MDL (Model Development Language, or colloquially also referred to as More Datatypes than Lisp or MIT Design Language) is a programming language, a descendant of the language Lisp. Its initial purpose was to provide high-level programming language support for the Dynamic Modeling Group at Massachusetts Institute of Technology's (MIT) Project MAC. It was developed in 1971 on a PDP-10 running ITS and later ran on TENEX, TOPS-20, BSD,

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 called Muddle. 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.

In 1980 Marc Blank and Joel Berez adapted the MDL language to create a subset called ZIL (Zork Implementation Language) which was used extensively by Infocom to create their award winning games.

Code sample

This is a sample of PDP-10 MDL:

<syntaxhighlight lang="clojure">

<DEFINE EXIT-TO (EXITS RMS)

  1. DECL ((EXITS) EXIT (RMS) <UVECTOR [REST ROOM]>)

<MAPF <>

<FUNCTION (E)

  1. DECL ((E) <OR DIRECTION ROOM CEXIT NEXIT DOOR>)

<COND (<TYPE? .E DIRECTION>)

(<AND <TYPE? .E ROOM> <MEMQ .E .RMS>>

<MAPLEAVE T>)

(<AND <TYPE? .E CEXIT> <MEMQ <2 .E> .RMS>>

<MAPLEAVE T>)

(<AND <TYPE? .E DOOR>

<OR <MEMQ <DROOM1 .E> .RMS>

<MEMQ <DROOM2 .E> .RMS>>>

<MAPLEAVE T>)>>

.EXITS>>

</syntaxhighlight>

See also

  • Zork Implementation Language
  • Zork
  • Scheme (programming language)
  • Planner (programming language)

References

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