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
FlavorsCLOS
flavorclass
component flavorsuperclass
dependent flavorsubclass
local component flavordirect superclass
local dependent flavordirect subclass
generic functiongeneric function
combined methodeffective method
method optionmethod qualifier
instanceinstance
instance variableslot
ordering of flavor componentsclass 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
  • "A History and Description of CLOS", by Jim Veitch. Pages 107–158 of Handbook of Programming Languages, Volume IV: Functional and Logic Programming Languages, ed. Peter H. Salus. 1998 (1st edition), Macmillan Technical Publishing; ISBN 1-57870-011-6

Further reading
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