A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[Jacek Laskowski]

Hi,

Is it intended in 1.3-alpha2? I think the error message in 1.2 is way
better (although not as user friendly as I wish to). Shall I report
it? Where? How?

devmac:~ jacek$ clj -13
CLOJURE_DIR:  /Users/jacek/apps/clojure
CLOJURE_CONTRIB_JAR:  /Users/jacek/apps/clojure-contrib-1.3.0-alpha2.jar
Clojure 1.3.0-alpha2
user=> (def c)
#'user/c
user=> c
#

devmac:~ jacek$ clj
CLOJURE_DIR:  /Users/jacek/apps/clojure-1.2.0
CLOJURE_CONTRIB_JAR:
/Users/jacek/apps/clojure-contrib/target/clojure-contrib-1.2.0.jar
Clojure 1.2.0
user=> (def c)
#'user/c
user=> c
java.lang.IllegalStateException: Var user/c is unbound. (NO_SOURCE_FILE:0)

Jacek

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Supporting 1.2 and 1.3

[Saul Hazledine]

Hello,
  I've put some small libraries on github. At the moment they
specifically depend on Clojure 1.2 and contrib (since its the released
version). However, I have had requests to take out the dependencies on
clojure and contrib so that they don't infect projects that use them.
Is this standard practice? Would it catch people out?

I thought about alternative approaches but have no solution. For
instance, in Leiningen, it is possible to specify a minimal version
e.g
[org.clojure/clojure-contrib "[1.2,)"]

This would normally be fine but in 1.3 the dependency on contrib
changes:

[org.clojure.contrib/standalone "1.3.0-alpha2"]

Has anyone hit this problem? What is the best way of dealing with it?

Thanks in advance for any help.
Saul

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Re: Some questions about Clojure Protocols

[nicolas.o...@gmail.com]

I see your point.
Somehow, it is annoying to have to manipulate a set of protocols that
always go together.
And it would be nice to have a shorthand.

I have a very small prototype here:

git://nicolasoury.repositoryhosting.com/nicolasoury/type-classes.git

of some code to allow "type-classes" like deductions of protocols (ie
logical programming with protocols).

It is not really working, tested, maintained or nice currently.
(It was just a quick proof of concept)

The idea is to write a rule:

Serializable, Comparable, HalfCool => Cool  {implemenation of
functions that are not in the pre-condition}

Typically if you roll you own Eq protocol with eq,

Comparable => Eq {:eq (fn [x y] (compare x y)}

Then, for each protocol accessible on a right handside of a rule, it
extends Object with that protocol.

This default implementation try to apply all rules, in order to deduce
an implementation.
If it deduces an implementation, it extends the protocol with that
implementation, for the type of the argument.
(That way there is a derivation of implementation only on the first call)

The implementation is very bad (and not maintained) and I wouldn't
advise using it, but the idea can be useful sometimes.

Especially, it shows that the access you have to protocols at the
programmatic level, might help to solve the kind of problems you have.
(this kind of deduction are a bit of an overkill for the problem at hand)

I don't know if there is a similar programmatic  access to deftype. I
would like to know of it if there is.

Best,

Nicolas.

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Re: Some questions about Clojure Protocols

[Shantanu Kumar]

For complex cases, you may like to fall back on multi-methods and
abstraction types. I blogged about typed abstractions few days ago
here:

http://bitumenframework.blogspot.com/2010/10/typed-abstractions-in-clojure.html

Regards,
Shantanu

On Nov 4, 1:25 pm, "nicolas.o...@gmail.com" 
wrote:
> I see your point.
> Somehow, it is annoying to have to manipulate a set of protocols that
> always go together.
> And it would be nice to have a shorthand.
>
> I have a very small prototype here:
>
> git://nicolasoury.repositoryhosting.com/nicolasoury/type-classes.git
>
> of some code to allow "type-classes" like deductions of protocols (ie
> logical programming with protocols).
>
> It is not really working, tested, maintained or nice currently.
> (It was just a quick proof of concept)
>
> The idea is to write a rule:
>
> Serializable, Comparable, HalfCool => Cool  {implemenation of
> functions that are not in the pre-condition}
>
> Typically if you roll you own Eq protocol with eq,
>
> Comparable => Eq {:eq (fn [x y] (compare x y)}
>
> Then, for each protocol accessible on a right handside of a rule, it
> extends Object with that protocol.
>
> This default implementation try to apply all rules, in order to deduce
> an implementation.
> If it deduces an implementation, it extends the protocol with that
> implementation, for the type of the argument.
> (That way there is a derivation of implementation only on the first call)
>
> The implementation is very bad (and not maintained) and I wouldn't
> advise using it, but the idea can be useful sometimes.
>
> Especially, it shows that the access you have to protocols at the
> programmatic level, might help to solve the kind of problems you have.
> (this kind of deduction are a bit of an overkill for the problem at hand)
>
> I don't know if there is a similar programmatic  access to deftype. I
> would like to know of it if there is.
>
> Best,
>
> Nicolas.

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Re: clojure-backtracking-monads .. can it emulate prolog?

[Sunil S Nandihalli]

Thanks David.
I am reading it .. it has nice description of mini-kanren.
I was wondering if there is predicate corresponding to prologs "nonvar" in
mini-kanren.
Sunil.

On Wed, Nov 3, 2010 at 10:13 PM, David Nolen  wrote:

> On Wed, Nov 3, 2010 at 12:38 PM, David Nolen wrote:
>
>> On Wed, Nov 3, 2010 at 11:53 AM, Sunil S Nandihalli <
>> sunil.nandiha...@gmail.com> wrote:
>>
>>> thanks Jim for your email. I will try to get my hands on Reasoned
>>> Schemer.. :)
>>> Sunil.
>>>
>>
> William Byrd's dissertation, http://gradworks.umi.com/33/80/3380156.htmlis a 
> great source for context, additional info, prior research, papers, etc.
>
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Re: Supporting 1.2 and 1.3

[Shantanu Kumar]

Ring has a 1.3 branch to deal with the new version, for example. Maybe
that's one solution.

Regards,
Shantanu

On Nov 4, 12:44 pm, Saul Hazledine  wrote:
> Hello,
>   I've put some small libraries on github. At the moment they
> specifically depend on Clojure 1.2 and contrib (since its the released
> version). However, I have had requests to take out the dependencies on
> clojure and contrib so that they don't infect projects that use them.
> Is this standard practice? Would it catch people out?
>
> I thought about alternative approaches but have no solution. For
> instance, in Leiningen, it is possible to specify a minimal version
> e.g
> [org.clojure/clojure-contrib "[1.2,)"]
>
> This would normally be fine but in 1.3 the dependency on contrib
> changes:
>
> [org.clojure.contrib/standalone "1.3.0-alpha2"]
>
> Has anyone hit this problem? What is the best way of dealing with it?
>
> Thanks in advance for any help.
> Saul

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Re: Bug with instance? inside deftypes

[Christophe Grand]

To me its an implementation wart which is dictated by the use of the
reflection API in the compiler.
There is some work done by Stu to create a clojure reflection API with
several backends (eg ASM or Java Reflection).
However I won't bet on the *current* compiler being fixed.

my 2 cents

Christophe

On Thu, Nov 4, 2010 at 4:09 AM, ka  wrote:

> >> I would guess the problem is referring to T inside the deftype.
>
> This also works:
>
> (deftype T [] Object (equals [this o] (if (= T (class o)) true
> false)))
>
> But as Meikel said hope that this is not the end of the story.
>
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Re: A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[Ken Wesson]

On Thu, Nov 4, 2010 at 3:41 AM, Jacek Laskowski  wrote:
> Hi,
>
> Is it intended in 1.3-alpha2? I think the error message in 1.2 is way
> better (although not as user friendly as I wish to). Shall I report
> it? Where? How?
>
> devmac:~ jacek$ clj -13
> CLOJURE_DIR:  /Users/jacek/apps/clojure
> CLOJURE_CONTRIB_JAR:  /Users/jacek/apps/clojure-contrib-1.3.0-alpha2.jar
> Clojure 1.3.0-alpha2
> user=> (def c)
> #'user/c
> user=> c
> #
>
> devmac:~ jacek$ clj
> CLOJURE_DIR:  /Users/jacek/apps/clojure-1.2.0
> CLOJURE_CONTRIB_JAR:
> /Users/jacek/apps/clojure-contrib/target/clojure-contrib-1.2.0.jar
> Clojure 1.2.0
> user=> (def c)
> #'user/c
> user=> c
> java.lang.IllegalStateException: Var user/c is unbound. (NO_SOURCE_FILE:0)

Looks like an attempt to make commonplace compile error messages less
verbose, to me.

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Re: clojure-backtracking-monads .. can it emulate prolog?

[David Nolen]

On Thu, Nov 4, 2010 at 6:16 AM, Sunil S Nandihalli <
sunil.nandiha...@gmail.com> wrote:

> Thanks David.
> I am reading it .. it has nice description of mini-kanren.
> I was wondering if there is predicate corresponding to prologs "nonvar" in
> mini-kanren.
> Sunil.
>

Again, I don't know enough about Prolog, but isn't this considered one of
Prolog's non-logical operators? I think miniKaren attempts to avoid them.

David

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Re: Some questions about Clojure Protocols

[Paul Hobbs]

Meikel,

Strong type systems make programming in the large easier.  It would be nice
if I didn't have to walk on eggshells when using a library.  Written
agreements are also known as "gotchas".

--
Paul Hobbs


On Wed, Nov 3, 2010 at 11:30 PM, Meikel Brandmeyer  wrote:

> Hi,
>
> On 4 Nov., 04:58, ka  wrote:
>
> > (defprotocol OnlyHalfCooless x y z)
> >
> > Instead of
> > (defn is-this-cool? [o] (satisfies? Coolness o))
> >
> > I need to now write:
> > (defn is-this-cool? [o] (or (instance? Cool1 o) (instance? Cool2 o))
> > or, (even worse)
> > (defn is-this-cool? [o] (and (satisfies? OnlyHalfCoolness o)
> > (instance? Comparable o) (instance? Serializable o))
>
> May I ask a heretic question: Why don't you specify the contract in
> the docstring of the protocol?
>
> (defprotocol Coolness
>  "Yadddayaddablablablubber.
>  Cool things have to be Comparable and Serializable."
>  (x ..)
>  (y ...))
>
> If someone doesn't adhere to this contract, it's his program which is
> broken, not yours.
>
> Sincerely
> Meikel
>
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Re: Some questions about Clojure Protocols

[Laurent PETIT]

Well,

I'm not totally sure about what I'll write below, but I'll still try
to make a decent job of sharing my current thoughts:

  * first, when I see calls to (instance?) (satisifies?), it rings a
bell in my head. "design problem".
  * second, it seems like you're trying to "fix in the concrete"
something which may not have to. Having "coolness" be a static
property of implementing this and that protocol seems very "fixed".
Beware the fixed hierarchies in java when you then have hard times
getting orthogonal code (given that java has no implementation
multiple inheritence, for example). But maybe it's just the example
(or even me not totally understanding the example).
  * third: looks like a protocol abuse. I have the impression that the
current "trend" is to see protocols as fine-grained "extension points"
of generic algorithms. Which implies that the public API is not
protocol functions, but those "regular functions" to which you pass
objects which happen to be extended to some protocols (with you the
consumer being aware of it or not).

So a library implementer has designed some interesting generic
functions. He organizes the way these generic functions deal with
different types of input by creating protocols and calling protocol
functions on the inputs, and extends those protocols to the most
relevant kinds of input types (for him). He then decides to make the
protocols part of his public API to let you, the user, have the
ability to benefit from the generic functions for your own specific
kinds of types.
In this scheme, the goal is less "extending the protocol for the sake
of it" than "extending the protocol to be able to leverage existing
functions *using* the protocols to one's particular kind of
types/records".

If the design of your application requires the use of protocols at
all, which should generally not be an implicit assumption, IMHO.

2010/11/4 ka :
>> AFAIK, it is not possible. You must implement all the different protocols.
>> It might look desapointing, but on the other hand it is not necessary.
>> (As there is no static typing in Clojure)
>> What is your use-case?
>
> Current use case is that I want an abstraction which comprises of a
> set of operations I want + Comparable + Serializable
>
>> Just define types that extend all the protocols.
>> You can't. But you can define a type that extends both P and Comparable.
>
> Currently I'm struggling with the following problem - Suppose I
> consider something satisfying 'Coolness' property if it does x, y, z +
> is comparable + serializes.
>
> To do this I create a protocol 'OnlyHalfCoolness':
> (defprotocol OnlyHalfCooless x y z)
>
> and two deftypes Cool1, Cool2:
> (deftype Cool1 ... OnlyHalfCoolness .. Comparable .. Serializable)
> (deftype Cool2 ... OnlyHalfCoolness .. Comparable .. Serializable)
>
> Now I need to write a function: is-this-cool?
>
> Instead of
> (defn is-this-cool? [o] (satisfies? Coolness o))
>
> I need to now write:
> (defn is-this-cool? [o] (or (instance? Cool1 o) (instance? Cool2 o))
> or, (even worse)
> (defn is-this-cool? [o] (and (satisfies? OnlyHalfCoolness o)
> (instance? Comparable o) (instance? Serializable o))
>
> A type hierarchy is not required - but I think a way to compose
> (atleast union) abstractions would be nice.
>
> Are there some fundamental problems with - (defprotocol Coolness ..
> Comparable .. Serializable .. x y z) ?
>
>> What do you mean by "static" functions?
>
> Normal functions which do not dispatch based on the type of their
> first argument. Forget about this - thinking more about it - they
> don't really make too much sense in protocols.
>
>
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Re: Some questions about Clojure Protocols

[Mike Meyer]

On Thu, 4 Nov 2010 00:50:35 -0700
Paul Hobbs  wrote:

> Strong type systems make programming in the large easier. 


Paul,

"Strong typing" has so many definitions that your statement is nearly
meaningless. See http://www.wordiq.com/definition/Strong_typing for a
few.

Now, if you have some prove that's not just anecdotal, I'd be
interested in hearing. Likewise if someone has prove of the contrary.

   Thanks,
http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.

O< ascii ribbon campaign - stop html mail - www.asciiribbon.org

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Re: Some questions about Clojure Protocols

[Meikel Brandmeyer]

Hi,

On 4 Nov., 08:50, Paul Hobbs  wrote:

> Strong type systems make programming in the large easier.  It would be nice
> if I didn't have to walk on eggshells when using a library.  Written
> agreements are also known as "gotchas".

I'm not sure what you mean with "strong" type systems. Clojure's type
system is dynamic. That means if I call seq on a thing I better make
sure that I have an actually seqable thing. Otherwise I get a
RuntimeException during runtime of my program. How is that different
to a protocol function implementation trying to compare two things? If
at least one doesn't implement Comparable you'll get a runtime
exception. I take it you expect static typing.

That said, I sense a lot of object-oriented thinking in how protocols
are seen in the moment. From my point of view, a honest definition of
a type or record is:

(defrecord Abc [a b c])

(extend-protocol Xyz
  Abc
  (x [this] ...)
  ...)

The record has nothing to do with the protocol. The record is a
collection of data with a special name representing a value of some
special sort. A protocol comprises functions which act on data in a
certain abstract way. How this works for different types of data is
defined by extending the protocol to the type (and not vice versa;
extend-type is a suboptimal way to carry this meaning). That you
specify these implementation inline with the type definition is a way
to improve performance. But I would even call it pre-mature
optimisation in a philosophical way. At the moment I see protocols
just as functions acting on data as any other "normal" function does
also.

But I'm not sure I understand the philosophy of protocols myself. Some
the above may be totally off track. YMMV.

Sincerely
Meikel

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Re: A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[lprefontaine]

Rich at the Conj explained that he wanted to remove a bunch of 
verifications each time a value was referenced to gain some speed.
The basis was of his reasoning was that an unbound
value is an exception more than a common thing and all these verifications at 
run time were really slowing things significantly for all applications.

I recalls that he mentioned he needed to "create" the unbound value to achieve
these optimizations.

Luc P.

Ken Wesson  wrote ..
> On Thu, Nov 4, 2010 at 3:41 AM, Jacek Laskowski  
> wrote:
> > Hi,
> >
> > Is it intended in 1.3-alpha2? I think the error message in 1.2 is way
> > better (although not as user friendly as I wish to). Shall I report
> > it? Where? How?
> >
> > devmac:~ jacek$ clj -13
> > CLOJURE_DIR:  /Users/jacek/apps/clojure
> > CLOJURE_CONTRIB_JAR:  /Users/jacek/apps/clojure-contrib-1.3.0-alpha2.jar
> > Clojure 1.3.0-alpha2
> > user=> (def c)
> > #'user/c
> > user=> c
> > #
> >
> > devmac:~ jacek$ clj
> > CLOJURE_DIR:  /Users/jacek/apps/clojure-1.2.0
> > CLOJURE_CONTRIB_JAR:
> > /Users/jacek/apps/clojure-contrib/target/clojure-contrib-1.2.0.jar
> > Clojure 1.2.0
> > user=> (def c)
> > #'user/c
> > user=> c
> > java.lang.IllegalStateException: Var user/c is unbound. (NO_SOURCE_FILE:0)
> 
> Looks like an attempt to make commonplace compile error messages less
> verbose, to me.
> 
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Re: Resources on optimizing Clojure code

[cej38]

It is wonderful that people are so willing to help with a specific
problem, and I encourage you to continue doing so, but I don't think
anyone has answered the real question.  Is there material out there
that describes some of the mechanisms, tools, ideas, etc. that will
allow the average clojure user to optimize their code.  Yes, Yes, a
good implementation is key, but you need to know the best practices in
order to develop that implementation.

Not that I have done this myself (yet!) but there are some that argue
that reimplementing certain time critical components as macros will
greatly speed up the code.  See the link below:
http://www.bestinclass.dk/index.clj/2010/03/functional-fluid-dynamics-in-clojure.html

Optimization is a topic that I would like to see more on.






On Nov 2, 1:32 pm, Dan Kefford  wrote:
> Hello fellow clojurians...
>
> I've been using Clojure now fairly regularly for the past two months
> solving problems on Project Euler. I've been fairly successful solving
> them but there are times where the performance of my code either
> stinks (the answer may come back in 5-10 minutes) or not at all even
> though I have effectively solved the problem (the code is correct and
> will return the answer for n < 1000 but for n < 10^8... forget about
> it.)
>
> My question is: are there any materials out there on how to optimize
> performance of Clojure code? There doesn't seem to be a lot out there.
>
> Thanks in advance,
>
> dan kefford

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Re: Is this bug in Google AppEngine, appengine-clj or Clojure itself?

[Miki]

FYI: 0.4.1-SNAPSHOT has this fix

On Nov 3, 11:07 am, Miki  wrote:
> Does anybody know if this fix made it to the released jar?
>
> On Oct 17, 12:18 am, Mike Hinchey  wrote:
>
> > I think it is caused by those 2 clojure bugs (which seem to be the same
> > thing).  You may be able to work around that problem by patching
> > appengine-clj to hint the method call to be on the public interface:
> > DatastoreService.
>
> > (defn current-transaction
> >   "Returns the current datastore transaction, or nil if not within a
> > transaction." [] (.getCurrentTransaction
> > ^com.google.appengine.api.datastore.DatastoreService
> > (datastore) nil))

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Documentation lacking for ns macro

[Ken Wesson]

The ns macro seems to be poorly documented as yet. The Namespaces page
at the main Clojure site does not go into detail about its syntax;
"doc ns" comes closer, with:

  (ns foo.bar
(:refer-clojure :exclude [ancestors printf])
(:require (clojure.contrib sql sql.tests))
(:use (my.lib this that))
(:import (java.util Date Timer Random)
 (java.sql Connection Statement)))

given as an example. But what exactly, for instance, is the use clause
really supposed to look like? Is that a list of libraries starting
with my.lib, for example, or is it a single lib and a list of symbols?
The accompanying text only suggests looking at the use function's
documentation. But using "doc use" gives:

clojure.core/use
([& args])
  Like 'require, but also refers to each lib's namespace using
  clojure.core/refer. Use :use in the ns macro in preference to calling
  this directly.

  'use accepts additional options in libspecs: :exclude, :only, :rename.
  The arguments and semantics for :exclude, :only, and :rename are the same
  as those documented for clojure.core/refer.

Yeah, that's a real help if you're trying to remember the syntax. "&
args". How specific. :)

I think this is one area that could definitely use improvement,
including a couple of actual examples of usage on the Namespaces page
and a better description of the arglist for the use function (and
ditto require) as well as a better :use example in "doc ns". The model
here should be the example :import clause above, which is perfect --
it's clear that it should be followed by lists that start with a
package and continue with classnames from that package. By contrast,
it's not clear from all of this exactly how to use :use and :require.
Studying (or copying and modifying) example code from elsewhere seems
to be the way to do it and I think it's suboptimal when that's the
ONLY way.

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Re: A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[Laurent PETIT]

Luc is right.

As to explain the behavior, see below:

2010/11/4 Jacek Laskowski :
> Hi,
>
> Is it intended in 1.3-alpha2? I think the error message in 1.2 is way
> better (although not as user friendly as I wish to). Shall I report
> it? Where? How?
>
> devmac:~ jacek$ clj -13
> CLOJURE_DIR:  /Users/jacek/apps/clojure
> CLOJURE_CONTRIB_JAR:  /Users/jacek/apps/clojure-contrib-1.3.0-alpha2.jar
> Clojure 1.3.0-alpha2
> user=> (def c)
> #'user/c
> user=> c
> #

c has the value "Unbound". The semantic has not changed, the way to
carry the semantic has.

Now if you try to really "use" c, for example use it in call position,
then since Unbound implements IFn, you'll have the appropriate
exception because it correctly overrides IFn's invoke(...) methods.

>
> devmac:~ jacek$ clj
> CLOJURE_DIR:  /Users/jacek/apps/clojure-1.2.0
> CLOJURE_CONTRIB_JAR:
> /Users/jacek/apps/clojure-contrib/target/clojure-contrib-1.2.0.jar
> Clojure 1.2.0
> user=> (def c)
> #'user/c
> user=> c
> java.lang.IllegalStateException: Var user/c is unbound. (NO_SOURCE_FILE:0)



>
> Jacek
>
> --
> Jacek Laskowski
> Notatnik Projektanta Java EE - http://jaceklaskowski.pl
>
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Python is way faster than Clojure on this task

[Pepijn de Vos]

Hi all,

I have written a Python script to analyze Minecraft levels and render a graph. 
Then I did the same with Clojure. It takes Python 10 seconds to analyze a map, 
while it takes Clojure over a minute.

After having tried different options without any significant improvement, I am 
lost as to why there is such a huge difference. I wouldn't mind an extra pair 
of eyes/brains to look at this.

I blogged about it in more detail here: 
http://pepijndevos.nl/clojure-versus-python
Clojure version: https://github.com/pepijndevos/Clomian/
Python version: https://github.com/l0b0/mian

Clojure spends most of its time in the freqs function, here are a couple of 
variations: https://gist.github.com/663096

If you want to run the code yourself, you'll need a Minecraft level and JNBT, 
which is not on Maven.
JNBT: http://jnbt.sourceforge.net/
The level used in the blogpost: http://dl.dropbox.com/u/10094764/World2.zip

Groeten,
Pepijn de Vos
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http://pepijndevos.nl

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Re: Python is way faster than Clojure on this task

[Mike Meyer]

On Thu, 4 Nov 2010 22:28:12 +0100
Pepijn de Vos  wrote:

> Hi all,
> 
> I have written a Python script to analyze Minecraft levels and render a 
> graph. Then I did the same with Clojure. It takes Python 10 seconds to 
> analyze a map, while it takes Clojure over a minute.
> 
> After having tried different options without any significant improvement, I 
> am lost as to why there is such a huge difference. I wouldn't mind an extra 
> pair of eyes/brains to look at this.
> 
> I blogged about it in more detail here: 
> http://pepijndevos.nl/clojure-versus-python
> Clojure version: https://github.com/pepijndevos/Clomian/
> Python version: https://github.com/l0b0/mian
> 
> Clojure spends most of its time in the freqs function, here are a couple of 
> variations: https://gist.github.com/663096
> 
> If you want to run the code yourself, you'll need a Minecraft level and JNBT, 
> which is not on Maven.
> JNBT: http://jnbt.sourceforge.net/
> The level used in the blogpost: http://dl.dropbox.com/u/10094764/World2.zip

Can you check GC activity in the clojure version?

I once ran into an issue where Python was running rings around an
Eiffel version (compiled down to native code - no VM need apply). This
looks similar to what you have, in that I built a large data
structure, and then started groveling over it. Turned out that Eiffel
was doing a mark-and-sweep GC, which was spending all of it's time
marking and sweeping the large static data structure, whereas python
doing a reference count GC didn't. Given that I know nothing about
Java GCs, this is just a WAG.

Come to think of it, how about trying to run the program Jython? That
should have the same GC issues. If it's some similar environmental
problem, that would show up there as well.

  http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.

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Tryclojure - A Call To Action

[Rayne]

http://blog.acidrayne.net/?p=25

I wrote this blog post in the hopes that I can motivate people to
contribute to tryclojure. http://try-clojure.org is a relatively
important website that is unfortunately subpar. I hope that with the
community's help, we can turn it into something spectacular.

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Re: Python is way faster than Clojure on this task

[Andrew Gwozdziewycz]

On Thu, Nov 4, 2010 at 5:43 PM, Mike Meyer
 wrote:
> On Thu, 4 Nov 2010 22:28:12 +0100
> Pepijn de Vos  wrote:
>
>> Hi all,
>>
>> I have written a Python script to analyze Minecraft levels and render a 
>> graph. Then I did the same with Clojure. It takes Python 10 seconds to 
>> analyze a map, while it takes Clojure over a minute.
>>
>> After having tried different options without any significant improvement, I 
>> am lost as to why there is such a huge difference. I wouldn't mind an extra 
>> pair of eyes/brains to look at this.
>>
>> I blogged about it in more detail here: 
>> http://pepijndevos.nl/clojure-versus-python
>> Clojure version: https://github.com/pepijndevos/Clomian/
>> Python version: https://github.com/l0b0/mian
>>
>> Clojure spends most of its time in the freqs function, here are a couple of 
>> variations: https://gist.github.com/663096
>>
>> If you want to run the code yourself, you'll need a Minecraft level and 
>> JNBT, which is not on Maven.
>> JNBT: http://jnbt.sourceforge.net/
>> The level used in the blogpost: http://dl.dropbox.com/u/10094764/World2.zip
>
> Can you check GC activity in the clojure version?
>
> I once ran into an issue where Python was running rings around an
> Eiffel version (compiled down to native code - no VM need apply). This
> looks similar to what you have, in that I built a large data
> structure, and then started groveling over it. Turned out that Eiffel
> was doing a mark-and-sweep GC, which was spending all of it's time
> marking and sweeping the large static data structure, whereas python
> doing a reference count GC didn't. Given that I know nothing about
> Java GCs, this is just a WAG.
>
> Come to think of it, how about trying to run the program Jython? That
> should have the same GC issues. If it's some similar environmental
> problem, that would show up there as well.

There are many different collectors for the JVMs, too numerous to list
here, all tunable.

http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html


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Re: Resources on optimizing Clojure code

[Gary Poster]

On Nov 4, 2010, at 1:32 PM, cej38 wrote:

> It is wonderful that people are so willing to help with a specific
> problem, and I encourage you to continue doing so, but I don't think
> anyone has answered the real question.  Is there material out there
> that describes some of the mechanisms, tools, ideas, etc. that will
> allow the average clojure user to optimize their code.  

Chapter 12 of Joy of Clojure is about performance (type hints, transience, 
chunked sequences, memoization, coercion).

Arguably much of the book is also about what you describe broadly, since it is 
trying to teach and encourage efficient, idiomatic Clojure usage generally, 
AIUI.

Gary

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using swig in clojure

[Seth]

Ive recently had troubles using swig in clojure getting a 'unsatisfied
link exception' even though using the swig generated library worked in
regular java code. I believe there was a post on this somewhere in
these google groups.

Anyways, I have figured out that if I place the following code in a
clojure file (test.clj)
(System/loadLibrary "Seth")

and go (compile 'test) on the REPL, i get


No such file or directory
  [Thrown class java.io.IOException]

Restarts:
 0: [QUIT] Quit to the SLIME top level

Backtrace:
  0: java.io.UnixFileSystem.createFileExclusively(Native Method)
  1: java.io.File.createNewFile(File.java:900)
  2: clojure.lang.Compiler.writeClassFile(Compiler.java:5885)
  3: clojure.lang.Compiler.compile(Compiler.java:6043)
  4: clojure.lang.RT.compile(RT.java:368)
  5: clojure.lang.RT.load(RT.java:407)
  6: clojure.lang.RT.load(RT.java:381)
  7: clojure.core$load$fn__4511.invoke(core.clj:4905)
  8: clojure.core$load.doInvoke(core.clj:4904)
  9: clojure.lang.RestFn.invoke(RestFn.java:409)
 --more--




However, afterwards i can succesfully do
(import Seth)
(Seth/add 2 3) => 5

I cant do the loadlibrary thing on the repl, or it wont work (i get
the 'unsatisfied link error' when calling (Seth/add)).  Notice that if
I do (compile 'test) again i get the same error above, which is
weird because if i do (System/loadLibrary "Seth") on the repl i get
the 'expected' error

Native Library /home/seth/.random/java/libSeth.so already loaded in
another classloader
  [Thrown class java.lang.UnsatisfiedLinkError]

Restarts:
 0: [QUIT] Quit to the SLIME top level

Backtrace:
  0: java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1715)
  1: java.lang.ClassLoader.loadLibrary(ClassLoader.java:1675)
  2: java.lang.Runtime.loadLibrary0(Runtime.java:840)
  3: java.lang.System.loadLibrary(System.java:1047)
  4: user$eval1825.invoke(NO_SOURCE_FILE:1)
  5: clojure.lang.Compiler.eval(Compiler.java:5424)
  6: clojure.lang.Compiler.eval(Compiler.java:5391)
  7: clojure.core$eval.invoke(core.clj:2382)
 --more--




Anyone know whats going on and how this can be fixed?

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Re: A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[Jacek Laskowski]

On Thu, Nov 4, 2010 at 8:39 PM, Laurent PETIT  wrote:

> c has the value "Unbound". The semantic has not changed, the way to
> carry the semantic has.
>
> Now if you try to really "use" c, for example use it in call position,
> then since Unbound implements IFn, you'll have the appropriate
> exception because it correctly overrides IFn's invoke(...) methods.

It begs a question then, why would I do that? Where would that be of use?

devmac:~ jacek$ clj -13
CLOJURE_DIR:  /Users/jacek/apps/clojure
CLOJURE_CONTRIB_JAR:  /Users/jacek/apps/clojure-contrib-1.3.0-alpha2.jar
Clojure 1.3.0-alpha2
user=> (def c)
#'user/c
user=> (c)
IllegalStateException Attempting to call unbound fn: #'user/c
clojure.lang.Var$Unbound.throwArity (Var.java:43)
user=> (type c)
clojure.lang.Var$Unbound

Jacek

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Re: Tryclojure - A Call To Action

[box]

really like the site. i like the tutorial section. it would be nice if
the site would focus more on examples.

On Nov 4, 5:49 pm, Rayne  wrote:
> http://blog.acidrayne.net/?p=25
>
> I wrote this blog post in the hopes that I can motivate people to
> contribute to tryclojure.http://try-clojure.orgis a relatively
> important website that is unfortunately subpar. I hope that with the
> community's help, we can turn it into something spectacular.

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Re: Tryclojure - A Call To Action

[Rayne]

Right. One of the most important aspects of a site like this is it's
tutorial. The tutorial should be interactive, much like tryhaskell's
tutorial. That's one of the biggest things that needs to be done.

Beyond that, tutorial authors would be great as well. If somebody
feels like writing a tutorial section or improving the existing ones,
have at it. It's a great way to examine your own Clojure knowledge and
very helpfully contribute to the project at the same time.

On Nov 4, 6:36 pm, box  wrote:
> really like the site. i like the tutorial section. it would be nice if
> the site would focus more on examples.
>
> On Nov 4, 5:49 pm, Rayne  wrote:
>
>
>
> >http://blog.acidrayne.net/?p=25
>
> > I wrote this blog post in the hopes that I can motivate people to
> > contribute to tryclojure.http://try-clojure.orgisa relatively
> > important website that is unfortunately subpar. I hope that with the
> > community's help, we can turn it into something spectacular.

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Polymorphic protocols and containers....

[Mike Meyer]

It seems like the polymorphism of protocols breaks inside the
methods. This is a problem for having a function that's polymorphic
between an object and a container of the same objects.

For instance:

user=> (defprotocol Tune (tweek [this]))
Tune
user=> (deftype Knob [name] Tune (tweek [this] (println "Tweeked" name)))
user.Knob
user=> (def base (Knob. "base"))
#'user/base
user=> (tweek base)
Tweeked base
nil
user=> (def treble (Knob. "treble"))
#'user/treble
user=> (tweek treble)
Tweeked treble
nil
user=> (deftype Box [& knobs] Tune (tweek [this] (for [knob knobs] (tweek 
knob
user.Box
user=> (tweek (Box. base treble))
user=> (tweek (Box. base treble))
java.lang.IllegalArgumentException: Don't know how to create ISeq from: 
user.Knob
(user=> 

Where what I really want to happen is to tweek all the knobs in the
box. Unfortunately, tweek inside the method seems to be wired to the
method it's in, and no longer polymorphic. I've tried various ways to
get to the variable I want, and some hinting, but nothing seems to
change what I'm getting here.

Maybe I shouldn't be trying to use protocols and types for this? Can
someone let me know what I need to do to make this happen?

Thanks,
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Re: Tryclojure - A Call To Action

[Eric Lavigne]

Last time I introduced someone to Clojure via try-clojure.org, he came
back later and said that the console ignored him after a while, and he
wasn't sure what he did wrong. We tried it together, and after a
couple minutes it stopped evaluating expressions. Does this bug sound
familiar? Unfortunately, I haven't been able to reproduce it since.

I'm guessing this is related to the bugfixes in jquery-console that
you mentioned, so upgrading to the latest version of jquery-console is
the piece that I would want to take on.

For my own reference, these are the customizations you made to
jquery-console that I will need to watch out for:

 
https://github.com/Raynes/tryclojure/commits/master/resources/public/javascript/jquery.console.js


On Thu, Nov 4, 2010 at 5:49 PM, Rayne  wrote:
> http://blog.acidrayne.net/?p=25
>
> I wrote this blog post in the hopes that I can motivate people to
> contribute to tryclojure. http://try-clojure.org is a relatively
> important website that is unfortunately subpar. I hope that with the
> community's help, we can turn it into something spectacular.
>

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Re: Tryclojure - A Call To Action

[Rayne]

That would be great. Any sort of problems with the console are very
likely to be related to jquery-console, so updating it might fix them.

I actually hadn't heard of that bug. Probably not a good sign, since
it might mean that people spend very little time with tryclojure. ;)

On Nov 4, 7:40 pm, Eric Lavigne  wrote:
> Last time I introduced someone to Clojure via try-clojure.org, he came
> back later and said that the console ignored him after a while, and he
> wasn't sure what he did wrong. We tried it together, and after a
> couple minutes it stopped evaluating expressions. Does this bug sound
> familiar? Unfortunately, I haven't been able to reproduce it since.
>
> I'm guessing this is related to the bugfixes in jquery-console that
> you mentioned, so upgrading to the latest version of jquery-console is
> the piece that I would want to take on.
>
> For my own reference, these are the customizations you made to
> jquery-console that I will need to watch out for:
>
>      https://github.com/Raynes/tryclojure/commits/master/resources/public/...
>
>
>
> On Thu, Nov 4, 2010 at 5:49 PM, Rayne  wrote:
> >http://blog.acidrayne.net/?p=25
>
> > I wrote this blog post in the hopes that I can motivate people to
> > contribute to tryclojure.http://try-clojure.orgis a relatively
> > important website that is unfortunately subpar. I hope that with the
> > community's help, we can turn it into something spectacular.

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Re: Polymorphic protocols and containers....

[Ken Wesson]

user=> (defn tweek* [knob] (tweek knob))
#'user/tweek*
user=> (tweek* base)
Tweeked base
nil
user=> (deftype Box [& knobs] Tune (tweek [this] (for [knob knobs]
(tweek* knob
user.Box
user=> (tweek (Box. base treble))
#

Not lexical scope, then -- it's not the deftype macro redefining it
lexically or that wouldn't make tweek* stop working.


user=> (defn tweek* [knobs] (pmap #(tweek %) knobs))
#'user/tweek*
user=> (tweek (Box. base treble))
#

Even more interesting. It's not being thread-locally rebound, either.
It's being globally rebound.


user=> (deftype Box [& knobs] Tune (tweek [this] (println this) (tweek* knobs)))
user.Box
user=> (tweek (Box. base treble))
#
#

Fascinating. It's not calling the Box tweek on the Box, then calling
the Box tweek again on the knobs, else we'd have seen

#
#
#http://groups.google.com/group/clojure?hl=en

Re: Tryclojure - A Call To Action

[Ken Wesson]

On Thu, Nov 4, 2010 at 8:58 PM, Rayne  wrote:
> That would be great. Any sort of problems with the console are very
> likely to be related to jquery-console, so updating it might fix them.
>
> I actually hadn't heard of that bug. Probably not a good sign, since
> it might mean that people spend very little time with tryclojure. ;)

Inability to paste into the repl at tryclojure is also a problem.

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Re: Tryclojure - A Call To Action

[pete mcquain]

I would love to help out.  I'm new to closure, but I'm a web dev by day.
What can I do?
On Nov 4, 2010 5:49 PM, "Rayne"  wrote:
> http://blog.acidrayne.net/?p=25
>
> I wrote this blog post in the hopes that I can motivate people to
> contribute to tryclojure. http://try-clojure.org is a relatively
> important website that is unfortunately subpar. I hope that with the
> community's help, we can turn it into something spectacular.
>
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Re: Tryclojure - A Call To Action

[Eric Lavigne]

Pete,

Would you feel comfortable working on the jquery-console upgrade?
That's entirely a Javascript issue, and I'd be happy to find another
piece to work on. I actually prefer working in Clojure, and only took
on the jquery-console upgrade task because it seemed important.

Let me know if you're going to do the jquery-console upgrade, in which
case I'll choose one of the other tasks.

Eric

On Thu, Nov 4, 2010 at 9:04 PM, pete mcquain  wrote:
> I would love to help out.  I'm new to closure, but I'm a web dev by day.
> What can I do?
>
> On Nov 4, 2010 5:49 PM, "Rayne"  wrote:
>> http://blog.acidrayne.net/?p=25
>>
>> I wrote this blog post in the hopes that I can motivate people to
>> contribute to tryclojure. http://try-clojure.org is a relatively
>> important website that is unfortunately subpar. I hope that with the
>> community's help, we can turn it into something spectacular.
>>
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Re: Tryclojure - A Call To Action

[Rayne]

I'm not sure, but I think I might have convinced Chris Done to allow
pasting into the REPL. In any case, all tutorial examples are
clickable (they are thrown into the REPL), which was my way of trying
to work around those issues. Anybody is welcome to patch tryclojure's
version of jquery-console (after the upgrade). However, if we start
making changes like this, it might be a good idea to fork the jquery-
console repository for our version.

On Nov 4, 8:03 pm, Ken Wesson  wrote:
> On Thu, Nov 4, 2010 at 8:58 PM, Rayne  wrote:
> > That would be great. Any sort of problems with the console are very
> > likely to be related to jquery-console, so updating it might fix them.
>
> > I actually hadn't heard of that bug. Probably not a good sign, since
> > it might mean that people spend very little time with tryclojure. ;)
>
> Inability to paste into the repl at tryclojure is also a problem.

There is lots to do! If you're decent with web design, then check out
the current design and see if you can make it better. I'm sure the
HTML is a mess, and heaven knows the CSS is probably a disaster, so
maybe you can help out with that. Making tryclojure look good is
important as well.

Beyond that, we have JavaScript stuff to do as well. Like Eric said,
jquery-console needs to be upgraded, and we need an interactive
tutorial a la tryhaskell.org, so that is some stuff you could look
into as well.

On Nov 4, 8:04 pm, pete mcquain  wrote:
> I would love to help out.  I'm new to closure, but I'm a web dev by day.
> What can I do?

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Re: Tryclojure - A Call To Action

[pete mcquain]

Sounds good to me. I'll start looking into it.
On Nov 4, 2010 9:15 PM, "Eric Lavigne"  wrote:
> Pete,
>
> Would you feel comfortable working on the jquery-console upgrade?
> That's entirely a Javascript issue, and I'd be happy to find another
> piece to work on. I actually prefer working in Clojure, and only took
> on the jquery-console upgrade task because it seemed important.
>
> Let me know if you're going to do the jquery-console upgrade, in which
> case I'll choose one of the other tasks.
>
> Eric
>
> On Thu, Nov 4, 2010 at 9:04 PM, pete mcquain 
wrote:
>> I would love to help out.  I'm new to closure, but I'm a web dev by day.
>> What can I do?
>>
>> On Nov 4, 2010 5:49 PM, "Rayne"  wrote:
>>> http://blog.acidrayne.net/?p=25
>>>
>>> I wrote this blog post in the hopes that I can motivate people to
>>> contribute to tryclojure. http://try-clojure.org is a relatively
>>> important website that is unfortunately subpar. I hope that with the
>>> community's help, we can turn it into something spectacular.
>>>
>>> --
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>>
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Re: Tryclojure - A Call To Action

[Rayne]

I'd like to remind you guys that if you plan to work on something,
please create an issue for it on Github and let me know, so that I can
assign your name to it with a tag and we can avoid duplicating work.

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Re: Some questions about Clojure Protocols

[ka]

> May I ask a heretic question: Why don't you specify the contract in the 
> docstring of the protocol?

Yes Meikel that is exactly what I have right now. Just trying to learn
and stir up a discussion here :)

Most times you'll just do fine by passing 'something' to Coolness
functions and expect them to work - they'll just blow up on runtime
(no .compareTo) if that 'something' isn't cool. But imagine certain
scary situations where that 'something' is really 'HalfCool' and still
some 'Coolness' functions work (type dispatch) behind your back!.

(defprotocol Coolness
  "Yadddayaddablablablubber.
  Cool things have to be Comparable and Serializable."
  (x .. "Since 'this' is cool i assume it is Serializable and
Comparable and so logically I can safely do this cool x thing!")
  (y ...))

(deftype ReallyCool ... Coolness .. Comparable .. Serializable)
(deftype SneakyCool .. Coolness)

(x (ReallyCool.)) ;yay rocket launches and reaches moon!
(x (SneakyCool.)) ;rocket launches alright (no exception thrown), but
blows mid air

I know you might argue its a code bug and caller's problem etc. - but
you just allowed a rocket to blow up.

Other times it might be necessary to know if something is 'Cool':

static public ISeq seq(Object coll){
  if(coll instanceof ASeq)
return (ASeq) coll;
  else if(coll instanceof LazySeq)
return ((LazySeq) coll).seq();
  else
return seqFrom(coll);
}

@Laurent,
> * first, when I see calls to (instance?) (satisifies?), it rings a bell in my 
> head. "design problem".
Do you see the above seq method as a design problem? - or if you don't
care about Java, consider clojure.walk.

If I understand you correctly (probability of which is less) you don't
really see protocols as defining abstractions - but just as a
convenient tool for polymorphism. Like:

(extend ReallyCool clojure.contrib.json/Write-JSON
  {:write-json ...})

But all of this discussion is kind of bypassing my original question,
Meikel you say:

> A protocol comprises functions which act on data in a certain abstract way.

I simply asked - is there anything fundamentally wrong with the notion
of those protocols being composable. Protocol P is a set of abstract
functions, can we have a convenient way of saying P = union(P1, P2) ?

On a related note how is this:

(defn dispatch-fn [this ..]
  (if (and (comparable? this) (serializable? this))
 :green-signal :red-signal)

(defmulti x dispatch-fn)
(defmulti y dispatch-fn)
(defmulti z dispatch-fn)

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Re: Tryclojure - A Call To Action

[pete mcquain]

Ok, sounds good (branch).  What stack/host is it being hosted on now?I've
got a couple crazy AppEngine ideas that have been floating around for the
past week or so.  Could be a good dogfooding example in itself.
-Pete -
On Nov 4, 2010 9:39 PM, "Rayne"  wrote:
> I'd like to remind you guys that if you plan to work on something,
> please create an issue for it on Github and let me know, so that I can
> assign your name to it with a tag and we can avoid duplicating work.
>
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Re: Bug with instance? inside deftypes

[ka]

Christophe, Is it reasonable to assume that atleast the documentation
should be modified to reflect the situation?

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Re: A bug? Unbound Unbound in 1.3-alpha2 when a symbol is not set

[David Nolen]

On Thu, Nov 4, 2010 at 7:09 PM, Jacek Laskowski wrote:

>
> It begs a question then, why would I do that? Where would that be of use?


The behavior has changed, for some context:

http://clojure-log.n01se.net/date/2010-10-18.html#12:12c

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Re: Tryclojure - A Call To Action

[Vilson Vieira]

Rayne I loved try clojure! Congrats! I really want to help but running
out of time for now. I'll take my hands on that as soon as possible.

Cheers.

2010/11/4 Rayne :
> Right. One of the most important aspects of a site like this is it's
> tutorial. The tutorial should be interactive, much like tryhaskell's
> tutorial. That's one of the biggest things that needs to be done.
>
> Beyond that, tutorial authors would be great as well. If somebody
> feels like writing a tutorial section or improving the existing ones,
> have at it. It's a great way to examine your own Clojure knowledge and
> very helpfully contribute to the project at the same time.
>
> On Nov 4, 6:36 pm, box  wrote:
>> really like the site. i like the tutorial section. it would be nice if
>> the site would focus more on examples.
>>
>> On Nov 4, 5:49 pm, Rayne  wrote:
>>
>>
>>
>> >http://blog.acidrayne.net/?p=25
>>
>> > I wrote this blog post in the hopes that I can motivate people to
>> > contribute to tryclojure.http://try-clojure.orgisa relatively
>> > important website that is unfortunately subpar. I hope that with the
>> > community's help, we can turn it into something spectacular.
>
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Re: Meta-circular STM for teaching purposes

[ka]

Hi Tom,

I might not be even remotely qualified but since I'm interested and
find the idea cool, so here's my take:

> - has anyone already experimented with a toy STM in Clojure for didactic 
> purposes?

No idea :)

> - what would be a good resource to start such a design from? (my current plan 
> is to start from )

I would think a good place to start is to define the primitives and
goals:
Primitives: assume existence of monitors in Clojure
Goals: Implement dosync in Clojure (hefty goal :))

I would love to help out in any capacity since I myself want to get
started with understand the STM in more detail. If you need a
volunteer you may contact me personally.

Thanks

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Re: Reloading java classes

[Seth]

All i need to do is a function to reload a class I specify, nothing
fancy. Surely there is some way?

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Re: Reloading java classes

[Dave Newton]

JRebel is still the best answer. Loading a class at runtime is non- trivial.
I don't know how it deals with handling existing instances of the class,
though; I still think CLOS got that right.

Dave
 On Nov 4, 2010 10:03 PM, "Seth"  wrote:
> All i need to do is a function to reload a class I specify, nothing
> fancy. Surely there is some way?
>
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Re: Tryclojure - A Call To Action

[Rayne]

It's currently hosted on Heinz's (Licenser's) server, which runs
apache.

On Nov 4, 9:22 pm, pete mcquain  wrote:
> Ok, sounds good (branch).  What stack/host is it being hosted on now?I've
> got a couple crazy AppEngine ideas that have been floating around for the
> past week or so.  Could be a good dogfooding example in itself.
> -Pete -

I wouldn't be opposed to a try[ruby|haskell]ish design. The designs
are very pretty. If anybody wants to go that route, I'd love to see
the results. :>

On Nov 4, 9:43 pm, Vilson Vieira  wrote:
> 2010/11/4 Rayne :
>
> > There is lots to do! If you're decent with web design, then check out
> > the current design and see if you can make it better. I'm sure the
> > HTML is a mess, and heaven knows the CSS is probably a disaster, so
> > maybe you can help out with that. Making tryclojure look good is
> > important as well.
>
> tryhaskell is a clone of why_'s tryruby [1]. We can do the same...
>
> [1]https://github.com/Sophrinix/TryRuby
>
> --
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>
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>
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>
> (((http://musa.cc)))

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Re: Tryclojure - A Call To Action

[Vilson Vieira]

2010/11/4 Rayne :
> There is lots to do! If you're decent with web design, then check out
> the current design and see if you can make it better. I'm sure the
> HTML is a mess, and heaven knows the CSS is probably a disaster, so
> maybe you can help out with that. Making tryclojure look good is
> important as well.

tryhaskell is a clone of why_'s tryruby [1]. We can do the same...

[1] https://github.com/Sophrinix/TryRuby

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Re: Some questions about Clojure Protocols

[David Nolen]

On Thu, Nov 4, 2010 at 10:17 PM, ka  wrote:

> > May I ask a heretic question: Why don't you specify the contract in the
> docstring of the protocol?
>
> (defprotocol Coolness
>  "Yadddayaddablablablubber.
>  Cool things have to be Comparable and Serializable."
>   (x .. "Since 'this' is cool i assume it is Serializable and
> Comparable and so logically I can safely do this cool x thing!")
>  (y ...))
>

This would be a terrible protocol - protocols do not compose in this manner.


> static public ISeq seq(Object coll){
>  if(coll instanceof ASeq)
>return (ASeq) coll;
>  else if(coll instanceof LazySeq)
>return ((LazySeq) coll).seq();
>  else
>return seqFrom(coll);
> }
>


> Do you see the above seq method as a design problem? - or if you don't
> care about Java, consider clojure.walk.
>

You can't fix Java so I'm not sure that's a legitimate example. clojure.walk
suffers from the "closed" property.


> If I understand you correctly (probability of which is less) you don't
> really see protocols as defining abstractions - but just as a
> convenient tool for polymorphism. Like:
>

polymorphism *is* a form of abstraction.


> I simply asked - is there anything fundamentally wrong with the notion
> of those protocols being composable. Protocol P is a set of abstract
> functions, can we have a convenient way of saying P = union(P1, P2) ?
>

 This is desirable, but it's not clear whether this should be a feature of
protocols themselves.


> On a related note how is this:
>
> (defn dispatch-fn [this ..]
>  (if (and (comparable? this) (serializable? this))
> :green-signal :red-signal)
>

Aha! Getting warmer.

This highlights a sore spot in the current multimethod implementation - the
dispatch fn is "closed". Rich has expressed several times that he would like
to see a predicate dispatch implementation for clojure that removes this
wart.

David

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clojure-mini kanren implementation of nonvar

[Sunil S Nandihalli]

Hello everybody,
I know that mini-kanren does not have "nonvar" I was trying to emulate its
effect by using

(cond-u
 ((& x :unassigned)
   fail)
  (succeed))

The idea is if x is not assigned it would successfully unify with
:unassigned (ofcourse I am assuming that none of the valid values can be
:unassigned ). So since I am using cond-u it would commit to the first
clause in which the first predicate would succeed and the next predicate
always fails  hence it would fail..

 (run q
 (exist [x]
(& x 10)
(cond-u
 ((& x :unassigned)
  fail)
 (succeed))
(& q 20)))

I tried the above code it is not having the expected behaviour .. Can
somebody help me with this ..?
Thanks,
Sunil.

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Re: Tryclojure - A Call To Action

[Rayne]

Not to discourage discussion here, but in case anybody missed it in
the blog post, we have a google group now if anybody wants to discuss
what they're doing, considering doing, or any ideas.
http://groups.google.com/group/tryclojure

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Re: Reloading java classes

[Christophe Grand]

If you launched your repl as a debug process in an IDE code hotswap
may work to some extent too.

Christophe

On Friday, November 5, 2010, Dave Newton  wrote:
> JRebel is still the best answer. Loading a class at runtime is non- trivial. 
> I don't know how it deals with handling existing instances of the class, 
> though; I still think CLOS got that right.
> Dave
>
> On Nov 4, 2010 10:03 PM, "Seth"  wrote:> All i need to do 
> is a function to reload a class I specify, nothing
>> fancy. Surely there is some way?
>>
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>
>
>
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On Clojure: http://clj-me.cgrand.net/ (en)

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Re: Polymorphic protocols and containers....

[Christophe Grand]

On Fri, Nov 5, 2010 at 1:39 AM, Mike Meyer <
mwm-keyword-googlegroups.620...@mired.org> wrote:

> It seems like the polymorphism of protocols breaks inside the
> methods. This is a problem for having a function that's polymorphic
> between an object and a container of the same objects.
>
> For instance:
>
> user=> (defprotocol Tune (tweek [this]))
> Tune
> user=> (deftype Knob [name] Tune (tweek [this] (println "Tweeked" name)))
> user.Knob
> user=> (def base (Knob. "base"))
> #'user/base
> user=> (tweek base)
> Tweeked base
> nil
> user=> (def treble (Knob. "treble"))
> #'user/treble
> user=> (tweek treble)
> Tweeked treble
> nil
> user=> (deftype Box [& knobs] Tune (tweek [this] (for [knob knobs] (tweek
> knob
>

this vector is not an argument list but a field list, so you are defiing to
fields, one named & and one named knobs.
Try to evaluate (.name (.knobs (Box. base treble))) and you'll see that
knobs only holds treble.

if you fix it:
(deftype Box [knobs] Tune (tweek [this] (for [knob knobs] (tweek knob

then:
(tweek (Box. [base treble]))

will work as expected.

If you really want var-args, you just have to write a factory fn
(defn box [& knobs] (Box. knobs))

hth,

Christophe

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