Class 06: Numbers

Back to Symbols and Lists. On to Procedure Definitions.

Held Monday, September 9, 2002

Summary

Today we continue our exploration of numbers in Scheme.

Assignments

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

Numbers

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

History

Thursday, 29 August 2002

Monday, 9 September 2002

• Added explanation of building silly abcde list.

Back to Symbols and Lists. On to Procedure Definitions.

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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The source to the document was last modified on Mon Sep 9 08:43:37 2002.
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Samuel A. Rebelsky, rebelsky@grinnell.edu