Monthly Archives: May 2006

Better Abstractions

A common complaint about Object-Oriented Programming (OOP) is that classes can make simple data hard to deal with: “I don’t want a DirectoryList object, I just want a list of strings.” I would say this is not a flaw inherent … Continue reading

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Types Are Not Classes, But Why?

In Common Lisp, you can’t do this: (defgeneric g (x)) (defmethod g ((x (and integer (satisfies evenp))) …) Because (and integer …) is not a class. It is a valid type specifier and thus could be used in declarations, but … Continue reading

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A Textual CAPTCHA in Lisp

Playing with the first in a (hopefully ongoing) series of Common Lisp Quizzes, I wrote a simple text-only CAPTCHA (completely automated public Turing test to tell computers and humans apart). My solution and others are posted at CL Quiz #1. … Continue reading

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