MDL (programming language): Difference between revisions

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'''MDL''' (the MIT Design Language) is a descendant of the [[Lisp programming languageLisp_programming_language|Lisp]] [[programmingProgramming]] language. It allows user-defined data types and had some advanced I/O features. Its syntaxinitial distinguishespurpose amongwas executableto lists,provide non-executablehigh lists,level strings,language andsupport arrays,for andthe betweenDynamic globalModeling andGroup localat values[[Massachusetts_Institute_of_Technology|MIT]]'s of variables[[Project_MAC]]. AlthoughIt MDLwas isinitially obsolete,developed somein of1971 itson featuresthe have been[[PDP-10]] incorporatedcomputer inunder laterthe versions[[Incompatible ofTimesharing System]] Lisp.

The inital 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's claim to fame is that it was used to write the original version of the [[Zork]] [[computer game]].

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Although MDL is obsolete, some of its features have been incorporated in later versions of Lisp.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.

MDL was originally named "Muddle", and was designed for the Dynamic Modeling Group at [[Massachusetts Institute of Technology|MIT]]'s [[Project MAC|Laboratory for Computer Science]] and implemented on the [[PDP-10]] computer under the [[Incompatible Timesharing System]].

[[Category:Dynamically-typed programming languages]]