jscheme-user — list for general users

Re: [Jscheme-user] jscheme and oop

[Timothy H. <tim...@ma...>]

Hi Boris,

On Sunday, March 9, 2003, at 12:55 AM, Boris Tschirschwitz wrote:
> Hi.
>
> Assuming that my ignorance mostly stems from not having studied jscheme
> long enough, I checked the list archives for answers,
Thanks for checking first!

> but I couldn't find
> anything and the sf system seems to be really terrible.
What made it so horrible? Response time, organization,...?

>
> I am wondering about the following: If I want to program using classes 
> and
> objects, do I have to make all my structures Java classes, objects, ...?
> I wonder if this might restrict me in manipulating these objects in the
> scheme way. Yes, this sounds very vague, b/c I am not absolutely sure 
> what
> I am asking and hope that someone on the list might understand it better
> than I do.

You should look at the webpage:
       http://jscheme.sourceforge.net/jscheme/src/dclass/dclass.html
which describes several approaches for working with Java classes from 
Jscheme.

In summary, the main approaches we've tried are:
  * don't define any new classes (i.e. use Java as a library language), 
e.g. see the jlib/Swing.scm library
  * when this doesn't work, define a wrapper class that allows you to 
dynamically
     assign functionality to a Java class from Jscheme (e.g. see the 
jlib/SchemeCanvas.java class)
  * for an interface you can use the Proxy class to implement that 
interface at runtime in Jscheme
  * for a non-interface, you can use the dclass package to define Java 
classes in Scheme
     and compile them to Java, e.g. the weblink above gives an example of 
defining a class
     "Compare" in a package "frog". This example is in dclass/test.scm, 
reproduced below:
>
>   (define-class
>     (package frog)
>     (import java.util.Comparator)
>     (public class Compare implements Comparator)
>     ;; Design issue, fields must be public for Jscheme code to access.
>
>     (public Procedure predicate)	
>
>     (public Compare (Procedure predicate)
>      (.predicate$ this predicate))
>
>     (public boolean predicate (Object a Object b)
>      ((.predicate$ this) a b))
>
>     (public int compare (Object a Object b)
>      (cond ((.predicate this a b) -1)
> 	   ((.predicate this b a) 1)
> 	   (else 0)))
>
>     (public boolean equals (Object that)
>      (and (eq? (.getClass this) (.getClass that))
> 	  (eq? (.predicate$ this) (.predicate$ that))))
>
>     (public int hashCode () 0))
>
>


     The following script shows how to run that example:

> % java -cp lib/jscheme.jar:src jscheme.REPL
Note:  we have to add a folder "src" to the classpath as dclass will 
compile all new classes into
this folder..
>
>
> Jscheme 6.1.0 3/7/2003 http://jscheme.sourceforge.net
>
>
> > (load "elf/basic.scm")
> #t
> > (load "dclass/dclass.scm")
> #t
At this point we have loaded in the dclass compiler...
we are now ready to compile a new class, we could do this interactively
by making a call to   > (define-class (package-frog) ....)
But that can be error-prone...., so we load it in from a file....

> > (load "dclass/test.scm")
; the compiler echoes the generated code to the console as well as to 
the file
> Writing Java code for frog.Compare to 
> /Users/tim/Research/Software/jscheme/src/frog/Compare.java
> // Generated by Jscheme by tim  on Sun Mar 09 04:16:20 EST 2003
>  package frog;
> import java.util.Comparator;
> import jsint.Procedure;
> import jscheme.JS;
> public class Compare implements Comparator { public Procedure predicate;
> public Compare(Procedure predicate) { JS.call(DCLASS_C_Compare0, this, 
> predicate);
> }
> private static final Procedure DCLASS_C_Compare0 =(Procedure) 
> JS.eval("(lambda (this predicate) (.predicate$ this predicate))");
> public boolean predicate(Object a, Object b) { return 
> JS.booleanValue(JS.call(DCLASS_M_I_predicate1, this, a, b));
> }
> private static final Procedure DCLASS_M_I_predicate1 =(Procedure) 
> JS.eval("(lambda (this a b) ((.predicate$ this) a b))");
> public int compare(Object a, Object b) { return 
> JS.intValue(JS.call(DCLASS_M_I_compare2, this, a, b));
> }
> private static final Procedure DCLASS_M_I_compare2 =(Procedure) 
> JS.eval("(lambda (this a b) (cond ((.predicate this a b) -1) 
> ((.predicate this b a) 1) (else 0)))");
> public boolean equals(Object that) { return 
> JS.booleanValue(JS.call(DCLASS_M_I_equals3, this, that));
> }
> private static final Procedure DCLASS_M_I_equals3 =(Procedure) 
> JS.eval("(lambda (this that) (and (eq? (.getClass this) (.getClass 
> that)) (eq? (.predicate$ this) (.predicate$ that))))");
> public int hashCode() { return 
> JS.intValue(JS.call(DCLASS_M_I_hashCode4, this));
> }
> private static final Procedure DCLASS_M_I_hashCode4 =(Procedure) 
> JS.eval("(lambda (this) 0)");
> }
> Compiling Java code for frog.Compare
and it compiles the new code to src/from/Compare.class where it is 
immediately available to us
> #t
>
Next we use it to sort two arrays.... using two different comparators c1 
and c2
> > (define c (frog.Compare. <))
> frog.Compare@0
> > (define arr #(1 4 2 5 6 79 3 4 8 5 3))
> #(1 4 2 5 6 79 3 4 8 5 3)
> > (Arrays.sort arr c)
> #null
> > arr
> #(1 2 3 3 4 4 5 5 6 8 79)
>
> > (define c2 (frog.Compare. (lambda(x y) (or (< (first x) (first y)) (> 
> (second x) (second y))))))
.... this is a wierd sorting predicate, you can have A<B and B<A for 
certain lists A,B, e.g. (1 5) and (4 6)
> frog.Compare@0
> > (define arr2 #((1 5) (4 3) (4 6) (5 3) (1 3) (1 6) (5 3) (5 4)))
> #((1 5) (4 3) (4 6) (5 3) (1 3) (1 6) (5 3) (5 4))
> > (Arrays.sort arr2 c2)
> #null
> > arr2
> #((1 6) (1 5) (4 6) (1 3) (4 3) (5 4) (5 3) (5 3))
>
> > (exit)
> #t
> %
>

I hope this starts to answer your question...

> Would it be beneficial to use something like Meroon?
Perhaps, but then you may have to worry about interacting with two object
systems, Java's and Meroon's. I haven't tried to get Meroon working in
Jscheme and it might be interesting!

Best,
---Tim---

Re: [Jscheme-user] way to stop loading a file?

[Ken A. <kan...@bb...>]

I've been thinking about this too.  It's easy to get a runaway computation that you'd like to stop.

We could do that by checking for a stop flag that is checked at each procedure call. 

At 07:01 AM 3/9/2003 -0500, Geoffrey Knauth wrote:
>Let's say I'm in the middle of loading a file foo.scm.
>
>I get part of the way through the file, and then I realize some core data structures are messed up.  I want to signal an error and stop loading foo.scm, but I may not want to leave the JScheme interpreter.  
>Can I do that (leave foo.scm but not JScheme)?
>
>Geoffrey
>
>
>
>-------------------------------------------------------
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Re: [Jscheme-user] help features in JScheme

[Ken A. <kan...@bb...>]

> (apropos "file")
file: 
open-input-file: {jsint.Primitive open-input-file[1]}
open-output-file: {jsint.Primitive open-output-file[1]}
call-with-output-file: {jsint.Primitive call-with-output-file[2]}
call-with-input-file: {jsint.Primitive call-with-input-file[2]}
> (define (frogs n) (+ n 3))
{jsint.Closure frogs[1] (n)}
> (apropos "frogs")
frogs: {jsint.Closure frogs[1] (n)}

At 06:30 AM 3/9/2003 -0500, Geoffrey Knauth wrote:
>Something I like in JScheme:
>
>If I don't remember the arguments to a function, I can just type the name of an application's function:
>
>e.g., DEMAND_STREAMS_OF_TYPE
>
>and it will return the number and name of the expected arguments:
>
>e.g. ... Closure DEMAND_STREAMS_OF_TYPE[2] (type cs-descr)
>
>How much more would it take to adopt an Emacs-like standard of having an optional initial string representing help text?  If the string were a URL, it also could point to online help with markup, while keeping clutter in a user's Scheme code to a minimum.  If the URL used quasiquotes, you could have the online help toggle between the JScheme website for core JScheme functions, and a local site when the JScheme user is offline or for help with the JScheme user's own application code.
>
>Geoffrey
>
>
>
>-------------------------------------------------------
>This SF.net email is sponsored by: Etnus, makers of TotalView, The debugger for complex code. Debugging C/C++ programs can leave you feeling lost and disoriented. TotalView can help you find your way. Available on major UNIX and Linux platforms. Try it free. www.etnus.com
>_______________________________________________
>Jscheme-user mailing list
>Jsc...@li...
>https://lists.sourceforge.net/lists/listinfo/jscheme-user

Fwd: [Jscheme-user] jscheme and oop

[Timothy H. <tim...@ma...>]

> Hi Boris,
>
> On Sunday, March 9, 2003, at 12:55 AM, Boris Tschirschwitz wrote:
>> Hi.
>>
>> Assuming that my ignorance mostly stems from not having studied jscheme
>> long enough, I checked the list archives for answers,
> Thanks for checking first!
>
>> but I couldn't find
>> anything and the sf system seems to be really terrible.
> What made it so horrible? Response time, organization,...?
>
>>
>> I am wondering about the following: If I want to program using classes 
>> and
>> objects, do I have to make all my structures Java classes, 
>> objects, ...?
>> I wonder if this might restrict me in manipulating these objects in the
>> scheme way. Yes, this sounds very vague, b/c I am not absolutely sure 
>> what
>> I am asking and hope that someone on the list might understand it 
>> better
>> than I do.
>
> You should look at the webpage:
>       http://jscheme.sourceforge.net/jscheme/src/dclass/dclass.html
> which describes several approaches for working with Java classes from 
> Jscheme.
>
> In summary, the main approaches we've tried are:
>  * don't define any new classes (i.e. use Java as a library language), 
> e.g. see the jlib/Swing.scm library
>  * when this doesn't work, define a wrapper class that allows you to 
> dynamically
>     assign functionality to a Java class from Jscheme (e.g. see the 
> jlib/SchemeCanvas.java class)
>  * for an interface you can use the Proxy class to implement that 
> interface at runtime in Jscheme
>  * for a non-interface, you can use the dclass package to define Java 
> classes in Scheme
>     and compile them to Java, e.g. the weblink above gives an example 
> of defining a class
>     "Compare" in a package "frog". This example is in dclass/test.scm, 
> reproduced below:
>>
>>   (define-class
>>     (package frog)
>>     (import java.util.Comparator)
>>     (public class Compare implements Comparator)
>>     ;; Design issue, fields must be public for Jscheme code to access.
>>
>>     (public Procedure predicate)	
>>
>>     (public Compare (Procedure predicate)
>>      (.predicate$ this predicate))
>>
>>     (public boolean predicate (Object a Object b)
>>      ((.predicate$ this) a b))
>>
>>     (public int compare (Object a Object b)
>>      (cond ((.predicate this a b) -1)
>> 	   ((.predicate this b a) 1)
>> 	   (else 0)))
>>
>>     (public boolean equals (Object that)
>>      (and (eq? (.getClass this) (.getClass that))
>> 	  (eq? (.predicate$ this) (.predicate$ that))))
>>
>>     (public int hashCode () 0))
>>
>>
>
>
>     The following script shows how to run that example:
>
>> % java -cp lib/jscheme.jar:src jscheme.REPL
> Note:  we have to add a folder "src" to the classpath as dclass will 
> compile all new classes into
> this folder..
>>
>>
>> Jscheme 6.1.0 3/7/2003 http://jscheme.sourceforge.net
>>
>>
>> > (load "elf/basic.scm")
>> #t
>> > (load "dclass/dclass.scm")
>> #t
> At this point we have loaded in the dclass compiler...
> we are now ready to compile a new class, we could do this interactively
> by making a call to   > (define-class (package-frog) ....)
> But that can be error-prone...., so we load it in from a file....
>
>> > (load "dclass/test.scm")
> ; the compiler echoes the generated code to the console as well as to 
> the file
>> Writing Java code for frog.Compare to 
>> /Users/tim/Research/Software/jscheme/src/frog/Compare.java
>> // Generated by Jscheme by tim  on Sun Mar 09 04:16:20 EST 2003
>>  package frog;
>> import java.util.Comparator;
>> import jsint.Procedure;
>> import jscheme.JS;
>> public class Compare implements Comparator { public Procedure 
>> predicate;
>> public Compare(Procedure predicate) { JS.call(DCLASS_C_Compare0, this, 
>> predicate);
>> }
>> private static final Procedure DCLASS_C_Compare0 =(Procedure) 
>> JS.eval("(lambda (this predicate) (.predicate$ this predicate))");
>> public boolean predicate(Object a, Object b) { return 
>> JS.booleanValue(JS.call(DCLASS_M_I_predicate1, this, a, b));
>> }
>> private static final Procedure DCLASS_M_I_predicate1 =(Procedure) 
>> JS.eval("(lambda (this a b) ((.predicate$ this) a b))");
>> public int compare(Object a, Object b) { return 
>> JS.intValue(JS.call(DCLASS_M_I_compare2, this, a, b));
>> }
>> private static final Procedure DCLASS_M_I_compare2 =(Procedure) 
>> JS.eval("(lambda (this a b) (cond ((.predicate this a b) -1) 
>> ((.predicate this b a) 1) (else 0)))");
>> public boolean equals(Object that) { return 
>> JS.booleanValue(JS.call(DCLASS_M_I_equals3, this, that));
>> }
>> private static final Procedure DCLASS_M_I_equals3 =(Procedure) 
>> JS.eval("(lambda (this that) (and (eq? (.getClass this) (.getClass 
>> that)) (eq? (.predicate$ this) (.predicate$ that))))");
>> public int hashCode() { return 
>> JS.intValue(JS.call(DCLASS_M_I_hashCode4, this));
>> }
>> private static final Procedure DCLASS_M_I_hashCode4 =(Procedure) 
>> JS.eval("(lambda (this) 0)");
>> }
>> Compiling Java code for frog.Compare
> and it compiles the new code to src/from/Compare.class where it is 
> immediately available to us
>> #t
>>
> Next we use it to sort two arrays.... using two different comparators 
> c1 and c2
>> > (define c (frog.Compare. <))
>> frog.Compare@0
>> > (define arr #(1 4 2 5 6 79 3 4 8 5 3))
>> #(1 4 2 5 6 79 3 4 8 5 3)
>> > (Arrays.sort arr c)
>> #null
>> > arr
>> #(1 2 3 3 4 4 5 5 6 8 79)
>>
>> > (define c2 (frog.Compare. (lambda(x y) (or (< (first x) (first 
>> y)) (> (second x) (second y))))))
> .... this is a wierd sorting predicate, you can have A<B and B<A for 
> certain lists A,B, e.g. (1 5) and (4 6)
>> frog.Compare@0
>> > (define arr2 #((1 5) (4 3) (4 6) (5 3) (1 3) (1 6) (5 3) (5 4)))
>> #((1 5) (4 3) (4 6) (5 3) (1 3) (1 6) (5 3) (5 4))
>> > (Arrays.sort arr2 c2)
>> #null
>> > arr2
>> #((1 6) (1 5) (4 6) (1 3) (4 3) (5 4) (5 3) (5 3))
>>
>> > (exit)
>> #t
>> %
>>
>
> I hope this starts to answer your question...
>
>> Would it be beneficial to use something like Meroon?
> Perhaps, but then you may have to worry about interacting with two 
> object
> systems, Java's and Meroon's. I haven't tried to get Meroon working in
> Jscheme and it might be interesting!
>
> Best,
> ---Tim---
>

Re: [Jscheme-user] jscheme and oop

[Ken A. <kan...@bb...>]

We have not developed an object system for JScheme, however you can define Java classes in JScheme, see http://jscheme.sourceforge.net/jscheme/src/dclass/dclass.html for several ways.
There is also http://jscheme.sourceforge.net/jscheme/src/dclass/record.scm
for defining simple record structures more easily than using define-class directly.

You can also define common lisp like methods. see 
http://jscheme.sourceforge.net/jscheme/src/elf/iterate.scm

I do have a simple prototype based system that i use.  I may check it is as an example.

One of the main issues of an Object System for JScheme is how it would interact with Java classes. 

At 09:55 PM 3/8/2003 -0800, Boris Tschirschwitz wrote:
>Hi.
>
>Assuming that my ignorance mostly stems from not having studied jscheme
>long enough, I checked the list archives for answers, but I couldn't find
>anything and the sf system seems to be really terrible.
>
>I am wondering about the following: If I want to program using classes and
>objects, do I have to make all my structures Java classes, objects, ...?
>I wonder if this might restrict me in manipulating these objects in the
>scheme way. Yes, this sounds very vague, b/c I am not absolutely sure what
>I am asking and hope that someone on the list might understand it better
>than I do.
>Would it be beneficial to use something like Meroon?
>
>Boris.
>
>
>
>
>
>-------------------------------------------------------
>This SF.net email is sponsored by: Etnus, makers of TotalView, The debugger 
>for complex code. Debugging C/C++ programs can leave you feeling lost and 
>disoriented. TotalView can help you find your way. Available on major UNIX 
>and Linux platforms. Try it free. www.etnus.com
>_______________________________________________
>Jscheme-user mailing list
>Jsc...@li...
>https://lists.sourceforge.net/lists/listinfo/jscheme-user

[Jscheme-user] way to stop loading a file?

[Geoffrey K. <ge...@kn...>]

Let's say I'm in the middle of loading a file foo.scm.

I get part of the way through the file, and then I realize some core 
data structures are messed up.  I want to signal an error and stop 
loading foo.scm, but I may not want to leave the JScheme interpreter.  
Can I do that (leave foo.scm but not JScheme)?

Geoffrey

[Jscheme-user] help features in JScheme

[Geoffrey K. <ge...@kn...>]

Something I like in JScheme:

If I don't remember the arguments to a function, I can just type the 
name of an application's function:

e.g., DEMAND_STREAMS_OF_TYPE

and it will return the number and name of the expected arguments:

e.g. ... Closure DEMAND_STREAMS_OF_TYPE[2] (type cs-descr)

How much more would it take to adopt an Emacs-like standard of having 
an optional initial string representing help text?  If the string were 
a URL, it also could point to online help with markup, while keeping 
clutter in a user's Scheme code to a minimum.  If the URL used 
quasiquotes, you could have the online help toggle between the JScheme 
website for core JScheme functions, and a local site when the JScheme 
user is offline or for help with the JScheme user's own application 
code.

Geoffrey

[Jscheme-user] jscheme and oop

[Boris T. <bo...@ma...>]

Hi.

Assuming that my ignorance mostly stems from not having studied jscheme
long enough, I checked the list archives for answers, but I couldn't find
anything and the sf system seems to be really terrible.

I am wondering about the following: If I want to program using classes and
objects, do I have to make all my structures Java classes, objects, ...?
I wonder if this might restrict me in manipulating these objects in the
scheme way. Yes, this sounds very vague, b/c I am not absolutely sure what
I am asking and hope that someone on the list might understand it better
than I do.
Would it be beneficial to use something like Meroon?

Boris.

[Jscheme-user] Fwd: Re: Y Store /Closures

[Ken A. <kan...@bb...>]

This is from light weight languages.
We should check out how SISC does continuations.

>To: Daniel Weinreb <DLW...@at...>
>Cc: Christopher Barber <cb...@cu...>,
>   Sundar Narasimhan <su...@as...>, mv...@cs...,
>   eli...@ve..., ll1...@ai...
>Subject: Re: Y Store /Closures
>From: Matthias Radestock <mat...@so...>
>Date: 08 Mar 2003 13:47:34 +0000
>Lines: 44
>User-Agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.4 (Portable Code)
>Sender: own...@ai...
>Old-X-Spam-Status: NO
>Old-X-Scanned-By: MIMEDefang 2.28 (www . roaringpenguin . com / mimedefang)
>Old-X-Scanned-By: MIMEDefang 2.17 (www . roaringpenguin . com / mimedefang)
>X-Scanned-By: Spam Assassin
>X-Spam-Status: No, hits=-3.4 required=5.0
>        tests=IN_REP_TO
>        version=2.31
>X-Spam-Level: 
>
>Daniel Weinreb <DLW...@at...> writes:
>
>> Now, here's what I want to know. Suppose you want to write a web
>> app that maintains state between clicks in the fashion I've been describing,
>> but you don't want all that state to be lost in case there is a reboot or
>> power failure or crash. In the event-driven style, the state can be stored
>> persistently, in a file or database system, so that when the next HTTP
>> request comes along, you can pick up where you left off, but in a
>> conventional
>> language-with-continuations scenario, the continuation state is all in
>> virtual
>> memory and lost when there's a crash.  What can anyone recommend?
>
>When writing continuation-based web apps using the SISC Scheme
>interpreter (http://sisc.sourceforge.net) continuations get stored in
>the user session of the J2EE app server. SISC continuations are
>java-serializable. Many app servers deal with session migration by
>serializing the sessions and restoring them on the migration
>target. Persistence is accomplished by simply storing the serialized
>continuations in a DB. I have run experiments with Tomcat involving the
>restarting of the app server in the middle of a workflow - it all works
>beautifully.
>
>As has been pointed out elsewhere, one needs to be careful about
>ensuring that cntinuations do not hang on to unnecessary state,
>particularly state that is not serializable. Some J2EE objects, such as
>http requests are not serializable and are quite prone to ending up in
>the continuation, thus breaking serialization. In my SISC web apps I
>get around this through some scaffolding that involves storing these
>transient objects in what amounts to thread-locals. This happens
>transparently to application code.
>
>Continuations in a user session tend to share a lot of state. So the
>storage requirement and (de)serialization runtime cost is actually quite
>low for all continuations except the first. Also, serialization of
>continuations in SISC never serializes the top-level, i.e. "global"
>state, since that would entail serializing pretty much the entire heap
>and hence be way too expensive. This, of course, means that application
>state should not be stored in the top-level if it is to be
>persistent. That's ok though since in most apps the application state is
>kept in the DB / some remote EJBs anyway.
>
>
>Matthias.

Re: [Jscheme-user] Minor nuisance/inconsistency

[Robert J. B. <ru...@bb...>]

Tim,
I am comfortable with second and third showing an error -- their 
intended semantics is to treat the sequence of linked pairs as a linear 
structure and get the numbered element. It is an "implementation detail" 
that second is the same as cadr. I also support having symbolic methods 
fourth, ... tenth -- I keep getting burned by their absense.
Thanks,
Rusty


Timothy Hickey wrote:

>
> On Friday, March 7, 2003, at 11:20 AM, Robert J. Bobrow wrote:
>
>> Folks,
>> I  would expect that (cadr x) and (car (cdr x)) would behave 
>> identically in all circumstances. Yet I find that car and cdr behave 
>> like Common Lisp and return '() when given '() as an argument (I like 
>> this, personnaly) and cadr throws an exception when handed '();
>>
>> I think the inconsistency is annoying -- I really prefer not to have 
>> (car (cdr x)) in my code.
>
> I've fixed that inconsistency, cadr and caddr were treated differently 
> from all other cadadars
>
> I have however kept that behavior for second and third.
> So (second '(a)) --> error
>       (cadr '(a)) --> ()
> Perhaps it would be better to have second and third adhere to the same 
> semantics of cadr and caddr,
> but in a way it makes sense for second/third to give errors if the 
> lists are too short....
> I'd also like to add third, fourth, fifth, .... up to tenth or so....
>
> What do you think?
> ---Tim---
>
>

Re: [Jscheme-user] Re: modules?

[Timothy H. <tim...@ma...>]

On Friday, March 7, 2003, at 11:35 AM, Timothy Hickey wrote:
> We could easily write a little macro which implements this style
> of export:
>
>>   (export (future future? ...)
>>     (define (future x) ...)
>>     (define (future? x) ...)
>>     ...
>>   )
>>
>

;; Here is a version of the macro that implements "export"
;; I create the "bigsym" symbol to strictly include all other symbols
;; and hence be different from them, kind of a gensym....

(define (export Symbols . Body)
   ; this bigsymbol is guaranteed to be different from all individual 
symbols
   (define bigsym (string->symbol (apply string-append (cons "R_" (map 
.toString Symbols)))))
   (define (make-defines N S)
      (if (null? S) ()
          (cons `(set! ,(first S) (list-ref ,bigsym ,N))
                 (make-defines (+ N 1) (rest S)))))
   `((lambda (,bigsym)
        ,@(make-defines 0 Symbols))
     (let () ,@Body ,(cons 'list Symbols))
    ))

e.g.

(export '(R S) (set! R 1) (set! S 2))

  -->

(  (lambda (R_RS)
          (set! R (list-ref R_RS 0))
          (set! S (list-ref R_RS 1)))

     (let () 1 2 (list R S))
)

Oh... but this will still have problems if list-ref is one of the symbols
being exported.... This is why hygeniec macros are nice....

---Tim---



>
> Similarly, we could wriite a macro to import just a few values from a 
> file
>> (import "elf/future.scm" (future future?  ...))
>
> which could expand to
>>  (import "elf/future.scm" "HIDDEN:")
>>  (define future HIDDEN:future)
>>  (define future? HIDDEN:future?)
>>  ...
>
> Other variations could be implemented as well (import-all-but ....) etc.
>
> ---Tim---
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
> debugger for complex code. Debugging C/C++ programs can leave you 
> feeling lost and disoriented. TotalView can help you find your way. 
> Available on major UNIX and Linux platforms. Try it free. www.etnus.com
> _______________________________________________
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> Jsc...@li...
> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>

Re: [Jscheme-user] Minor nuisance/inconsistency

[Timothy H. <tim...@ma...>]

On Friday, March 7, 2003, at 11:20 AM, Robert J. Bobrow wrote:

> Folks,
> I  would expect that (cadr x) and (car (cdr x)) would behave 
> identically in all circumstances. Yet I find that car and cdr behave 
> like Common Lisp and return '() when given '() as an argument (I like 
> this, personnaly) and cadr throws an exception when handed '();
>
> I think the inconsistency is annoying -- I really prefer not to have 
> (car (cdr x)) in my code.
I've fixed that inconsistency, cadr and caddr were treated differently 
from all other cadadars

I have however kept that behavior for second and third.
So (second '(a)) --> error
       (cadr '(a)) --> ()
Perhaps it would be better to have second and third adhere to the same 
semantics of cadr and caddr,
but in a way it makes sense for second/third to give errors if the lists 
are too short....
I'd also like to add third, fourth, fifth, .... up to tenth or so....

What do you think?
---Tim---

Re: [Jscheme-user] Minor nuisance/inconsistency

[Geoffrey K. <ge...@kn...>]

I ran into something similar this morning.  Both (car ()) and (cdr ()) 
returned (), while according to MIT Scheme, which I use for reference, 
feeding () to either car or cdr was a no-no.  In the case of car, I 
knew that.  In the case of cdr, I had to remember that (cdr ()) was OK 
in Lisp but not in Scheme.

Like Rusty, I don't mind that (cdr ()) returns (), but I have a small 
problem.  I have some expressions to debug that look like (caar (cddr 
X)) that I'm trying to debug by taking them apart (car (car (cdr (cdr 
X)))), and I'm getting exceptions in the former but not in the latter.

Geoffrey

On Friday, March 7, 2003, at 11:20 AM, Robert J. Bobrow wrote:

> Folks,
> I  would expect that (cadr x) and (car (cdr x)) would behave 
> identically in all circumstances. Yet I find that car and cdr behave 
> like Common Lisp and return '() when given '() as an argument (I like 
> this, personnaly) and cadr throws an exception when handed '();
>
> I think the inconsistency is annoying -- I really prefer not to have 
> (car (cdr x)) in my code.
>
> Any recommendations?
> --Rusty Bobrow

[Jscheme-user] Re: modules?

[Timothy H. <tim...@ma...>]

On Friday, March 7, 2003, at 11:15 AM, Ken Anderson wrote:

> Some questions about modules.
>
> ? is there a way to export symbols?
Currently, everything is exported....
>  For example, in the elf/future.scm i wanted to export future, future?, 
> determined?, touch, and i wanted to have the other procedures not show 
> up in the user's environment.
>
> Rather than loading a module and seeing the exported symbols, i have to 
> explictly import it with a prefix say, "f:".
or you can import everything without a prefix ...
>  Then i either have to say
> (f:future x) or
> (define future f:future)
The current implementation allows either a prefixed importation
(environment-import "abc.scm" "f:")
or a non-prefixed import
(environment-import "abc.scm")
There is currently no way to import only a selected subset
or to export a selected subset...

Actually, you can "hack" export using set!,
The set! makes the assignment occur in the toplevel
environment and the (let () ...) hides all the other
assignments ...

> (
>   (let ()    ;;; define future, future? etc inside a let() environment
>     (define (future x) ...)
>     (define (future? x) ...)
>      ...
>     (list future future? ...))
>
>   (lambda R  ;;; use set! to lift these definitions to the global 
> environment
>     (set! future (first R))
>     (set! future? (second R))
>     ...)
> )

We could easily write a little macro which implements this style
of export:

>   (export (future future? ...)
>     (define (future x) ...)
>     (define (future? x) ...)
>     ...
>   )
>


Similarly, we could wriite a macro to import just a few values from a 
file
> (import "elf/future.scm" (future future?  ...))

which could expand to
>  (import "elf/future.scm" "HIDDEN:")
>  (define future HIDDEN:future)
>  (define future? HIDDEN:future?)
>  ...

Other variations could be implemented as well (import-all-but ....) etc.

---Tim---

[Jscheme-user] Minor nuisance/inconsistency

[Robert J. B. <ru...@bb...>]

Folks,
I  would expect that (cadr x) and (car (cdr x)) would behave identically 
in all circumstances. Yet I find that car and cdr behave like Common 
Lisp and return '() when given '() as an argument (I like this, 
personnaly) and cadr throws an exception when handed '();

I think the inconsistency is annoying -- I really prefer not to have 
(car (cdr x)) in my code.

Any recommendations?
--Rusty Bobrow

[Jscheme-user] modules?

[Ken A. <kan...@bb...>]

Some questions about modules.

? is there a way to export symbols?  For example, in the elf/future.scm i wanted to export future, future?, determined?, touch, and i wanted to have the other procedures not show up in the user's environment.

Rather than loading a module and seeing the exported symbols, i have to explictly import it with a prefix say, "f:".  Then i either have to say
(f:future x) or
(define future f:future)

This doesn't seem right.

Re: [Jscheme-user] synchronized?

[Ken A. <kan...@bb...>]

At 04:05 PM 3/5/2003 -0500, Geoffrey Knauth wrote:
>Tim, thanks for those code examples.  I'll keep them for any possible Swing work with threads.
>
>However the true motivation for the question had to do with launching a few separate processing tasks in their own threads.  For example, processes A1 and A2 are prerequisites for B, and we are just wondering if, in staying with JScheme, we might be able to get A1 and A2 to happen more in parallel.  It's nice to know we can.

This reminded me of a future implementation i just checked in in elf/future.scm
(future expression) evaluates expression in a separate thread and returns a future which can be touched to get the value of the future, suspending if it's value isn't available yet.  So you have one object that gives you parallelism and syncronization. 

[Jscheme-user] SaxExp.scm

[<da...@da...>]

I jave been playing around  SaxExp.scm using java1.4.
It appears that it is supposed to ignore newlines  in elements,
but i keep getting stuff like this: 

(vienna "\n  " (options "\n    " (savepassword "true") (maxrows "500") .....

from this 

<vienna>
  <options>
    <savepassword>true</savepassword>
    <maxrows>500</maxrows>
    <tablefont>
      <family>dialog</family>
      <style>plain</style>
      <size>12</size>
    </tablefont>
..
..

do I need to clean the newlines from the xml before I parse it?


BTW I set  

(System.setProperty "org.xml.sax.driver"
		       "org.apache.crimson.parser.XMLReaderImpl")
   )
in the SaxExp.scm code before compiling


thanks
davud

Re: [Jscheme-user] synchronized?

[Geoffrey K. <ge...@kn...>]

Tim, thanks for those code examples.  I'll keep them for any possible 
Swing work with threads.

However the true motivation for the question had to do with launching a 
few separate processing tasks in their own threads.  For example, 
processes A1 and A2 are prerequisites for B, and we are just wondering 
if, in staying with JScheme, we might be able to get A1 and A2 to 
happen more in parallel.  It's nice to know we can.

Geoffrey

On Wednesday, March 5, 2003, at 03:56 PM, Timothy Hickey wrote:

> If you are going to start working with Threads and JScheme you might 
> want to
> be careful when working with Swing GUIs. Swing is not thread safe so 
> it is a
> good idea to execute any GUI manipulations in the AWT event queue 
> thread.
> This is done by using
>>   (javax.swing.SwingUtilities.invokeAndWait (lambda() ...code to be 
>> executed...))
>> or
>>   (javax.swing.SwingUtilities.invokeLater (lambda() ...code to be 
>> executed...))
> They both add the code to the event Queue as a runnable, this should 
> only be done
> from calls that are forked off of the main thread....
>
> I usually also wrap the code in a tryCatch so as to catch any errors 
> that might occur.
> Otherwise the errors cause the thread to halt but are otherwise not 
> observable:
>
>> (define(invokeAndWait F)
>>      (javax.swing.SwingUtilities.invokeAndWait (lambda()
>>          (tryCatch
>>              (F)
>>              (lambda(e) (printdebug 'error {ERROR in invokeAndWait: 
>> [F], [e]\n})))
>>      ))
>>   )
>> ;; where printdebug is the  error printing procedure for your 
>> application....
>>
>
>
> Have fun,
> and be careful out there!
> ---Tim---
>
>
> On Wednesday, March 5, 2003, at 03:46 PM, Geoffrey Knauth wrote:
>
>> Thanks Tim!  Just what the doctor ordered.  --Geoffrey
>>
>> On Wednesday, March 5, 2003, at 03:24 PM, Timothy Hickey wrote:
>>
>>> (synchronize X F)
>>> synchronizes the current thread on object X and blocks until it gets 
>>> the
>>> lock on X, at which time it calls (F X)
>>>
>>> e.g.
>>> (synchronize x .wait) gets a lock on x and then gives up all locks 
>>> and waits until it is notified
>>> (synchronize x .notify) gets a lock on x and then notifies some 
>>> thread waiting on x
>>>
>>> I often use the idiom
>>>   (synchronize g (lambda(g) ....))
>>> or
>>>   (synchronize g (lambda(_) ...))
>>>
>>> ---Tim---
>>>
>>> On Wednesday, March 5, 2003, at 01:58 PM, Geoffrey Knauth wrote:
>>>
>>>> I can use Java threads from JScheme.
>>>>
>>>> But can I make JScheme variables `synchronized' ?
>>>>
>>>> Geoffrey
>>>>
>>>>
>>>>
>>>> -------------------------------------------------------
>>>> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
>>>> debugger for complex code. Debugging C/C++ programs can leave you 
>>>> feeling lost and disoriented. TotalView can help you find your way. 
>>>> Available on major UNIX and Linux platforms. Try it free. 
>>>> www.etnus.com
>>>> _______________________________________________
>>>> Jscheme-user mailing list
>>>> Jsc...@li...
>>>> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>>>>
>>>
>>
>>
>>
>> -------------------------------------------------------
>> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
>> debugger for complex code. Debugging C/C++ programs can leave you 
>> feeling lost and disoriented. TotalView can help you find your way. 
>> Available on major UNIX and Linux platforms. Try it free. 
>> www.etnus.com
>> _______________________________________________
>> Jscheme-user mailing list
>> Jsc...@li...
>> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>>
>

Re: [Jscheme-user] synchronized?

[Timothy H. <tim...@ma...>]

If you are going to start working with Threads and JScheme you might 
want to
be careful when working with Swing GUIs. Swing is not thread safe so it 
is a
good idea to execute any GUI manipulations in the AWT event queue thread.
This is done by using
>   (javax.swing.SwingUtilities.invokeAndWait (lambda() ...code to be 
> executed...))
> or
>   (javax.swing.SwingUtilities.invokeLater (lambda() ...code to be 
> executed...))
They both add the code to the event Queue as a runnable, this should 
only be done
from calls that are forked off of the main thread....

I usually also wrap the code in a tryCatch so as to catch any errors 
that might occur.
Otherwise the errors cause the thread to halt but are otherwise not 
observable:

> (define(invokeAndWait F)
>      (javax.swing.SwingUtilities.invokeAndWait (lambda()
>          (tryCatch
>              (F)
>              (lambda(e) (printdebug 'error {ERROR in invokeAndWait: 
> [F], [e]\n})))
>      ))
>   )
> ;; where printdebug is the  error printing procedure for your 
> application....
>


Have fun,
and be careful out there!
---Tim---


On Wednesday, March 5, 2003, at 03:46 PM, Geoffrey Knauth wrote:

> Thanks Tim!  Just what the doctor ordered.  --Geoffrey
>
> On Wednesday, March 5, 2003, at 03:24 PM, Timothy Hickey wrote:
>
>> (synchronize X F)
>> synchronizes the current thread on object X and blocks until it gets 
>> the
>> lock on X, at which time it calls (F X)
>>
>> e.g.
>> (synchronize x .wait) gets a lock on x and then gives up all locks and 
>> waits until it is notified
>> (synchronize x .notify) gets a lock on x and then notifies some thread 
>> waiting on x
>>
>> I often use the idiom
>>   (synchronize g (lambda(g) ....))
>> or
>>   (synchronize g (lambda(_) ...))
>>
>> ---Tim---
>>
>> On Wednesday, March 5, 2003, at 01:58 PM, Geoffrey Knauth wrote:
>>
>>> I can use Java threads from JScheme.
>>>
>>> But can I make JScheme variables `synchronized' ?
>>>
>>> Geoffrey
>>>
>>>
>>>
>>> -------------------------------------------------------
>>> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
>>> debugger for complex code. Debugging C/C++ programs can leave you 
>>> feeling lost and disoriented. TotalView can help you find your way. 
>>> Available on major UNIX and Linux platforms. Try it free. 
>>> www.etnus.com
>>> _______________________________________________
>>> Jscheme-user mailing list
>>> Jsc...@li...
>>> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>>>
>>
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
> debugger for complex code. Debugging C/C++ programs can leave you 
> feeling lost and disoriented. TotalView can help you find your way. 
> Available on major UNIX and Linux platforms. Try it free. www.etnus.com
> _______________________________________________
> Jscheme-user mailing list
> Jsc...@li...
> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>

Re: [Jscheme-user] synchronized?

[Geoffrey K. <ge...@kn...>]

Thanks Tim!  Just what the doctor ordered.  --Geoffrey

On Wednesday, March 5, 2003, at 03:24 PM, Timothy Hickey wrote:

> (synchronize X F)
> synchronizes the current thread on object X and blocks until it gets 
> the
> lock on X, at which time it calls (F X)
>
> e.g.
> (synchronize x .wait) gets a lock on x and then gives up all locks and 
> waits until it is notified
> (synchronize x .notify) gets a lock on x and then notifies some thread 
> waiting on x
>
> I often use the idiom
>   (synchronize g (lambda(g) ....))
> or
>   (synchronize g (lambda(_) ...))
>
> ---Tim---
>
> On Wednesday, March 5, 2003, at 01:58 PM, Geoffrey Knauth wrote:
>
>> I can use Java threads from JScheme.
>>
>> But can I make JScheme variables `synchronized' ?
>>
>> Geoffrey
>>
>>
>>
>> -------------------------------------------------------
>> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
>> debugger for complex code. Debugging C/C++ programs can leave you 
>> feeling lost and disoriented. TotalView can help you find your way. 
>> Available on major UNIX and Linux platforms. Try it free. 
>> www.etnus.com
>> _______________________________________________
>> Jscheme-user mailing list
>> Jsc...@li...
>> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>>
>

Re: [Jscheme-user] synchronized?

[Timothy H. <tim...@ma...>]

(synchronize X F)
synchronizes the current thread on object X and blocks until it gets the
lock on X, at which time it calls (F X)

e.g.
(synchronize x .wait) gets a lock on x and then gives up all locks and 
waits until it is notified
(synchronize x .notify) gets a lock on x and then notifies some thread 
waiting on x

I often use the idiom
   (synchronize g (lambda(g) ....))
or
   (synchronize g (lambda(_) ...))

---Tim---

On Wednesday, March 5, 2003, at 01:58 PM, Geoffrey Knauth wrote:

> I can use Java threads from JScheme.
>
> But can I make JScheme variables `synchronized' ?
>
> Geoffrey
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
> debugger for complex code. Debugging C/C++ programs can leave you 
> feeling lost and disoriented. TotalView can help you find your way. 
> Available on major UNIX and Linux platforms. Try it free. www.etnus.com
> _______________________________________________
> Jscheme-user mailing list
> Jsc...@li...
> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>

[Jscheme-user] synchronized?

[Geoffrey K. <ge...@kn...>]

I can use Java threads from JScheme.

But can I make JScheme variables `synchronized' ?

Geoffrey

Re: [Jscheme-user] Re: jscheme and eclipse

[Timothy H. <tim...@ma...>]

On Tuesday, March 4, 2003, at 05:23 PM, Ken Anderson wrote:

> I don't believe anyone has yet, though it has been suggested.
> If you know how to do Eclipse plugin's maybe we can wipe up something 
> together.  I have not tried Eclipse yet.
I've forwarded this to someone in my group that works with Eclipse. He 
might have
a plug-in for Eclipse already... I let you know what he says.

---Tim---

>
> k
> At 01:27 PM 3/4/2003 -0800, Boris Tschirschwitz wrote:
>> Hello and sorry for polluting your inbox.
>>
>> Do you know if anyone has written an eclipse plugin for jscheme, yet.
>> Sorry, I ask b/c I'd like to use one, not write one.
>>
>> Thanks,
>> Boris.
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Etnus, makers of TotalView, The 
> debugger
> for complex code. Debugging C/C++ programs can leave you feeling lost 
> and
> disoriented. TotalView can help you find your way. Available on major 
> UNIX
> and Linux platforms. Try it free. www.etnus.com
> _______________________________________________
> Jscheme-user mailing list
> Jsc...@li...
> https://lists.sourceforge.net/lists/listinfo/jscheme-user
>

[Jscheme-user] Re: jscheme and eclipse

[Ken A. <kan...@bb...>]

I don't believe anyone has yet, though it has been suggested.
If you know how to do Eclipse plugin's maybe we can wipe up something together.  I have not tried Eclipse yet.

k
At 01:27 PM 3/4/2003 -0800, Boris Tschirschwitz wrote:
>Hello and sorry for polluting your inbox.
>
>Do you know if anyone has written an eclipse plugin for jscheme, yet.
>Sorry, I ask b/c I'd like to use one, not write one.
>
>Thanks,
>Boris.