Class 34: Simulation

Held Monday, November 4, 2002

Summary

Today we consider how to make DrScheme simulate potentially unpredictable events, like the rolling of dice or the flipping of coins.

Related Files

• Reading on simulation
• Lab on simulation

Notes

• We'll spend a few minutes talking about course options for next semester for those of you interested in continuing on in CS.
  • CSC152: Data Structures and Algorithms in Java (MTWF 11:00-11:50)
  • CSC195: Special Topics: Memory Management, C, and More (MTWF 3:15-4:05)
  • CSC297: Two credit group independent: Web Programming (Tu 8:30-9:50)
  • Math classes!
• Special guest today: Sam's mom.
• No coffee today. Sorry.
• Are there questions on homework 7?
• Warning: Exam 2 is coming soon (Wednesday or Friday). It will emphasize higher-order procedures.
• No reading for tomorrow.

Overview

• The Problem of Simulation
• Scheme's random procedure
• Simulating the roll of dice
• Lab

Simulation

• At times, we write programs to model real-world situations:
  • The effect of pollutants on a lake
  • The waiting time in line at Wal-Mart
  • The playing of a card or dice game
• Each of these situations has some aspect of unpredicatability (even if we ignore the butterfly flappings of chaos theory)
• Can we write such programs in Scheme?

Random

• Scheme provides a simple procedure, random, to provide some fodder for simulations and any other times that you want to play with unpredictable behavior.
• (random n) produces an "unpredictible" number in the range [0 .. n-1].
• That's all you need to know right now.

Dice

• Here's a simple simulation problem: Simulate the roll of a single six-sided die.
  • Yes, die is the singular of dice
• Here's one possibility

  (+ 1 (random 6))
  

• See the reading for an alternative.

Lab

• Do the lab.
• Reflect?