Lambda the Ultimate

In the context of programming languages, why distinguish types and classes? People seem to use these two terms interchangeably. Is this because there is no or little difference, or this is by mistake?

I am interested in differentiating between functions with side-effects and functions without side-effects in a type-system. Does any suggestions on papers I should read, or keywords I should search for? [Edit: apart from monads]

Thanks in advance!

I'm looking for LISP (or Scheme) implementations for mobile devices (Symbian, Linux, Windows Mobile, etc.). Is anyone aware of any projects or vendors who cover this area?

This link describes an implementation of dimensional analysis in C++ using the Boost MPL. What this means is that physical quantities have a type parametrised by a tuple of integers representing the order of physical dimension (i.e. mass, length, time, etc...) with rules determining what operations can be carried out. This is a standard sanity check for equations in physics and easily catches typos.

For example the equation for the force acting on two massive bodies is G(m₁m₂)/d². If this were accidentally entered as force f = G*(m1+m2)/(d*d) (perhaps due to misremembering the formula) the compiler would throw a type error.

This is clearly a useful techniques for say, rocket guidance systems. What other languages are capable of doing this without having to declare a morass of types and functions relating those types to each other?

The use of automata theory seems to conflict with the notion of "software". This may account for why automata theory is rarely mentioned in computer science or even in software engineering. Imagine my surprise when I came across these two recent whikipedia entries:
Automata-Based Programming , and Switch Technology .

I found this http://weeklysqueak.wordpress.com/2007/02/15/complete-computing-system-in-20k-lines-of-code/ which includes links to a video, NSF project, whitepaper etc, describing the combination of Object and Functional architectures for building a programming system. Its incredibly interesting, even I I don't quite understand all the concepts yet. Has this been addressed at LtU? I searched but didn't see anything.

Hi Folks,

In writing some lisp code for uni coursework ("bin-packing" EA problem), I've encountered some weird behaviour. I copy a list, containing an element of type 'item', and attempt to set a value on the copy only. The code below is a modified excerpt but displays what I mean - I expected the 'container' in X to be 0, and its equivalent in M to be something random, but both elements get set to the same random value.

(defstruct item
id
weight
type
container)

(setq X (list (make-item
:id 0
:weight 0
:type 0
:container 0)))

(setq M (copy-list X))
(setf (item-container (nth 0 M)) (random 50))

I'm fairly new to lisp, so I'm not sure if this is correct or not (I suspect that it is, since clisp and emacs lisp behave the same way). Can someone point me in the right direction?

edit: Adding my solution for anyone googling for a similar problem:
(defun copy-item-list (s)
(if s
(cons (copy-item (car s))
(copy-item-list (cdr s))))
)
Good shout, johnwcowan.

Today's xkcd is about Lisp. I busted out laughing at the second panel. Thought you might be interested.

A question from the: "You can do my homework!" department.

Since I am an avid lambda reader, and given the recent thread on why people don't use functional programming, I thought I might ask for assistance from the lambda-crowd with a particular problem I have.

These days I am coteaching a Flash course. The language used in Flash is actionscript, which is a javascript derivative, which is a Lisp derivative.

Therefor, Flash might be an excellent aid in teaching functional programming.

However... At the moment my imagination kind of falls short in what kind of interesting examples one could use in a course. I thought about some calculator to showcase closures, or some functional spreadsheet implementation in Flash. They seem boring to me.

So, how would one teach functional programming in Flash, and more to the point: What kind of examples would one use?

Cheers,
Marco

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