- Land of Lisp
- Acknowledgments
- Introduction
- I. Lisp is Power
- 1. Getting Started with Lisp
- 2. Creating Your First Lisp Program
- 3. Exploring the Syntax of Lisp Code
- II. Lisp is Symmetry
- 4. Making Decisions with Conditions
- 5. Building a Text Game Engine
- 6. Interacting with the World: Reading and Printing in Lisp
- 6.5. lambda: A Function So Important It Deserves Its Own Chapter
- 7. Going Beyond Basic Lists
- 8. This Ain't Your Daddy's Wumpus
- 9. Advanced Datatypes and Generic Programming
- III. Lisp is Hacking
- 10. Looping with the loop Command
- 11. Printing Text with the format Function
- Anatomy of the format Function
- Control Sequences for Printing Lisp Values
- Control Sequences for Formatting Numbers
- Printing Multiple Lines of Output
- Justifying Output
- Iterating Through Lists Using Control Sequences
- A Crazy Formatting Trick for Creating Pretty Tables of Data
- Attack of the Robots!
- What You've Learned
- 12. Working with Streams
- 13. Let's Create a Web Server!
- 13.5. Functional Programming Is Beautiful
- IV. Lisp is Science
- 14. Ramping Lisp Up a Notch with Functional Programming
- 15. Dice of Doom, a Game Written in the Functional Style
- The Rules of Dice of Doom
- A Sample Game of Dice of Doom
- Implementing Dice of Doom, Version 1
- Defining Some Global Variables
- Representing the Game Board
- Decoupling Dice of Doom's Rules from the Rest of the Game
- Generating a Game Tree
- Calculating Passing Moves
- Calculating Attacking Moves
- Finding the Neighbors
- Attacking
- Reinforcements
- Trying Out Our New game-tree Function
- Playing Dice of Doom Against Another Human
- Creating an Intelligent Computer Opponent
- Making Dice of Doom Faster
- What You've Learned
- 16. The Magic of Lisp Macros
- 17. Domain-Specific Languages
- 18. Lazy Programming
- 19. Creating a Graphical, Web-Based Version of Dice of Doom
- 20. Making Dice of Doom More Fun
- A. Epilogue
- Index
- About the Author
- Updates
In this chapter, we put together a simple engine for a text adventure game. Along the way, you learned the following:
A game world can be represented by a mathematical graph, consisting of nodes for the places the player can visit and edges for the paths between these places.
You can store these nodes in an association list (alist) called
*nodes*. This alist allows you to look up properties of a node/place by using its name. In the case of our game, the property we’re storing is a description of each node/place.You use the assoc function to look up a key (location name in our example) in an alist.
Quasiquoting is a technique that allows you to insert small bits of computer code into larger pieces of data.
Some Lisp functions accept other functions as arguments. These are called higher-order functions. The
mapcarfunction is the most popular higher-order function in Common Lisp.To replace a value from an alist, you
pushnew items onto the list. Only the most recent value will be reported by theassocfunction.
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