# Class 34: Simulation

Back to Script-Fu Concluded. On to Program Input and Output.

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

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.

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.

## History

Thursday, 29 August 2002 [Samuel A. Rebelsky]

Monday, 4 November 2002 [Samuel A. Rebelsky]

Back to Script-Fu Concluded. On to Program Input and Output.

Disclaimer: I usually create these pages on the fly, which means that I rarely proofread them and they may contain bad grammar and incorrect details. It also means that I tend to update them regularly (see the history for more details). Feel free to contact me with any suggestions for changes.

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Samuel A. Rebelsky, rebelsky@grinnell.edu