(archive 'newLISPer)

January 30, 2008

Welcome Arc, a new LISP!

Filed under: newLISP — newlisper @ 17:55

Congratulations to Paul Graham and Robert Morris on the birth of their new Lisp language, Arc. It’s great to see another new Lisp addition to the family of Lisp.
I liked these quotes:

Arc is designed above all for exploratory programming: the kind where you decide what to write by writing it. Exploratory programming is the fun end of programming.

It’s not for everyone. In fact, Arc embodies just about every form of political incorrectness possible in a programming language.

It’s not a coincidence that we wrote a language for exploratory programming rather than the sort where an army of programmers builds a big, bureaucratic piece of software for a big, bureaucratic organization.

newLISP encourages experimentation and exploration, and that’s made possible by the rich built-in function library, the design of the language, and the involvement of the newLISP community. I built the blogging engine that you’re reading now by exploring and trying out ideas, and not being too concerned at first with the theoretical niceties of functional programming. I think that newLISP encourages that approach, as well as allowing for more serious programming.

I suspect that Messrs Graham and Morris would be very happy if people like me – not just Common Lisp initiates – were able to do the same thing with Arc.

Good luck, Arc!

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January 12, 2008

Lambdalator: the story so far

Filed under: newLISP — newlisper @ 16:20

One of the fun things about my current experiment, the Lambdalator (a simple script that provides the internet with a 24/7 online newLISP console) is that I left a call to the following function in the script. I’d used this function when I’d first uploaded the script for testing:


(define (log-input x)
    (append-file log-file-name
        (string
            (date
                (date-value) 0 "%Y-%m-%d %H:%M:%S") { }
            (get-ip) { } x "\n")))

So whenever anyone types anything and clicks the ‘evaluate’ button, the date, time, their IP address, and what they typed are saved in a log file. So by looking at the log it’s more or less possible to watch people arrive, enter stuff, get annoyed, and go away. This has provided a lot of entertainment – and some education – over the last few weeks, and I’ll share some of it here.

2008-01-03 18:40:20 163.453.357.176 hello

(All IP addresses have been scrambled in this post.)

The big drawback of the Lambdalator is that, as with any programming language, if you don’t get the format exactly right, the result will be, at the very least, unexpected. newLISP doesn’t pretend to understand English, and the Lambdalator isn’t an exercise in artificial intelligence or natural language parsing. It’s just a simple online calculator-style utility expecting expressions using newLISP syntax; there’s only 100 or so lines of code, and a chunk of that is HTML.

But I wish I’d added some extra code to handle input like this:

2008-01-03 15:06:48 33.453.30.235 how are you doing?
2008-01-03 15:07:14 33.453.30.235 What is the purpose of this?

or to respond to ‘calculations’ like this:

2008-01-03 12:08:24 84.43.89.37 Today I am going to work very hard

2008-01-04 21:48:59 93.453.398.228 sausages

2008-01-05 10:08:23 63.453.31.191 poop

Of the people that have actually tried to use it as a calculator, many have of course been thrown by the postfix notation, the compulsory parentheses, and the need for white space to separate functions and arguments. With no knowledge of what should be typed, and a reluctance to click the ‘help’ button, newLISP’s responses are entertaining, enigmatic, irritating, or just baffling. Here are some examples – I’ve added the Lambdalator’s replies so that you can sympathize – or not – with the questioner:

2008-01-06 22:43:06 83.453.359.133 (+22)
invalid function : (22)

2008-01-05 18:28:54 153.453.38.114 (+2 2)
illegal parameter type : 2

2008-01-04 12:42:33 63.453.381.231 (2 -3 2 2 6)
illegal parameter type : -3

2008-01-06 19:46:23 76.73.453.332 + 2 2
2

2008-01-06 21:11:36 73.453.303.239 61-8
-8

2008-01-05 04:01:22 166.70.39.75 add 5 65 46
46

2008-01-05 02:42:53 33.453.39.213 2*5
nil

2008-01-04 12:41:39 63.453.381.231 4 plus 2
2

2008-01-03 13:28:50 33.453.332.66 cos(x) + sin(y)
invalid function : (x)

2008-01-07 03:56:41 32.423.242.38 ( 6% of 70)
illegal parameter type : %

Many were confused by the fact that the Lambdalator returns the value of the last expression evaluated, but only the last. So + 2 2 returns the last 2 – not the expected sum.

Here are some optimistic entries, where people have expected more from my efforts than I could deliver:

2008-01-03 15:18:06 143.453.329.143 2x+3=40
nil

2008-01-03 15:18:48 143.453.329.143 x=2y+4
nil

2008-01-05 16:52:29 85.59.94.226 56+33*x=0
nil

2008-01-04 12:39:08 73.453.33.175 x2\y=9
nil

2008-01-03 05:29:36 68.73.453.30 1+x=9
nil

Luckily newLISP refrains from offering an opinion on such weighty matters. One day I’ll write something that solves equations.

Some people have a different idea about what parentheses are:

2008-01-03 18:06:31 68.453.37.26 [2.3]+{4[6.3]}
nil

2008-01-04 13:21:50 193.453.355.48 [ + 2 2 ]
nil

One problem that I had anticipated is that in newLISP the standard arithmetic operators such as ‘+’ and ‘-‘ are integer only, and you use the ‘add’ and ‘sub’ equivalents for floating-point operations. I’ve got used to this, and there’s an easy way to re-define ‘+’ to do the job of ‘add’, but I decided to keep the behaviour as close to the documented default as possible. But it’s a pity that a good attempt like the following should have received the wrong answer:

2008-01-08 00:01:49 75.453.32.16 (+ (+ 1.234 91.3) (+ 1.234 91.3))
184

A few Lisp speakers have visited the site, and they obviously know the basics, although the whole thing is probably much too simplistic and toy-like for the Common Lisp folks. I seem to remember that ‘car’ is the equivalent of newLISP’s ‘first’ function, and it’s obviously a favourite (but not available by default in newLISP):

2008-01-07 03:25:17 72.453.32.16 (car '(a b c))
invalid function : (car '(a b c))

2008-01-03 19:40:50 83.453.305.64 (car (cons 1 "a" 3.45  'foo))
invalid function : (car (cons 1 "a" 3.45 'foo))

2008-01-07 03:25:01 73.453.32.16 (cons '(a b c))
((a b c))

2008-01-10 20:41:37 63.453.379.30 (foldr list 'end '(a b c d))
invalid function : (foldr list 'end '(a b c d))

I’ve not heard of ‘foldr’.

But here’s a fun entry that set me thinking:

2008-01-10 20:47:45 65.453.379.30 (apply (lambda (x) (* x 2)) '(1 2 3))
2

Why does this return 2 – and not 6, for example, which I might have expected, although I would have used ‘map’:

(map (lambda (x) (* x 2)) '(1 2 3))
(2 4 6)

The other big drawback with the whole idea of the Lambdalator is that it’s not possible to have a persistent newLISP interpreter online in this way. Well, it’s probably possible, but I know that my current host doesn’t allow persistent processes, and I expect there are other issues to think about. At the moment the web page gives the illusion of some persistence, with the ‘paper tape’ feature of a typical desktop calculator keeping a record of what’s been processed, but of course in reality every time an expression is submitted a new session is started with no record of any previous entries.

I think I’ll keep the Lambdalator online for a few more weeks, since it’s interesting to watch what people make of it, and I make use of it myself occasionally. I’ve yet to see anyone trying to hack the security, which will be interesting – and possibly worrying – to watch.

January 6, 2008

Lisp in web pages

Filed under: newLISP — newlisper @ 10:39

The next paragraph took me about an hour to write. And I didn’t write all of it.

You viewed this page on — (date) — .

The idea is that I can include some raw newLISP that gets evaluated only when the page is generated and displayed in the browser.

I stole this cool idea from Jeff’s post in the newLISP forum, and this feature is now built in to Dragonfly.

your ip address is — (or (env “REMOTE_ADDR”) (env “REMOTE_HOST”)) —

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