Thu Sep 16

Questions?

old business

Let's discuss some of the homework. (I've posted my solutions.)

new business

I've posted the next homework assignment, starting two new sections of the book (2.1, 1.3) and learning some new syntax .

First, a new (and more general way to create functions: lambda (or λ) .

Second, a way to define local variables : let .

It turns out that you can define let in terms of lambda ... as explained in the text (and the example here) ... and which I've asked you to describe in the homework.

And finally, we want to start looking at data structures , not just numbers and strings.

The (awkwardly named) functions in scheme are : car, cons, cdr, list ... which it turns out we can combine in all sorts of ways. Some of which are more "standard" in lisp than others.

We'll work through some examples in class.

Some other places to read about this stuff :

• MIT scheme reference: lists
• simply scheme: lists

related: null?, '(), pair?,

coming: map, filter, accumulate, ...

possible class exercise :

• create a tree data structure
• write a function to count the number of elements in that tree
• write an API to create and access such a tree

your turn

... to continue working through the book & the exercises.

attachments

		last modified	size
	fig2_3.png	Wed Sep 15 2021 10:29 pm	132K
	lambda.png	Wed Sep 15 2021 10:33 pm	47K
	let.png	Wed Sep 15 2021 10:33 pm	45K