Announcing XOTcl 1.5.0
*************************

Hi everybody. We are pleased to announce the availability of XOTcl 1.5.0.
Major changes relative to 1.4.0 are:

    * Improved Functionality

       + The C-level implementation of XOTcl creates now the basic
         classes ::xotcl::Object and ::xotcl::Class completely without
         any methods. All predefined methods are now registered from
         the initialization script-code (predefined.xotcl) via the new
         command
 
             ::xotcl::alias <class>|<obj> <methodName> \
                      ?-objscope? ?-per-object? <cmdName>

          which is used for registering predefined Tcl commands as
          methods. These aliases are like zero cost forwarders, since
          they lookup the function pointer from the commands and used
          these in the methods.

          This change makes it possible to register the same command
          on different classes (with maybe different names), such that
          for example the predefined set method of ::xotcl::Object can
          be replaced with a different method and the set method can
          be registered on some other classes (maybe some application
          classes).

          This change makes it as well quite easy to develop some
          other object oriented languages based on the XOTcl
          framework, since all methods can be rearrange from the Tcl
          layer .


       + Slots

          A slot is a meta-object that manages property-changes of
          objects. A property is either an attribute or a role of an
          relation.

          In a nutshell, a slot has among other attributes 
            - a  name (which it used to access it), 
            - a domain (object or class on which it can be used) , and
            - can be multivalued or not

          Every slot defines a uniform interface to access its
          content.  So has for example, every multivalued slot a
          method "add" to add a value to the list of values and a
          method "remove" to remove it again.

          We distinguish between system slots (predefined slots like
          class, superclass, mixin, instmixin, filter, instfilter) and
          application slots (e.g.  attributes of classes).

         System Slots
         ========

         System slots are predefined slots defining e.g. some relations
         between classes, or between objects and classes. 

         The predefined system slots are:
         - superclass: every class in XOTcl has one or more superclasses.
            The name of this slot is "superclass", the domain is "::xotcl::Class",
            the slot is multivalued.  One object might have multiple superclasses.
         - class: every object has a class; therefore, the domain of the slot
            is "::xotcl::Class", the property is not multivalued.
         - mixin: every object in XOTcl can have one or more mixin classes.
            The name of this slot is "mixin", the domain is "::xotcl::Object", the slot is
            multivalued.
         - instmixin: same as above, but the domain is "::xotcl::Class"
         - filter, instfilter: similar to "mixin" and "instmixin"

         Every slot can be used set and query the property from its domain.
         The syntax for setting values is
           <object> <property> newValue
         and for getting its values is
           set x [<object> <property>]

         Every multivalued slot has as well a method "add" and "remove"

         Examples for using the system slot "mixin"

            Object o; Class M; class N
            o mixin ::M        ;# replacing the per-object mixins of o with M
            o mixin add ::N        ;# add N to the front of the mixin list
            o mixin delete ::M   ;# delete M from the mixin list
            puts [o mixin]         ;# query the current mixin list
        
 
         Attribute Slots
         =========

         Attribute slots are used to manage the setting and querying
         of instance variables. We define now a person with three
         attributes,"name", "salary" and "projects".
   
           Class Person -slots {
             Attribute name
             Attribute salary -default 0
             Attribute projects -default {} -multivalued true
           }

         Examples for using the slots are

           Person p1 -name "Joe"        
           p1 projects add project1

         Some additional features of the slots are:

          - Support for value checking for 
               * primitive types (all types from "string is", like integer, 
                  boolean, ...)
               * instances of Classes (e.g. value must be an instance
                  of Person)
               * custom value checkers
               * uniform interface for single and multi-valued slots

            - Support for lazy initialization (e.g. when costly
               commands (like SQL) are used to initialize instance
               variables, not all variables are used for each object)
        
             - more experimental low-level functionality, like
               * initcmd (executed, whenever the variable is read the first time)
               * valuecmd (executed, whenever the variable is read)
               * valuechangedcmd (executed, whenever the variable is altered)
              
           For more details, see http://media.wu-wien.ac.at/doc/tutorial.html#slots


       + Re-implementation of the method "parameter" based on slots.
           All forms except 
               ... -parameter {name1 {name2 default2}} ...
           (I.e. pure accessor parameters and parameters with
           defaults) are deprecated, since slots are the much more
           powerful and orthogonal construct.

           The old c-based parameter support based on "parameterclass"
           is deprecated. It is still in the C-code (the method "parameter"
           is redefined in predefined.xotcl). If someone urgently needs
           it, please remove the parameter instproc from predefined
           for the time being, and write an email to me, in case
           you really need it). The C code for parameter will be removed
           in the next release.

       + Improved introspection though the procsearch method. This
           method reports now in its second argument not only
           [inst]proc but as well [inst]forward, [inst]parametercmd
           and [inst]cmd (the latter for methods implemented in C.

        * Improved introspection through "info"
           - new subcommand "info slots"
           - implemented backwards bug-compatible "info parameter",
              deprecated

       + Improved serializer
           - better handling of cyclical dependencies, when mixins are involved
           - fix for namespace handling to make the XOTcl communication 
              library classes working with the aolserver (thanks for Stefan Sobernig 
              for pointing this out)
           - Now other ::xotcl::* objects can be included in the aolserver blueprint 
              (e.g. non positional argument handlers)
           - handling of slot dependencies
           - more convenient calling of the serializer:
              Method "serialize" for Object is defined when the package xotcl::serializer
              is loaded.

       + Improved forwarding commands
            - New option for the argument substitution. When the argument
               list of the forward command contains "%argclindex {a b c}", then
               depending of the number of arguments at invocation "a", "b"
               or "c" is substituted. If more arguments are used at the invocation
               of the forwarder than values are contained in the list after %argclindex,
               an error is generated.
            - New options for forwarder: 
               * The option -earlybinding can be used to look 
                  up the function  pointer of the called Tcl command at 
                 definition time of the forwarder instead of invocation time. 
                 This option should only be used for calling C-implemented Tcl commands)
               * The option -verbose prints the substituted command in the forwarder
                  prior to invocation.

       + New snit-like utility functions:
            - ::xotcl::myvar varName: return the fully qualified variable name 
               of the specified variable.
            - ::xotcl::myproc methodName ?args?: call an xotcl method without the need 
               of using "[list [self] methodName ...]"
            Both commands are namespace exported

       + added "subst" to the set of Tcl imported methods (like e.g. incr, append, ...)
          On can do now:
            % Object o
            ::o
            % o subst {I am [self]}
            I am ::o

       + added new method for ::xotcl::Object named "contains":
           This method is essentially a value added back-port 
           of the OpenACS version. It allows one to create a nested
           object structure with little syntactic overhead. See tutorial
           or language reference for more details.

     * Improved code quality: 
       + fixed a bug with nonpositional arguments, some 
           positional arguments and "args"
       + fixed a bug in nonpositional arguments when called without 
           arguments
       + tested with Tcl 8.4.13 and 8.5a4
       + improved error messages in connection with nonpositional arguments
       + fixed a bug in the xotcl trace module (many thanks to jima for reporting)
       + fixed a namespace bug in ::xotcl::package require in connection with xotclide 
           (many thanks to Bill Paulsen and Artur Trzewik for identifying the problem and
           suggesting a fix)
       + improved documentation (e.g. new sections added, 
           some sections deleted, spelling improved, in total 8 pages longer)
       + fixed documentation bugs (many thanks for Kristoffer for reporting)
       + more regression tests added

 For more details about the changes, please consult the ChangeLog and
 documentation.

MORE INFO
  General and more detailed information about XOTcl and its components
  can be found at http://www.xotcl.org


Best regards,

Gustaf Neumann
Uwe Zdun


