A Lisp programmer knows the value of everything, but the cost of nothing.
—Alan J. Perlis
Lisp is not inherently less efficient than other high-level languages.
—Richard J. Fateman
One of the reasons Lisp has enjoyed a long history is because it is an ideal language for what is now called rapid-prototyping–developing a program quickly, with little regards for details. That is what we have done so far in this book: concentrated on getting a working algorithm. Unfortunately, when a prototype is to be turned into a production-quality program, details can no longer be ignored. Most “real” AI programs deal with large amounts of data, and with large search spaces. Thus, efficiency considerations become very important.