Xotcl

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653 discussions

Filter Chaining Question
by Sheik Yussuff 16 Jul '01

16 Jul '01

Subject: The Adapter pattern inplemented with filters(code from distribution) The code below from the XOTcl distribution is given below. Suppose the class Adapter has another filter "filter2" registered after the filter "adapterFilter". My understanding of the code(below) is that only requests that are not found in specificRequest will be filtered by filter2. ......................................................... Question: If my understanding is correct, how can I have all messages/requests to Adapter be filtered by both filters. ......................................................... Code from distribution: Class Adapter -superclass Class Adapter metadata add description Adapter metadata description { Simple adapter pattern meta-class taken from the paper 'Filters as a Language Support for Design Patterns in Object-Oriented Scripting Languages'. } Adapter instproc adapterFilter args { # Appears that filter args == args of triggering method set r [self calledproc] [self] instvar specificRequest adaptee #puts [self] if {[info exists specificRequest($r)]} { #puts $args return [eval $adaptee $specificRequest($r) $args] } next } Adapter instproc init args { [self] filterappend [self class]::adapterFilter next [self] instproc setRequest {r sr} { [self] set specificRequest($r) $sr } [self] instproc setAdaptee {a} { [self] set adaptee $a } }

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patch release 2 of XOTcl 0.85
by Gustaf Neumann 13 Jul '01

13 Jul '01

Dear XOTcl community, on www.xotcl.org, you will find a patch release p2 of xotcl 0.85. The main fixes are: - propagation of special return codes (e.g. ... return -code continue ...) which is needed for Tk event maps, as catherine pointed out - first version of custom setter/getter methods for -parameter (see for now: apps/scripts/parameter.xotcl) The documented part in parameter.xotcl is intended to stay, some more features might be added. Preview for the next major release: Uwe has rewritten a good deal of the filters/mixins code, which is running through our regression test already. Among other things, this will introduce per object filters; this will complete our matrix of orthogonal features below: per object per class filter filter instfilter mixin mixin instmixin This is, however, a major change in the code, it will require some more testing etc, and it will go into the next major release. best regards -gustaf neumann

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"Simple Delegation" revisited (long post)
by Sheik Yussuff 13 Jul '01

13 Jul '01

Just over 6 months ago,Catherine Letondal raised the issue of implementing "simple delegation". Professor G. Neumann replied with some code showing how it can be done as well as suggesting that one may use a filter to filter all methods or an instmixin to target specific methods for delegation. I am now learning Tcl and XOTcl (a week or so now)at the same time and have decided to try the filter approach. The Experiment: 1. Create a meta-class SimpleDelegation 2. add a filter sdFilter to this meta-class 3. add an instproc setDelegate 4. Create classes A and B using SimpleDelegate 5. Create class C using Class 6. A has as delegate(instvar) an object of class B; B has as delegate an object of class C 7. A,B and C has a method "m" defined The Problem: (Using Windows binary ver 0.85) I extended Prof. Neumann's code to handle above and it works.(see Code1 below) My experiment(Code 2) works only for the following cases(that I tested): 1. A,B and C has a method "m". 2. The instvar delegate removed from B It does not work when I rename the method "m" in class C to "m2". In this case I expect an object of class B to execute "m" but instead I get an object of class A executing "m" instead. I would be grateful for any pointers to resolve this problem. Also I want to try to implement delegation as described by Prof. Lieberman(OOPSLA 1986 paper). Will be grateful for any pointers on this also. ............... Code1: Prof Neumann's code inelegantly extended Class A -parameter delegate A instproc handleDelegation {result} { if {[[self] exists delegate]} { set context [::info level -1] #look for method in delegated object if {[[[self] set delegate] procsearch [lindex $context 0]] != "" } { ::upvar $result y set y [eval [[self] set delegate] $context] return 1 } } return 0 } A instproc m {x} { if {[[self] handleDelegation r]} { return $r } else { puts "[self] [self class] [self proc] $x"; return [next] } } Class B -parameter delegate B instproc handleDelegation {result} { if {[[self] exists delegate]} { set context [::info level -1] #look for method in delegated object if {[[[self] set delegate] procsearch [lindex $context 0]] != "" } { ::upvar $result y set y [eval [[self] set delegate] $context] return 1 } } return 0 } B instproc m {x} { if {[[self] handleDelegation r]} { return $r } else { puts "[self] [self class] [self proc] $x"; return [next] } } Class D D instproc m2 {x} { puts "[self] [self class] [self proc] $x" next return [expr {$x*2 + [[self] set v]}] } D d1 d1 set v 100 B b1 -delegate d1 A a1 -delegate b1 puts "result = [a1 m 123]" ............................................... Code2: My Try using filters #create SimpleDelegation as a meta-class Class SimpleDelegation -superclass Class SimpleDelegation instproc sdFilter args { set method [self calledproc] if {[[self] exists delegate]} { set del [[self] set delegate] #if delegate has method then dispatch it. if {[$del procsearch $method] != ""} { return [eval [$del $method $args]] } return [next]; } } SimpleDelegation instproc init args { [self] filterappend [self class]::sdFilter next [self] instproc setDelegate {d} { [self] set delegate $d } } SimpleDelegation A -parameter delegate SimpleDelegation B -parameter delegate A instproc m {x} { puts "[self] [self class] [self proc] $x" return [next] } B instproc m {x} { puts "[self] [self class] [self proc] $x" next return [expr {$x*2 + [[self] set v]}] } Class C #method "m" renamed to "m2" here. C instproc m2 {x} { puts "[self] [self class] [self proc] $x" next return [expr {$x*3 + [[self] set v]}] } A a B b a setDelegate b b set v 100 C c b setDelegate c c set v 100 puts "result = [a m 123]" .................................................. Regards, Sheik Yussuff email: sheik(a)carib-link.net

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Tcl stubs
by BRIAN THEADO 11 Jul '01

11 Jul '01

Gustaf Neumann <neumann(a)wu-wien.ac.at> wrote: >the only difficulties i see is >for older tcl-version not supporting the stub library. I encountered some issues with undefined references while trying to build libxotcl.so using stubs on Linux. Here's what I did: Added the following lines to the top of function Xotcl_Init in the file xotcl.c: #ifdef USE_TCL_STUBS if (Tcl_InitStubs(in, "8.1", 0) == NULL) { return TCL_ERROR; } #endif Compiled with the additional flag -DUSE_TCL_STUBS Linked libxotcl.so against libtclstub.a Here are the undefined references I encountered: One set of undefined references was due using the macro version of TclNewObj instead of the function version (Tcl_NewObj) in xotclInt.h. This can be fixed with an extra #ifdef USE_TCL_STUBS The other undefined references stem from the use of the following functions: Tcl_FormatObjCmd Tcl_IncrObjCmd Tcl_InfoObjCmd Tcl_RenameObjCmd Tcl_UplevelObjCmd Tcl_UpvarObjCmd Tcl_VariableObjCmd I'm assuming these can be fixed by using Tcl_EvalObjv to access the Tcl commands instead of calling them directly. I haven't tried it yet, but it seems reasonable to me. ____________________________________________________________________ Get free email and a permanent address at http://www.amexmail.com/?A=1

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broken web links, Tcl stubs
by BRIAN THEADO 08 Jul '01

08 Jul '01

Hello, The links to the XOTcl mailing list and mailing list archive seem to be broken on the page http://media.wu-wien.ac.at/doc/index.html. They seem I found the link on the main XOTcl page to be O.K. Also, I was wondering what the chances are that XOTcl be linked against the Tcl stubs library instead of directly against the Tcl library. This gives the freedom of using the same build of the extension with multiple versions of the TCL interpreter. This would be especially nice for the windows distribution. I don't have a build environment set up in Windows and the dll distributed on the XOTcl web page requires exactly Tcl 8.3 and doesn't work for me with 8.4. Thanks, Brian Theado ____________________________________________________________________ Get free email and a permanent address at http://www.amexmail.com/?A=1

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XotclIDE version 0.17
by Artur Trzewik 06 Jul '01

06 Jul '01

Hallo There is new 0.17 version of XotclIDE available http://www.xdobry.de/xotclide Main Changes: 1. search functions (text, senders, implementors) 2. find/replace dialog in editor 3. error stack editor. parse error stack from $errorInfo and display it in browser. 4. simply debugger. You can set a break point (per send halt message "[self] halt") see call stack, level variables, arguments and all you need to understand your program 5. fist step to multi user environment. The version control system write all changes with userid attribute. 6. many small changes and refactoring ("new catagory" function) Complains about not intuitive GUI are also needed. Artur Trzewik

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re: problem when having both a filter and a Tk callback returning a break
by Gustaf Neumann 06 Jul '01

06 Jul '01

Dear Catherine, here comes a quick fix for this. search for FilterDispatch(Tcl_Interp* in, XOTclObject* obj, int objc, Tcl_Obj* CONST objv[]) { in xotcl.c and replace towards the end of this procedure if (result != TCL_OK) result = TCL_ERROR return result; } by if (result >= XOTCL_UNKNOWN) result = TCL_ERROR; return result; } If you have a problem with this, i can place a patched version of 0.85 on our webserver best regards -gustaf

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problem when having both a filter and a Tk callback returning a break
by Catherine Letondal 05 Jul '01

05 Jul '01

Hi, One problem I have when using Tk and Xotcl together (actually the only one for now), is that when I put a filter on a class (e.g for tracing purpose), the methods which are called by a callback (a Tk binding for example) cannot return a -break return code. Here is an example of an error message: invoked "break" outside of a loop while executing "$view validate o o" (command bound to event) This "validate" method is activated whenever the user enter something in a text widget: ::bind $textwidget <KeyPress> { set view [names object %W] $view validate %K %A } And this method does a return like this: return -code break The problem happens only when a filter is put on the class. What can I do to fix this? -- Catherine Letondal -- Pasteur Institute Computing Center

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change of mailing list host name
by Gustaf Neumann 04 Jul '01

04 Jul '01

Dear List members, Last week, the hostname (actually the alias) of the machine running the XOTcl list has changed. please use for the main entry page of the xotcl list http://alice.wu-wien.ac.at/mailman/listinfo/xotcl and to access the archives, please use http://alice.wu-wien.ac.at/pipermail/xotcl/ instead of the URLs with the hostname wi.wu-wien.ac.at Send submissions to xotcl(a)alice.wu-wien.ac.at best regards -gustaf neumann

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A problem, Parameters and Documentation
by Kristoffer Lawson 27 Jun '01

27 Jun '01

I have a problem where I have many classes which would have a lot of very simple methods to set/get certain attributes. The simplest way is to have lots of instprocs, but that's a lot of cut&pasting as each one is almost the same. Now I'm sure you're all thinking "parameters". Well, originally I thought that would work, but it seems I have misunderstood the parameter documentation. You see, simple parameters wont work. I need the automatically created instprocs to do more than return an instvar. I originally thought that extending Class::Parameter might work, but it now seems that this might not be the case. So what I'm looking for is input and ideas from anyone who cares to share them. In addition I have some comments and questions about XOTcl itself. I'll split this discussion up into a few sections. 1. Parameter Documentation. The bit about extending Class::Parameter at http://media.wu-wien.ac.at/doc/tutorial.html#parameter wasn't exactly clear to me. Especially the line: C c1 {{a -default 1 -someInstproc x} ...} I still can't quite work out what that line is actually doing. Is C a class creating an object called c1? Is it a meta-class creating a class object c1? And in both situations wouldn't the argument just be sent as-is, so no parameter handling? I now understand (after playing around in the shell), that when using the "parameter" method I can additionally specify methods to call in the used parameter class. However, this is not immediately clear from the tutorial. In addition it does not mention what arguments are sent to this procedures and which object receives the messages (I worked it out by testing). In addition I would like to know the calling order. If I use a parameter line like {{a -default 1 -someInstproc x}}, is the parameter "a", and the method for it, created after or before the call to someInstproc? It appears to be after. The role of Class::Parameter is not quite obvious either. It is used to set the default, but am I correct in understanding that it does not actually handle the creation of parameters or their methods? Does it do anything else? Another interesting thing I noticed: when -someInstproc is called above [self callingobject] returns an empty string inside the proc. I could've used that to override the normal method created. 2. My problem in more general terms If I look at my situation from a wider perspective the need I have is to have an interface that looks like parameters to the developer using my library, but which are handled differently internally. I want to easily be able to allow a developer to do the following: set textOb [Text new $root -enabled 1 -text "Hello, world\n"] As mentioned, that is easy to do by providing the methods "enabled" and "text", but as each one is exactly the same I would like a mechanism that is like the parameter one, but handled slightly different internally. In the ENIÄK system those would be referred to as attributes, and the methods basically just translate them to ENIÄK commands. 3. Some solutions 1) Cut&paste. Well, it does the trick, but it's a bit bothersome. 2) Code generation from a separate script. Ugly, hacky and experience shows that it's awkward to maintain. 3) For loops. I could create a whole bunch of similar instprocs for each class in a for loop (hooray for script programming). But it might not be quite obvious to anyone reading the code, plus do I lose the possibility of using xoDoc documentation? 4) Metaclasses. I could create an EniakClass metaclass, which provides each class with a method to create instprocs easily. It would look like the parameter mechanism except that instead of specifying -parameter when creating a class, I could use -attribute. I do not wish to override the parameter method as I use normal parameters as well. That of course means changing a lot of classes from being instances of Class to instances of EniakClass. Still, all in all not a truely horrible solution. 5) Something else? 4. XoDoc With solution 4) above I have the issue of using xodoc and that "-attribute" method invocation when creating a class. Xodoc obviously does not understand that. So I would still like to see a documented way of extending xodoc -generation dynamically on an application level so that certain metatags in certain contexts would generate certain output for different target platforms (ie. something for Html, something for XML etc.). Probably something to keep in mind with future releases. 5. Spoiling all the fun Some of my attributes will most likely have to be handled specially anyway. For those I will just have to make their own procedures. Mostly these specially handled ones are the kind where I don't necessarily want the developer to specify attribute values directly (as some of the protocol attribute values can be cryptic, so I want to map them to clearer forms). The downside to this model is that while they appear the same to the developer they will be implemented (and probably documented) differently than the ones created in the generic way. So am I stuck? - ---------- = = ---------//--+ | / Kristoffer Lawson | www.fishpool.fi|.com +-> | setok(a)fishpool.com | - - --+------ |-- Fishpool Creations Ltd - / | +-------- = - - - = --------- /~setok/

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