Class 04: Starting Scheme

Held Friday, January 26, 2001

Summary

Today we begin our investigations of the core language for the course, Scheme. Scheme is a simple functional language with many imperative features and very little syntax.

Assignments

• Read Atoms and Lists

Notes

• Are there questions on homework 1?
  • I'm working on some documentation for doing logical-style formatting in HTML. I hope to have it ready on Monday.
• I'll take questions on today's reading after the introductory stuff.

Overview

• Scheme basics
• Labs
  • DrScheme
  • Beginning Scheme
• Reflection

Scheme Basics

• Scheme is generally used in an interactive environment: You type syntactically-valid expressions and Scheme returns their values.
  • Later this semester, we'll see how to use Scheme in different environments.
• Scheme's syntax is fairly simple: Since almost everything in Scheme involves the application of a function to some arguments, you write:
  • an open parenthesis;
  • the name of the procedure;
  • a space;
  • the parameters to the procedure (separated by spaces); and
  • a close parenthesis.
• For example,

  (+ 2 3 4)
  (sqrt 4)
  (expt 2 3)
  

• If you remember this basic syntactic structure, you'll rarely get syntactic errors from Scheme.

Some Procedures You Should Know

• +: Sum its parameters.
• *: Compute the product of its parameters.
• -: Subtract the second parameter from the first.
• (sqrt val): Compute the square root of val.
• (expt v p): Compute v^p.
• (abs v): Compute the absolute value of v.

Labs

• You'll need to figure out DrScheme before you can write any Scheme, so start with The DrScheme Lab.
• After a little while of playing with DrScheme, you should be ready for the Beginning Scheme lab.
• I hope to spend the last few minutes of class giving you a chance to reflect on your first experiences with Scheme.