MOO (programming language)

Infobox programming language
name = MOO

paradigm = multi-paradigm: structured, Prototype-based
year = 1990
designer = Stephen F. White
developer = Stephen F. White & Pavel Curtis
latest release version = 1.7.6
latest release date = August, 1993
typing = dynamic
implementations = MOO
dialects =
influenced_by = Algol, Lisp, Scheme, Smalltalk, Self, C
influenced = CoolMUD, ColdC

The MOO programming language is a programming language used to support the MOO system. It is a dynamically typed prototype based object oriented system, with syntax roughly derived from the Algol school of programming languages.

The language has explicit exception handling control flow, as well as traditional looping constructs. A verb and property hierarchy provides default values to prototype objects, with over-riding values lower in the hierarchy. This hierarchy of objects is maintained through delegation to an object's "parent" property, resulting in a form of single inheritance. Special security-related attributes of objects, verbs, and properties include ownership, and read, write and execute flags. MOO programs are byte-code compiled, with implicit decompilation when editing, providing a canonical form of programs.

MOO programs are orthogonally persistent through periodic checkpoints. Objects are identified by a unique integer identifier. Unused program data is eliminated through automatic garbage collection (implemented by reference counting). However, MOO objects themselves are not garbage collected and are manually deleted by their owners or superusers (aka wizards) through a process called 'recycling.'

MOO is explicitly a multi-user system and programs (verbs) are contributed by any number of connected users. A distinction is made between the 'driver' (runtime) and 'core' (programs written in the MOO language.) The vast majority of the functionality of a running MOO is handled 'in-core.'

The runtime supports multi-tasking using a retribution based time slicing method. Verbs run with exclusive access to the database, so no explicit locking is necessary to maintain synchronization. Simple TCP/IP messaging (telnet compatible) is used to communicate with client sockets, each of which is identified with a 'player' in the Virtual reality representation system.

The language supports weak references to objects by number, and to properties and verbs through strings. Built-in functions to retrieve lists of properties and verbs exist, giving the language runtime facilities for reflection. The server also contains support for wildcard verb matching, so the same code can easily be used to handle multiple commands with similar names and functions.

Available sequence types in MOO are lists and strings. Both support random access, as well as head and tail operations similar to those available in functional programming languages like Lisp. All operations on lists and strings are non-destructive, and all non-object datatypes are immutable. Built-in functions and libraries allow lists to also be used as associative arrays and ordered and unordered sets.

Example

@program toy:wind if (this.location = player) if (this.wound < this.maximum) this.wound = this.wound + 2; player:tell("You wind up the ", this.name,"."); player.location:announce(player.name, " winds up the ", this.name,"."); if (this.wound >= this.maximum) player:tell("The knob comes to a stop while winding."); endif else player:tell("The ",this.name," is already fully wound."); endif else player:tell("You have to be holding the ", this.name,"."); endif . [ [http://www.fringenet.net/MOO/yduJtut.txt yduJ's Programming Tutorial] ]

See also

* MOO (game system)

Notes and references

External links

* The [http://www.ipomoea.org/moo/pm1.8.1/ LambdaMOO Programmer's Manual] is the definitive reference for the MOO programming language.

* [http://www.amazon.com/Secrets-Mud-Wizards-Programming-Role-Playing/dp/0672307235 Secrets Of The Mud Wizards] Chapter 14: Programming MOOs is a 60 page tutorial.