Class 08: Procedure definitions

Held Wednesday, September 6, 2000

Summary

Today we begin to learn how to define our own procedures.

Notes

• Lab:
  • User-Defined Procedures
• Readings:
  • Defining Procedures (for today)
  • Comments in Scheme (for today)
  • Control structures (for Friday)
  • Conditionals (for Friday)
• I've updated yesterday's outline to better reflect what was actually covered.
  • I just wish that I'd written down the morals.
• I've updated the due date on homework 1
• You can download your own copy of DrScheme (for Windows or Mac) at http://www.cs.rice.edu/CS/PLT/packages/drscheme/

Overview

• About procedures
• Lab

Defining Procedures

• Some problems encountered with ``Is grade in the range 0 through 100, inclusive?''
  • How do we know that grade is defined?
  • What if we want to check more than one grade?
  • What if we want to name the expression?
• The solution: Define your own procedures. E.g., "I want a procedure named valid that takes a value named grade as input and determines whether or not the grade is valid by using the formula ....
• In Scheme, you write that as

  (define valid
    (lambda (grade) 
      ...
    )
  )
  

• In lab today and tomorrow, we'll explore procedures.

Lab

Preparation

Scan through the reading.

Ask us questions.

Work

Do the lab.

Reflection

What did you learn?