1. Program Design in Scheme

2. Program Design  The purpose of software is to provide a useful service -- to help someone else do his job better, improve his life.  Good design is more difficult than good programming.  A software engineer with good design skills has more potential than a good programmer. automatic code generation (based on design documents) will gradually reduce programming  How do we learn good design?

3. Learning Program Design  Think and practice.  Learn from others (read, join a project)  Scheme is often used to teach program design because it encourages small, modular programs. How to Design Programs http://www.htdp.org/ Bruegge, Object-Oriented Software Engineering: Using UML, Patterns, and Java Lethbridge, Object-Oriented Software Engineering: Practical Software Development using UML and Java 219341: Software Specification and Design

4. Scheme Example: Movie Theatre  profit: the theatre's profit is revenue minus cost  revenue: ticket sales times ticket price  cost: fixed operating costs plus pay-per-view costs  sales: depend on ticket price (and movie, of course) What is the purpose of this program? What are the inputs we have control over?

5. Scheme Example: Movie Theatre  profit: the theatre's profit is revenue minus cost  revenue: ticket sales times ticket price  cost: fixed operating costs plus pay-per-view costs 50,000 Baht/day + 20 Baht/view  sales: depend on ticket price (and movie, of course) demand * ( 1 - sensitivity*(ticket price - 50) )  Moviedemandsensitivity "block buster" 15000.04 "hit"10000.06 "good"8000.06 "average"6500.08