View source for Obliq

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{{Infobox programming language
|name = Obliq
|logo = <!-- Filename only -->
|logo caption = 
|screenshot = <!-- Filename only -->
|screenshot caption = 
|paradigms = [[Multi-paradigm programming language|Multi-paradigm]]: [[Imperative programming|imperative]], [[Structured programming|structured]], [[Modular programming|modular]], [[Object-oriented programming|object-oriented]], [[Prototype-based programming|prototype-based]], [[Parallel computing|parallel]]
|family = [[Niklaus Wirth|Wirth]] [[Oberon (programming language)|Oberon]]
|designers = Krishna Bharat<br />Marc H. Brown<br />[[Luca Cardelli]]
|developer = <!-- or: |developers = -->
|released = {{Start date and age|1993}}
|latest release version = 
|latest release date = <!-- {{Start date and age|1995|mm|dd|df=yes}} -->
|latest preview version = 
|latest preview date = <!-- {{Start date and age|1995|mm|dd|df=yes}} -->
|typing = [[Strong and weak typing|Strong]], [[Dynamic typing|dynamic]]
|scope = [[Lexical scope|Lexical]] pure
|programming language = [[Modula-3]]
|discontinued =
|platform = [[IA-32]]
|operating system = 
|license = 
|file ext = 
|file format = <!-- or: |file formats = -->
|website = {{URL|www.cc.gatech.edu/gvu/people/Phd/Krishna/VO/VOHome.html}}
|implementations = Obliq, Visual Obliq
|dialects = 
|influenced by = [[Modula-3]], [[Self (programming language)|Self]], [[Oberon (programming language)|Oberon]]
|influenced = 
}}

'''Obliq''' is an [[Interpreted language|interpreted]], [[Object-oriented programming|object-oriented]] [[programming language]] designed to make [[Distributed computing|distributed]], and locally [[Thread (computing)|multithreaded]], computing simpler and easier to program, while providing program safety and an [[Implicit type conversion|implicit type]] system. The interpreter is written in [[Modula-3]], and provides Obliq with full access to Modula-3's [[Computer network|network]] [[Object (computer science)|objects]] abilities. A [[type inference]] algorithm for record concatenation, subtyping, and recursive types has been developed for Obliq. Further, it has been proved to be [[NP-completeness|NP-complete]]<ref>{{Cite web | url=http://www.cs.ucla.edu/~palsberg/paper/ic04.pdf | title=Type Inference for Record Concatenation and Subtyping | access-date=2024-05-19 | date=2003-09-22 | first1=Jens | last1=Palsberg | first2=Tian | last2=Zhao}}</ref>
and its lowest complexity to be {{math|''Ο''(''n''<sup>3</sup>)}} or if under other modeling up to certain conditions down to {{math|''Ο''(''n''<sup>2</sup>)}}<ref>{{Cite journal
 |volume=5
 |issue=1
 |pages=57–72
 |last=Henglein
 |first=Fritz
 |title=Breaking through the ''n''<SUP>3</SUP> barrier: Faster object type inference
 |journal=Theory and Practice of Object Systems
 |year=1999
 |doi=10.1002/(SICI)1096-9942(199901/03)5:1<57::AID-TAPO5>3.0.CO;2-U
}}</ref>  and its best known implementation runs in {{math|''Ο''(''n''<sup>5</sup>)}}.<ref>{{Cite conference
 |publisher=IEEE Computer Society
 |doi=10.1109/LICS.2002.1029822
 |page=125
 |last1=Palsberg
 |first1=Jens
 |last2=Zhao
 |first2=Tian
 |title=Efficient Type Inference for Record Concatenation and Subtyping
 |book-title=Logic in Computer Science, Symposium on
 |location=Los Alamitos, California, USA
 |year=2002
|isbn=0-7695-1483-9
 }}</ref>{{Contradictory inline|date=March 2021}}
Obliq's syntax is very similar to Modula-3, the biggest difference being that Obliq has no need of explicit typed [[Variable (computer science)|variables]] (i.e., a variable can hold any [[data type]] allowed by the type checker and if does not accepts one, i.e., a given expression execution error will display) although explicit type declarations are allowed and ignored by the interpreter. The basic data types in the language include [[Boolean data type|booleans]], [[Integer (computer science)|integers]], [[Floating-point arithmetic|reals]], [[Character (computing)|characters]], [[String (computer science)|strings]], and [[Array data structure|arrays]]. Obliq supports the usual set of sequential [[Control flow|control structures]] (conditional, iteration, and exception handling forms), and special control forms for concurrency (mutexes and guarded statements). Further, Obliq's objects can be cloned and safely copied remotely by any machine in a distributed network object and it can be done safely and [[Location transparency|transparently]].<ref>{{Cite book
 |last1=Briais
 |first1=Sebastien
 |last2=Nestmann
 |first2=Uwe
 |year=2002
 |title=FMOODS '02
 |chapter=Mobile Objects "must" Move Safely
 |pages=129–146
 |citeseerx=10.1.1.23.4787
}}</ref>

Obliq's large [[standard library]] provides strong support for mathematical operations, [[input/output]] (I/O), [[Persistence (computer science)|persistence]], thread control, graphics, and animation. Distributed computing is object-based: objects hold a state, which is local to one [[Process (computing)|process]]. Scope of objects and other variables is purely [[Lexical scope|lexical]]. Objects can call methods of other objects, even if those objects are on another machine on the network. Obliq objects are simply collections of named fields (similar to slots in [[Self (programming language)|Self]] and [[Smalltalk]]), and support [[Inheritance (object-oriented programming)|inheritance]] by delegation (like Self).

The common uses of Obliq involve programming over networks, 3D animation,<ref>{{cite journal |last1= Najork |first1=Marc A. |last2=Brown |first2= Marc H. |date= 30 June 1995 |title= Obliq-3D: A High-Level, Fast-Turnaround 3D Animation System |journal= [[IEEE Transactions on Visualization and Computer Graphics]] |volume= 1 |issue= 2 |pages= 175–193 |doi= 10.1109/2945.468402}}</ref> and distributed computing, as occurs over a [[local area network]] (LAN) such as [[Ethernet]]. Obliq is included free with the [[Digital Equipment Corporation]] (DEC) Modula-3 distribution, but other free versions exist elsewhere including [[Compiler|precompiled]] binaries for several [[operating system]]s.

==Projects using Obliq==
*The ''Collaborative Active Textbooks'' (CAT)<ref name=DecSrcRr142>{{Cite web |url=http://gatekeeper.research.compaq.com/pub/DEC/SRC/research-reports/abstracts/src-rr-142.html |archive-url=https://web.archive.org/web/20060411075442/http://gatekeeper.research.compaq.com/pub/DEC/SRC/research-reports/abstracts/src-rr-142.html |url-status=dead |archive-date=2006-04-11 |title=Collaborative Active Textbooks: A Web-Based Algorithm Animation System for an Electronic Classroom; Research Report 142 |last1=Brown |first1=Marc H. |last2=Najork |first2=Marc A. |website=[[DEC Systems Research Center]] (SRC) |publisher=[[Digital Equipment Corporation]] (DEC) |date=May 1996 |access-date=2021-10-08 }}</ref> developed using Obliq applets<ref name=DistributedApplets /><ref name=":oblets">{{cite journal  |last1= Najork |first1=Marc A. |last2=Brown |first2= Marc H. |date= May 1996 |title= Distributed Active Objects |journal= Computer Networks and ISDN Systems |volume= 28 |issue= 7–11 |pages= 1037–1052 |doi= 10.1016/0169-7552(96)00033-5}}</ref> and the Zeus<ref name=DecSrcRr075>[https://web.archive.org/web/20040304053119/http://gatekeeper.research.compaq.com/pub/DEC/SRC/research-reports/abstracts/src-rr-075.html Zeus: A System for Algorithm Animation and Multi-view Editing] Marc H. Brown. [[Digital Equipment Corporation]] (DEC) [[DEC Systems Research Center|Systems Research Center]] (SRC) Research Report 075 (February 1992)</ref> algorithm animation System (written in [[Modula-3]]).
*Obliq applets (Oblets)<ref name=DistributedApplets>{{Cite conference  |publisher=ACM |doi=10.1145/1120212.1120344 |isbn=0-89791-926-2 |pages=204–205 |last1=Brown |first1=Marc H. |last2=Najork |first2=Marc A. |title=Distributed applets |book-title=CHI '97 extended abstracts on Human factors in computing systems: looking to the future |location=Atlanta, Georgia |access-date=2010-05-15 |year=1997 |url=http://portal.acm.org/citation.cfm?id=1120344&dl=GUIDE&coll=GUIDE&CFID=90381905&CFTOKEN=58876735|url-access=subscription}}</ref><ref name=":oblets"/> special web browser (written in [[Modula-3]]) Obliq web page embedded applications.<ref>{{Cite AV media | url=http://www.ibiblio.org/openvideo/video/chi/chi97_02_m1.mpg | format=MPG | title=Distributed Applets | website=www.ibiblio.org | access-date=2024-05-19}}</ref>

==References==
{{Reflist}}

==External links==
*{{Official website|www.cc.gatech.edu/gvu/people/Phd/Krishna/VO/VOHome.html}}
*[[Luca Cardelli]]'s [https://web.archive.org/web/20081017195547/http://lucacardelli.name/Obliq/Obliq.html Obliq Quick Start] page (archived on 2008-10-17)

{{Modula, Oberon}}

[[Category:Modula programming language family]]
[[Category:Oberon programming language family]]
[[Category:Prototype-based programming languages]]
[[Category:Procedural programming languages]]
[[Category:Systems programming languages]]
[[Category:Programming languages created in 1993]]
[[Category:Dynamically typed programming languages]]