LISP and the Common Lisp Object System CLOS

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LISP and the Common Lisp Object System (CLOS)

• Ron Ferguson
• College of Computing
• rwf_at_cc.gatech.edu
• http//www.cc.gatech.edu/faculty/Ron.Ferguson

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LISP is really, really old

• 1959
• Lambda calculus
• Syntax? Parentheses
• Manipulation of list structures
• Equivalence of programs and data
• Slow? Interpreted?

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LISP is really, really cutting-edge

• Garbage collection
• Functional programming
• Extremely powerful macro facility - Why
  write a program when you can write a
  whole new language? - Roll-your-own
  control structures
• Compiles down to fast executable - Type
  specifications are optional
• Used for real applications Orbitz and
  YahooStores

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First ANSI OOP Language?

• C? Java?
• LISP
• ANSI Common Lisp Object System
• Previous LISP Flavors, LOOPS
• Fully object-oriented
• Includes meta object layer
• Spec available online
• http//www.lispworks.com/reference/HyperSpec/
• http//www-2.cs.cmu.edu/Groups/AI/html/cltl/cltl2.
  html
• Multiple free implementations
• See http//www.alu.org

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Creating a simple OOP system in LISP

• Miniature version of classes in GeoRep, an
  existing LISP system
• Qualitative spatial reasoning
• Diagrams
• Begin with a few simple class definitions

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Defining classes in LISP

• Lets go right to the system (Franz Allegro
  Common Lisp)

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Lessons

• Create classes using DefClass
• For each slot, tell the system how it should be
  handled
• The system will create a set of constructor and
  accessor functions
• Use generic methods to specialize functionality
  for a class
• Special methods such as printing
• Use for effects like lazy evaluation

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How to learn more

• Guy Steeles Common LISP
• Anything by Paul Graham
• Association of Lisp Users http//www.alu.org.
• LISP Summer Camp
• Keep eye on my web site
• May accept a few undergrads this year