Flavors (programming language)

Flavors,^[1] an early object-oriented extension to Lisp developed by Howard Cannon at the MIT Artificial Intelligence Laboratory for the Lisp machine and its programming language Lisp Machine Lisp, was the first programming language to include mixins.^[2] Symbolics used it for its Lisp machines, and eventually developed it into New Flavors; both the original and new Flavors were message passing OO models. It was hugely influential in the development of the Common Lisp Object System (CLOS).^[3]

Implementations of Flavors are also available for Common Lisp.^[4]

New Flavors replaced message sending with calling generic functions.

Flavors offers :before and :after daemons with the default method combination (called :daemon).

Flavors and CLOS features comparison

Flavors offers a few features not found in CLOS:

• Wrappers
• Automatic lexical access to slots using variables within methods.
• Internal flavor functions, macros and substs.
• Automatically generated constructors.
• DEFFLAVOR options: :required-methods, :abstract-flavor, :mixture.
• SEND function for sending messages.

CLOS offers the following features not found in Flavors:

• Multimethods
• Methods specialized on individual objects (via EQL).
• Methods specialized on Common Lisp types (symbol, integer, ...).
• Methods specialized on def-struct types.
• Class slots.

Terminology

Flavors terminology

Flavors	CLOS
flavor	class
component flavor	superclass
dependent flavor	subclass
local component flavor	direct superclass
local dependent flavor	direct subclass
generic function	generic function
combined method	effective method
method option	method qualifier
instance	instance
instance variable	slot
ordering of flavor components	class precedence list

References

1. Howard Cannon, Flavors: A non-hierarchical approach to object-oriented programming, Symbolics Inc., 1982
2. pg 46 of Thompson, C. W., Ross, K. M., Tennant, H. R., and Saenz, R. M. 1983. "Building Usable Menu-Based Natural Language Interfaces To Databases". In Proceedings of the 9th international Conference on Very Large Data Bases (October 31 – November 2, 1983). M. Schkolnick and C. Thanos, Eds. Very Large Data Bases. Morgan Kaufmann Publishers, San Francisco, CA, 43–55.
3. "Symbolics (1985) was using New Flavors (a message-sending model, like Java today), Xerox was using CommonLoops, Lisp Machine Incorporated was using Object Lisp (Bobrow, 1986), and Hewlett-Packard proposed using Common Objects (Kempf, 1987). The groups vied with each other in the context of the standardization effort going on for Common Lisp at the time and finally settled on a standard based on CommonLoops and New Flavors." p. 108 of Veitch 1998.
4. Flavors for Allegro CL

• Veitch, Jim (1998). "A History and Description of CLOS". In Salus, Peter H. (ed.). Handbook of Programming Languages, Volume IV: Functional and Logic Programming Languages (1st ed.). Macmillan Technical Publishing. pp. 107–158. ISBN 1-57870-011-6.

Further reading

• Moon, David A. (June 1986). "Object-Oriented Programming with Flavors" (PDF). Conference proceedings on Object-oriented Programming Systems Languages and Applications. OOPSLA '86. pp. 1–8. doi:10.1145/28697.28698. ISBN 978-0-89791-204-4. S2CID 17150741. Retrieved March 17, 2022.
• "Flavors, Technical Report", MIT Artificial Intelligence Laboratory, Cambridge (Mass.), 1980
• Daniel Weinreb and David A. Moon, "Flavors: Message Passing in the Lisp Machine", A.I. Memo No. 602, November 1980, MIT AI Lab