Alan Kay said
OOP to me means only messaging, local retention and protection and
hiding of state-process, and extreme late-binding of all things.
What is local retention? Can someone explain with an example from any programming language (e.g. Java,Scala, Lisp, Haskell)
To parse the sentence correctly, "OOP to me means only
messaging
(local retention, protection, and hiding) of state-process
extreme late-binding of all things
"
So I think "local retention ... of state-process" just means that state is kept locally within objects.
Related
Let's say i code a program under an Open Source license like the GPL which uses strong cryptography in a country which has no restrictions about doing so, and no restrictions in making the software publicly available, like hosting on a hosting provider like github for example.
As of this post github stores all or part of the data it is hosting in several datacenters located on the northern american continent. I have read software incorporating strong cryptography falls under a special USA law about ammunition and as i know even written stuff about implementation of strong cryptography is prohibited to export.
So when pushing my local git repo to an account on github.com, does legal issues arise ? If so, what are good alternatives ?
No, the ammo law no longer applies. There is no restriction.
See, Bernstein v. United States. A a set of court cases brought by Daniel J. Bernstein challenging restrictions on the export of cryptography from the United States.
Also DJB created the delightful curve25519 and it's twisted Edwards variant Ed25519.
I'm trying to understand difference between objects/messages in Smalltalk and processes/messages in Erlang. I read the following post on the topic.
As far as I understand, in Smalltalk, everything is an object, and everything has the same "object/message" abstraction - even the number 1 is an object that can only be reached with message passing.
Is 1 a process in Erlang/Elixir? Is everything in Erlang a response to message/program paradigm? Can you send a message to a number in Erlang?
Thanks a lot.
Processes in Erlang and Objects in Smalltalk are indeed the same thing.
At first glance, this is not terribly surprising: Erlang is an Actor Model language. The Actor Model was invented by Carl Hewitt, who based the message-driven evaluation model on Smalltalk's message-driven evaluation model. (Really, Actors and Objects are the same thing; they only differ in some details.) Alan Kay, in turn, was influenced by Carl Hewitt's PLANNER, when he designed Smalltalk.
So, there is a close relationship between Actors and Objects, and therefore, it should not be surprising that Erlang's Processes and Smalltalk's Objects are so similar.
Except for one thing: the designers of Erlang didn't know about the Actor Model!!! They only learned about it later, particularly when Joe Armstrong wrote his PhD Thesis under Seif Haridi (co-author of the definitive book on Programming Paradigms) in the late 1990s.
Joe Armstrong wrote an article in which he strongly advocated against OO (Why OO Sucks), but he later changed his mind when he realized that Erlang is actually very object-oriented. In fact, he even went so far as to claim that Erlang is the only object-oriented language in this interview with Joe Armstrong and Ralph Johnson.
This is an interesting case of what evolutionary biologists would call convergent evolution, i.e. two unrelated species evolving to be similar in response to similar external pressures.
There are still a lot of relationships between Erlang and Smalltalk, though:
Erlang started out as a concurrency extension to Prolog (and even when Erlang became its own separate language, the first implementations were written in Prolog) and is still to this day heavily rooted in Prolog. Prolog is heavily influenced by Carl Hewitt's PLANNER.
Smalltalk was also heavily influenced by what would later become the ARPANet (and even later the Internet); Erlang was designed for networked systems.
However, one of the important differences between Erlang and Smalltalk is that not everything is a Process. 1 is a number, not a process. You can't send a message to a number.
There are multiple "layers" of Erlang:
Functional Erlang: a mostly typical, dynamically-typed functional language with some "oddities" inherited from Prolog, e.g. unification.
Concurrent Erlang: Functional Erlang + Processes and Messages.
Distributed Erlang: Concurrent Erlang + Remote Processes.
Fault-Tolerant Erlang: Distributed Erlang + certain Design Patterns codified in the OTP libraries, e.g. supervisor trees and gen_server.
A Fault-Tolerant system written in Erlang/OTP will typically look like something we might recognize as "Object-Oriented". But the insides of those objects will often be implemented in a more functional than object-oriented style.
Interestingly, the "evolutionary pressure" that Erlang was under, in other words, the problem Erlang's designers were trying to solve (reliability, replication, redundancy, …) is the same pressure that led to the evolution of cells. Alan Kay minored in microbiology, and explicitly modeled OO on biological cells. This is another parallel between Erlang and Smalltalk.
I wrote a little bit about this in another answer of mine.
What is the formal and complete definition of the words "meta-logic" and "object-logic" in Isabelle? I see people keep using these but could not find any definition for these.
You don't find them because they are specific to Isabelle (as far as I know). "Object-logic" and "meta-logic" are terms introduced by Larry Paulson (as far as I can tell). In general, though not specifically, they are related to the general terms "metalanguage" and "object language", for disciplines like logic and set theory. Do a search on those and you'll get the standard wiki pages, because they're a standard part of logic.
Here, I'm looking at page 16, 2.2.3 Meta and object language of Logic and Computation - Interactive Proof with Cambridge LCF, by Larry Paulson, published 1987. At that time he was still conforming to standard terms, but then he switched. I forgot where I read it, but he made the switch somewhere to "meta-logic" and "object-logic", to clarify things for his own purpose. The two terms are in his papers and in the Isabelle distribution docs.
Others can give you their expert knowledge, but the meta-logic specifically is what you get when you import the theory Pure, in particular, a minimal set of logical connectives, ==>, \<And>, &&&, and ==. Discussion of these are spread throughout the Isabelle distribution documentation.
I know nothing much about intuitionistic logic, other than it doesn't provide the law of excluded middle, but you will read that they provide a minimal, intuitionistic logic.
Don't thank me. I've just read some things here and there, and listened. Others can provide expert knowledge.
My findings with regard this question are below.
I found in the Clemens Ballarin slides, slide 20.:
Meta logic: The logic used to formalize another logic.
Example: Mathematics used to formalize derivations in formal logic.
and it is put in parallel with:
Meta language: The language used to talk about another language.
Examples: German in a Spanish class, English in an English class.
Wikipedia has an entry on Metalogic, one section is Metalanguage - Object language:
In metalogic, formal languages are sometimes called object languages.
The language used to make statements about an object language is
called a metalanguage. This distinction is a key difference between
logic and metalogic. While logic deals with proofs in a formal system,
expressed in some formal language, metalogic deals with proofs about a
formal system which are expressed in a metalanguage about some object
language.
And here is slide 21 from Ballarin:
I want to know in which applications/programming domain are most suitable for Smalltalk. Could anyone please provide me some useful links that could answer my query?
Through googling I learned that some companies use it for:
logistics and foreign trade application
desktop, server and script development
data processing and logistics, scripts and presentations
but I cant find documents/research papers that can tell me which programming domain Smalltalk-80 (or Smalltalk) is best suited.
Some of the programming domains are:
- Artificial intelligence reasoning
- General purpose applications
- Financial time series analysis
- Natural language processing
- Relational database querying
- Application scripting
- Internet
- Symbolic mathematics
- Numerical mathematics
- Statistical applications
- Text processing
- Matrix algorithms
I hope you guys can help me. I am doing this for my case study. Thanks in advance.
It's a general purpose programming language. To paraphrase Kent Pitman on the question of what Common Lisp is useful for:
...Please don't assume [Smalltalk] is only
useful for Animation and Graphics, AI,
Bioinformatics, B2B and E-Commerce,
Data Mining, EDA/Semiconductor
applications, Expert Systems, Finance,
Intelligent Agents, Knowledge
Management, Mechanical CAD, Modeling
and Simulation, Natural Language,
Optimization, Research, Risk Analysis,
Scheduling, Telecom, and Web Authoring
just because these are the only things
they happened to list.
It's particularly suited for applications that cannot have downtime - it's quite normal to patch a running server in deep ways (say, by changing the shape of your class) without taking the server down - or systems that are very complex or have rapidly changing requirements.
Smalltalk has quite substantial growth recently in web based applications, thanks to innovations and fresh approaches in Aida/Web, Iliad and Seaside Smalltalk web frameworks.
In general Smalltalk is used for most complex information systems, let me mention just two:
Finance: Kapital, a risk management in JP Morgan
Manufacturing: ControlWorks, for chip manufacturing in AMD
My goal has been to do a brain dump into software. And I have found Smalltalk to be very well suited for that. Smalltalk makes it easy to put my ideas down in code. And it provides feedback to my thinking. The ability to debug infinitely deep at any point in the execution just enhances my understand of the problem to be solved. Then it allows me to carry out my solution most naturally.
Aik-Siong Koh
I'm afraid you will get as many answers as users of Smalltalk. For some it's a "way of life" for others it's a learning process and in the end they "strand" at granddaddy of the OO languages. Some are using their smalltalk as a kind of shell to "IT-problems".
For me the answer is for application development. Now this is definitive a wide field. As you figured out it is used quite "much" in the software for economic stuff. And that is where I'm using it. I've decided to use it for my Web-Development projects which are related to "business".
The domains you named are all suitable for Smalltalk. Smalltalk shows its strengths in development for systems that are engineering-time limited, instead of hardware-limited.
The Seaside web framework allows us to create complex web applications in a fraction of the time needed in other technologies. The Gemstone object-oriented database allows us to nearly ignore persistence issues.
Smalltalk is generally a very expressive, readable, and understandable language. Whenever a large codebase is to be maintained or code needs to be understandable to non-professionals, Smalltalk shines.
»Smalltalk is a vision of the computer as a medium of self expression. … A humanistic vision of the computer as something everyone could use and benefit from. If you are going to have a medium for self expression, programability is key because unless you can actually make the system behave as you want you are a slave to what’s on the machine. So it’s really vital, and so language comes to the for because it’s through language that you express yourself to the machine.« – Elliot Miranda
You can check this link: http://www.clubsmalltalk.org/web/index.php?option=com_content&view=article&id=183&Itemid=117 this is a compilation of uses of smalltalk in latam.
perhaps another way of answering the question would be by stating what it might not be suitable for. One domain would be where you have "real" real time constraints i.e. you would need to control the garbage collector from kicking off. If I recall IBM's (OTI) Smalltalk embedded had a mechanism for turning off the gc, but IBM dropped that a while ago. The other domain I have not seen much of is cell phone apps. As far as I know none of the viable Smalltalk's can run on Android but that may change. One hears of folks in Squeak/Pharo working on that. I would love to see ST running well on Android. I think that the Android tablet market will be a hot one.
I should conclude by saying that in all the years I have been coding in ST i.e. since 94, I have seen Smalltalk in just about everything else.
I cant find documents/research papers that can tell me which programming domain Smalltalk-80 (or Smalltalk) is best suited.
This is because Smalltalk is not a domain-specific language, but a general purpose language.
Things it has been used for in the past:
- as the operating system system language for personal computers
- writing rich multimedia and near real-time applications, such as sound synthesisers
- very large corporate and government data processing systems, such as the UK's Home Office Large Matter Enquiry System, or many of JPMorgan Chase's financial trading systems
- web applications, such as DabbleDB
- creating complicated development tools, such as IBM's VisualAge IDE
- experimenting and prototyping applications in early-stage development
Generally speaking Smalltalk shines where the systems are complex, development speed is a key factor, and maintainability is going to be a key factor.
I use Smalltalk to create applications to control, manage and distribute multi-platform JavaScript webapps.
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I want to ask you to provide me with some articles (maybe books), which you possibly have found very convincing criticising the OOP methodology.
I have read some in the WWW on this topic and I didn't really find a 'definitive demotivator'.
It's not much about my personal attitude to the OOP, but I really would like to have something constructive, rigorous foundation for any kind of discussion and just abstract thinking.
You can post some original research too, but please be very constructive (as my personal request).
Which version of OOP? Alan Kay's original vision? The bastardized modern form of it that misses the point entirely and thus encumbers us with bizarre access control, member variables, etc? Inheritance-centric? Prototype-based? Compositional OOP?
Each form of OOP has its strengths and its weaknesses; its advocates and its detractors; its domains of utility and its domains of uselessness. There's nothing magical about OOP that makes it the Killer Paradigm and there's nothing infernal about it that makes it the Killer (of Programmers) Paradigm.
I can't really point you to any books or articles that killed my interest in OOP as a Silver Bullet (as opposed to one of many techniques I can use to keep my projects survivable). I can point to the funniest critique of a specific brand of OOP, however: Steve Yegge's classic "Execution in the Kingdom of Nouns".
Rick Hickey's Are We There Yet ? - A Deconstruction of Object Oriented Time was an eye opener for me. It's the most logical OO criticism I have come across.
If you want a criticism of OO programming, here's what I'd recommend:
Learn Smalltalk
Learn Erlang
Learn Scheme
Once you've done that, you will have plenty of criticism of the common interpretation of OO programming.
(Hint: OO was in many ways intended to more closely resemble the Actor model of computation, but the common interpretation of it is effectively a modification of the procedural/structured model)
Problem is - most people don't really know Object-Oriented Programming, so many designs SUCK.
Read the works of Scott Ambler, including his (now pretty old) Building Object Applications That Work. This has been eye-opening for quite a lot of people.
Maybe not quite what you were looking for but have a look at the Jan/Feb issue of IEEE Software magazine: Object-Oriented Analysis: Is It Just Theory?. The basic conclusion is that OOA does not provide a good cost/benefit ratio so is poorly utilized.
Given that OOA is not effectively utililzed or supported in the "real world", I suspect that for larger development projects the overall system architecture, deployed object model and class hiearchy end up being sub-optimal and poorly understood (implemented) by various parts of the development team. A second article in the same journal: Four Trends Leading to Java Runtime Bloat point to some common OOP issues that detract from deploying high-volume Java (OOP) systems. The observations made in this article probably apply to most highly architected OOP applications.
Do not take this as OO bashing, it just reflects that as software practictioners we have quite a bit of work to do toward developing better person-to-person communication mechanisms to convey highly complex and abstracted process models.
When you define a process in natural language. You use sentences where you define the subject who will do an action on one or more objects.
The only fix point is the action, the predicate of the sentence.
I don't think assigning actions to objects is a good idea.
There is only one verb, but can be multiple nouns.
In OOP you can write a file in at least 3 ways:
file.write(data);
or
data.writeToFile(file);
or
OperatingSystem.write(file, data);
Which object should implement the method? You need to think about this too.
While in the procedural way, you probably write
write(file, data);
And the only thing you need to think is the order of the operands which is usally does not matter.
(Well file and data may not be the best example but you probably see the point)
You should really see Mr. B. Jacobs's:
OOP Myths Debunked
(also known as OOP Oversold.)
http://cat-v.org has a great page on Object Oriented Programming.
Most of the page consists of humorous but not terribly informative quotes. However, at the bottom of the page are a number of links to articles challenging OOP. They are:
Bad Engineering Properties of Object-Oriented Languages by Luca Cardelli.
Why OO Sucks by Joe Armstrong
Pitfalls of Object Oriented Programming – By Tony Albrecht of Sony Computer Entertainment Europe, Research & Development Division.
Object-Oriented Considered Harmful by Frans Faase.
Object Oriented Programming Oversold!
I Hate Patterns – By Parand Tony Darugar.
Why arc Isn’t Particularly Object-Oriented – By Paul Graham.
The questions about inheritance in the Java IAQ.
Stop Writing Classes – Great talk about how classes are often used and abused. By Jack Diederich.
If you are interested in alternatives to Object-Oriented Programming:
cat-v.org. From their 'about' page: Cat-v.org hosts a series of sites dedicated to diverse subjects that share an idiosyncratic intellectual perspective, questioning orthodoxy and fomenting elitism and high standards in topics from software design to politics, passing by art and journalism and anything else interesting.
Structure and Interpretation of Computer Programs. Specifically teaches functional programming. Available free online here, for sale here. I cannot recommend this highly enough. It is absolutely revolutionary. It will change the way you think.
Any and all writings/videos/lectures by Rob Pike and Steve Yegge. Of particular interest is Yegge's Whirlwind Languages Tour.
I'd recommend learning a different programming paradigm or reading pro arguments for specific paradigms (http://www.info.ucl.ac.be/~pvr/VanRoyChapter.pdf). Besides OOP, I think the most widely used is the functional paradigm (search f.e. "Why functional programming matters"), but also have a look at the other ones. When you start looking at programming from a different perspective, the flaws of OOP start to appear automatically.
Simple exercise: define the objects IPerson, CMale and CFemale and implement the methods "sex" and "reproduce".
hows about steve yegge's execution in the kingdom of the noun
for java style OO
The Gideon Bible of object-oriented design patterns, aptly named Design Patterns. One of the best software design books I've ever read.