Class 06: Numbers

Held Monday, September 9, 2002

Summary

Today we continue our exploration of numbers in Scheme.

Assignments

• Read Procedures

Notes

• I wasn't able to get a coffee pot over the weekend. I'll try tonight or tomorrow.
• Are there any questions on homework 1?
• A few of you were confused about the construction of (a (b c) (d (e)))
  • You should build all lists from back to front. 's a step-by-step construction

    > (define elist (cons 'e null))
    > elist
    (e)
    > (define elistlist (cons elist null))
    > elistlist
    ((e))
    > (define de (cons 'd elistlist))
    > de
    (d (e))
    > (define delist (cons de null))
    > delist
    ((d (e)))
    > (define bc (cons 'b (cons 'c null)))
    > bc
    (b c)
    > (define bcde (cons bc delist))
    > bcde
    ((b c) (d (e)))
    > (define abcde (cons 'a bcde))
    > abcde
    (a (b c) (d (e)))
    

  • Here's it all put together

    (cons 'a
          (cons (cons 'b (cons 'c null))
                (cons (cons 'd (cons (cons 'e null) null))
                      null)))
    

Overview

• Lab on Numbers in Scheme
• Reflection

Numbers

• You've already done some exploration of numbers, so there's not much to say.
• Any questions?
• Do the lab on numbers.
• Reflect.