thinks it receives the code as a string, but Clojure macros
receive their parameters as s-expressions. Just like functions, with the
only difference functions' params are evaluated.



>
> I'm pretty sure I don't *need* this macro. I can probably get away with
> "function () {
>   console.log('println');
> }", but I feel like this would make the code nicer.
>

Perhaps you can write a function that builds a function somewhere and then
outputs a string containing JavaScript code that invokes it.

(defn js [& body]
  (eval `(defn fn-name# [] ~@body))
  (str "function() { your.ns." fn-name# "(); }"))


(I didn't test the code, it's just to give you an idea.)




>
> Thanks,
> JPD
>
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Kind Regards,
Atamert Ölçgen

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