Tcl object oriented.Object Oriented Programming in Tcl

 

Tcl object oriented.The Jim Interpreter

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Download the O’Reilly App.Jim Tcl – Object Oriented

 

Aug 05,  · In addition to supporting object-oriented programming. Tcl also provides the foundation for building extended OO systems on top. This chapter provides an introduction to these facilities. This is a draft chapter from the book The Tcl Programming Language, now available in print and electronic form from Amazon, Gumroad and others. Tcl objects are typed. An object’s internal representation is controlled by its type. Several types are predefined in the Tcl core including integer, double, list, and bytecode. Extension writers can extend the set of types by defining their own Tcl_ObjType structs. THE TCL_OBJ STRUCTURE Each Tcl object is represented by a Tcl_Obj structure which is defined as follows. TCL does not offer object oriented primitives, but it is flexible enough to accomodate new primitives. This paper decribes a well known technique, object commands, to add some object primitives to TCL. Once you understand how object commands work, you will be able to figure out the code of most object packages and extensions.

 

Tcl object oriented.Tcl – Wikipedia

Basic Object-Oriented Programming in Tcl Over the years, Tcl has suffered from a surplus of object-oriented programming systems without ever having an object-oriented system integrated into the language. With Tcl, the TclOO package has become part of the core language. TclOO can be used with Tcl as a loadable package. (Simple Tcl Only Object Oriented Programming) Stooop is an extension to the great Tcl language written in Tcl itself. The object oriented features of stooop are modeled after the C++ programming language while following the Tcl language philosophy. Aug 05,  · In addition to supporting object-oriented programming. Tcl also provides the foundation for building extended OO systems on top. This chapter provides an introduction to these facilities. This is a draft chapter from the book The Tcl Programming Language, now available in print and electronic form from Amazon, Gumroad and others.
 
 
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Tcl/Tk, 3rd Edition by Clif Flynt
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Existing extensions
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A program is composed of abstract data types where the behaviour of each type is expressed as a set of routines methods , and an object represents an instance of one of these types and contains the data that represent the state of the object.

Alternatives to this include functional programming , although hybrid models also exist. As of 8. In object-oriented programming, programs are structured in terms of abstract data types.

In class-based object systems, a blueprint for an object, called a class is created and then used to produce instances of that object. Other object systems do not provide the notion of a class, but instead provide mechanisms to copy existing objects, along with hooks that can be used to initialize the copy. The original object is called the prototype -based for the new object. In class-based object systems, a class may inherit its attributes and methods from one or more other classes, forming a class hierarchy.

Over time, it became clear that class hierarchies based on inheritance often constrain the program design in ways that are initially unforeseen. Composition , in which smaller, purpose-built objects are aggregated into a more object, is one strategy that can alleviate some of the problems of inheritance.

Delegation is another strategy that can be employed to extend or wrap objects. There are activities such as object oriented analysis OOA and object oriented design OOD that concern themselves with analyzing a system or a solution to a problem in terms of objects and their behaviors.

In Tcl, objects and classes are usually inplemented as commands, and the state of the object is stored in some namespace associated with the command. As of Tcl version 8. It also uses namespaces , but is an entirely separate mechanism from namespace ensemble.

It is also available as an extension for 8. The list of extensions discussed in this page were created in earlier versions where Tcl lacked a built-in OO facility. The most notable of these, which still have relevance because of widespread use and features, are incr Tcl now built on top of TclOO , Snit because of its excellent support for Tk megawidgets and XOTcl which continues to add leading edge oo capabilities.

The rest IMHO are useful only if you are stuck with older versions of Tcl and only of historical interest otherwise. That’s all that’s required. Everything else including classes is optional, if often useful to have. Note that according to this definition, Tk uses an object system for its widgets. Possibly oo is mainstream nowadays. If a language is purely object-oriented such as Ruby , then it is ok. But oo is not the one true solution.

If a language has a different paradigma such as Tcl and others, then it’s nice to have the opportunity to use oo, but not to forget that there are other mechanisms of information hiding.

I have used both, Itcl and Snit , and both do a good job in their way, but in some cases I prefer more language-generic mechanisms such as procedures originated in namespaces where they have private information as well. The true benefit of Tcl is imho the opportunity to use more than one oo extension in one application. This makes Tcl unique compared with the other scripting languages.

Tcl appears ambivalent, at best, about object orientation. Darren New has suggested that “the need for OO techniques is greatly reduced by a language with eval and info and dynamically-sized structures built in. RS : In a smokebreak, I whipped up this hierarchy of things, by weight:. Every “heavier” thing can contain zero or more of “lighter” things. And on each level one can implement “objects”. Most use 4. Databases are fat objects at level 1. As RS aptly observes in ” interp alias “, object methods can be described as syntactic sugar for a certain form of dispatching.

RS interrupts: I’d even go further and say that quite a bunch of what is called OO can be done in pure Tcl without a “framework”, only that the code might look clumsy and distracting. Just choose how to implement instance variables:. The task of frameworks, be they written in Tcl or C, is just to hide away gorey details of the implementation – in other words, sugar it : As an example, here’s a Stack class with push and pop methods:.

A framework would just have to make sure that the above code is functionally equivalent to, e. But bare-bones has its advantages too: in order to see how a clockwork works, you’d better have all parts visible :. In , Liskov and Zilles used the term operation cluster to describe the implementation of an abstract data type , and the term functional abstraction denoted operations that weren’t specific to the definition of some abstract data type.

Class-based systems are suitable for static languages where an object can not exist prior to runtime and therefore relationships between objects must be specified such that they can be processed by a compiler.

In Dynamic languages where objects can be manipulated at runtime it is possible to use the more general and powerful prototype object systems. Class-based systems continue to be used in dynamic languages primarily due to inertia. PYK In the natural world, type is a strictly abstract thing that arises from the study of kinds of things which actually exist in the physical world.

In class-based object-oriented programming, this is inverted such that kind instance is always derived from type class. This break with reality leads to many of the difficulties that arise in object-oriented programming, particulalry in regards on inheritance. The strict hierarchy of types is an unnatural constraint that often gets in the way of modelling systems as they are.

Since the comprehensive list below has grown very long, here is a short list in no particular order of some OO frameworks that are in very widespread use.

Some of these frameworks are intended for general-purpose deployment; others were developed to satisfy the requirements of a specific project. Some of these frameworks are no longer maintained. Category Object Orientation lists several other projects that use a minimum of code to provide a subset of object-oriented facilities. See Programming with Prototypes. The following systems are novel, and marked by the lack of a mechanism to create objects that are based on other objects or classes.

Description In object-oriented programming, programs are structured in terms of abstract data types. Principles An object should not change any shared state. An object should be fully configured prior to first use. An object should not be reconfigured after first use.

Quotes The big idea is “messaging” If you focus on just messaging – and realize that a good metasystem can late bind the various 2nd level architectures used in objects – then much of the language-, UI-, and OS based discussions on this thread are really quite moot. But one shouldn’t start drinking at breakfast. In other words, how you support good programming techniques and good design techniques matters more than labels and buzz words.

The fundamental idea is simply to improve design and programming through abstraction. You want to hide details, you want to exploit any commonality in a system, and you want to make this affordable.

I would like to encourage you not to make object-oriented a meaningless term. I have argued that there are — and must be — useful techniques beyond object-oriented programming and design. RS : In a smokebreak, I whipped up this hierarchy of things, by weight: 1. Just choose how to implement instance variables: in global variables or namespaces or in closures, e.

Category Object Orientation. Arts and Crafts of Tcl-Tk Programming.