Re: good books on scheme?

[Michael Bogomolny <bogo@bigfoot.com>]

a lambda expression (i.e. a procedure definition) returns a *closure*,
capturing the environment in which it was defined so that it can
execute in that environment when called.

example:
(define (make-counter)
  (let ((x 0))
     (lambda () 
        (set! x (add1 x))
        x)))

make-counter returns a procedure that, when called, increments the
value of its local variable x each time. Several procedures can be
defined using make-counter, but each one has access to its own local
x.

> (define counter1 (make-counter))
> (define counter1 (make-counter))
> (counter1)
1
> (counter1)
2
> (counter2)
1
> (counter1)
3


if you like "The Little Schemer" you should probably check out
"essentials of programming languages" by Daniel Friedman, Mitchell Wand, and
Christopher Haynes. A new edition was just released by MIT Press. I
haven't had a chance to evaluate it yet, though, so I can't comment on
it's quality.

>From a teaching perspective, Concrete Abstractions (Hailperin, Kaiser,
Knight; Brooks/Cole Publishing Company) and Simply Scheme (Harvey and
Wright; MIT Press) are both good books. However, they both fail the
"closure test". Interesting enough, Essentials of Programming
Languages *does* have it listed, though.

Also failing the "closure test" is the r5rs standards!

-bogo


On Feb 06, 2001 11:59, Tim Hanson wrote:
| hi, I read SICP a number of years ago and was mostly delighted, in stark
| contrast to a number of unimpressed reviewers cited in this space in the past
| couple weeks! :)
| 
| my scheme skills, however, have atrophied considerably in the past few
| years, during which time I've been paid to do more "scripting" using ksh, awk,
| perl, and more recently MS's "windows script host" and "active server pages."
| 
| i tried to follow a recent discussion which mentioned tail recursion and
| closures. i remember tail recursion from SICP, but had forgotten what a closure
| is and I didn't find it in the index of my old copy (nor in the index of "the
| little schemer", the only other book on scheme I have. ah, wait! the latter
| has "apply-closure" and I find what I wanted to know: a closure is "a
| non-primitive function"?)
| 
| i was going to ask: can folks recommend good books on scheme, including ones
| that define "closure." i guess I can still ask that and can also appeal to
| the authors among you to include it in the index in your next editions! :)
| 
| cheers,
| 
| Tim Hanson
| 
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