MDL programming language
Encyclopedia
MDL is a descendant of the Lisp
Programming language. (It is different from the MicroStation
Development Language.) Its initial purpose was to provide high level language support for the Dynamic Modeling Group at MIT
's Project MAC. It was initially developed in 1971 on the PDP-10
computer under the Incompatible Timesharing System
.
The initial development team consisted of Gerald Sussman and Carl Hewitt
of the Artificial Intelligence Lab, and Chris Reeve, Bruce Daniels, and David Cressey of the Dynamic Modeling Group. Later, Stu Galley
, also of the Dynamic Modeling Group, wrote the MDL documentation.
MDL was initially known as “Muddle”. This style of self-deprecating humor was not widely understood or appreciated outside of Project MAC and a few other early citadels of information technology. So the name was sanitized to MDL.
MDL provides several enhancements to classical Lisp. It supports several built-in data types, including lists, strings and arrays, and also user-defined data types. It offers multithreaded expression evaluation and coroutines. Variables can carry both a local value within a scope, and a global value, for passing data between scopes. Advanced built-in functions supported interactive debugging of MDL programs, incremental development, and reconstruction of source programs from object programs.
Although MDL is obsolete, some of its features have been incorporated in later versions of Lisp. Gerald Sussman went on to develop the Scheme language, in collaboration with Guy Steele, who later wrote the specifications for Common Lisp
and Java
. Carl Hewitt had already published the idea for the PLANNER
language before the MDL project began, but his subsequent thinking on PLANNER reflected lessons learned from building MDL. Planner concepts influenced languages such as Prolog
and Smalltalk
. Smalltalk and Simula
, in turn, influenced his future work on the Actor model
.
But the largest influence that MDL had was on the genre known as interactive fiction
. An interactive fiction game known as Zork
, sometimes called Dungeon, was first written in MDL. Later, Reeve, Daniels, Galley and other members of Dynamic Modeling went on to start Infocom
, a company that produced many early commercial works of interactive fiction.
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Lisp programming language
Lisp is a family of computer programming languages with a long history and a distinctive, fully parenthesized syntax. Originally specified in 1958, Lisp is the second-oldest high-level programming language in widespread use today; only Fortran is older...
Programming language. (It is different from the MicroStation
Microstation
MicroStation is a CAD software product for 2- and 3-dimensional design and drafting, developed and sold by Bentley Systems. The latest versions of the software are released solely for Microsoft Windows operating systems, but historically MicroStation was available for Macintosh platforms and a...
Development Language.) Its initial purpose was to provide high level language support for the Dynamic Modeling Group at MIT
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
's Project MAC. It was initially developed in 1971 on the PDP-10
PDP-10
The PDP-10 was a mainframe computer family manufactured by Digital Equipment Corporation from the late 1960s on; the name stands for "Programmed Data Processor model 10". The first model was delivered in 1966...
computer under the Incompatible Timesharing System
Incompatible Timesharing System
ITS, the Incompatible Timesharing System , was an early, revolutionary, and influential time-sharing operating system from MIT; it was developed principally by the Artificial Intelligence Laboratory at MIT, with some help from Project MAC.In addition to being technically influential ITS, the...
.
The initial development team consisted of Gerald Sussman and Carl Hewitt
Carl Hewitt
Carl Hewitt is Board Chair of the International Society for Inconsistency Robustness. He has been a Visiting Professor at Stanford University and the University of Keio. In 2000, he became emeritus in the EECS department at MIT....
of the Artificial Intelligence Lab, and Chris Reeve, Bruce Daniels, and David Cressey of the Dynamic Modeling Group. Later, Stu Galley
Stu Galley
Stu Galley is an American developer of interactive fiction who was an Implementor at Infocom. He also served as corporate clerk from incorporation in 1979 to merging with Activision in 1986. He wrote three of Infocom's original interactive fiction titles, The Witness , Seastalker and Moonmist...
, also of the Dynamic Modeling Group, wrote the MDL documentation.
MDL was initially known as “Muddle”. This style of self-deprecating humor was not widely understood or appreciated outside of Project MAC and a few other early citadels of information technology. So the name was sanitized to MDL.
MDL provides several enhancements to classical Lisp. It supports several built-in data types, including lists, strings and arrays, and also user-defined data types. It offers multithreaded expression evaluation and coroutines. Variables can carry both a local value within a scope, and a global value, for passing data between scopes. Advanced built-in functions supported interactive debugging of MDL programs, incremental development, and reconstruction of source programs from object programs.
Although MDL is obsolete, some of its features have been incorporated in later versions of Lisp. Gerald Sussman went on to develop the Scheme language, in collaboration with Guy Steele, who later wrote the specifications for Common Lisp
Common Lisp
Common Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, published in ANSI standard document ANSI INCITS 226-1994 , . From the ANSI Common Lisp standard the Common Lisp HyperSpec has been derived for use with web browsers...
and Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
. Carl Hewitt had already published the idea for the PLANNER
Planner
Planner may refer to:* A diary for planning* Planner programming language* Planner * Urban planner* Route planner* Meeting and convention planner* Planner , part of GNOME Office...
language before the MDL project began, but his subsequent thinking on PLANNER reflected lessons learned from building MDL. Planner concepts influenced languages such as Prolog
Prolog
Prolog is a general purpose logic programming language associated with artificial intelligence and computational linguistics.Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is declarative: the program logic is expressed in terms of...
and Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
. Smalltalk and Simula
Simula
Simula is a name for two programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard...
, in turn, influenced his future work on the Actor model
Actor model
In computer science, the Actor model is a mathematical model of concurrent computation that treats "actors" as the universal primitives of concurrent digital computation: in response to a message that it receives, an actor can make local decisions, create more actors, send more messages, and...
.
But the largest influence that MDL had was on the genre known as interactive fiction
Interactive fiction
Interactive fiction, often abbreviated IF, describes software simulating environments in which players use text commands to control characters and influence the environment. Works in this form can be understood as literary narratives and as video games. In common usage, the term refers to text...
. An interactive fiction game known as Zork
Zork
Zork was one of the first interactive fiction computer games and an early descendant of Colossal Cave Adventure. The first version of Zork was written in 1977–1979 on a DEC PDP-10 computer by Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling, and implemented in the MDL programming language...
, sometimes called Dungeon, was first written in MDL. Later, Reeve, Daniels, Galley and other members of Dynamic Modeling went on to start Infocom
Infocom
Infocom was a software company, based in Cambridge, Massachusetts, that produced numerous works of interactive fiction. They also produced one notable business application, a relational database called Cornerstone....
, a company that produced many early commercial works of interactive fiction.
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