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Introduction to Muddle

Background

Muddle, later renamed MDL, was a programming language created by the Dynamic Modeling group (also known as the Programming Technology Division) at MIT. The most famous application written in this language is the Zork interactive fiction game. The influental CLU programming language was bootstrapped from Muddle.

Muddle is a dialect of Lisp, but with the distinct difference that forms are bracketed by < and > instead of parentheses. ( and ) still denote lists and are occasionally present in the language syntax. The language is case sensitive, and all standard names must be entered in upper case. To submit an expression to the interpreter, type the Escape key which echoes as $.

Example

A common way to develop applications in Muddle, is to build a program in the interpreter and write out a SAVE image file. This file can later be recalled using RESTORE.

To make a "hello world" application, create a file called HELLO MUD with this content:

<DEFINE HELLO ()
  <PRINC "Hello, muddled world!">
  <TERPRI>
  <QUIT>>

<DEFINE SAVE-IT ()
  <COND (<=? <SAVE "LARS; HELLO SAVE"> "SAVED"> <QUIT>)>
  <HELLO>>

<SAVE-IT>

HELLO is the main program which prints a message and terminates. SAVE-IT is used to create a SAVE file and arranges to call HELLO when it's restored.

Now start :muddle and type <FLOAD "HELLO MUD"> and Escape. It should look like this:

:muddle
MUDDLE 56 IN OPERATION.
LISTENING-AT-LEVEL 1 PROCESS 1
<FLOAD "HELLO MUD">$

:KILL

A HELLO SAVE file has been created with the HELLO procedure in it. To run it, start :muddle again and type <RESTORE "HELLO SAVE">:

*:muddle
MUDDLE 56 IN OPERATION.
LISTENING-AT-LEVEL 1 PROCESS 1
<RESTORE "HELLO SAVE">$
Hello, muddled world!

:KILL

The sample program can be found in the HELLO directory.

More Information

For more information, see these documents: