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Archive for February, 2008

29 Feb 2008

by Noel

Announcing: Instaservlet

We’ve just released a package called Instaservlet, which enables you to get a servlet running in two lines of code, plus the servlet code. Here’s a simple example:

  (require (planet "" ("untyped" "instaservlet.plt" 1)))

(define (servlet request)
'(html (head (title "It's working!"))
(body (h1 "Instaservlet is in the house!"))))

(go! servlet)

Try it in PLT Scheme 3.99 and see!

This package arose out of the development work I did on Smut Shorts, which made me I realise we needed to support a quick start for web development. Instaservlet is the first step in doing this. Not only does it setup the servlet, it does it in a robust manner. Continuations are managed using the LRU manager, which can be a bit difficult to setup but it much more robust than the time-out manager. Instaservlet uses some sensible defaults which should work for most small to medium size sites — they’re the setting used on Smut Shorts, so we know they can handle a reasonable load. It also sets up a nice default page to handle continuation expiry. Instaservlet is good enough to get you started with, and future versions will enable more customisations so it can scale to any website build using PLT Scheme.

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22 Feb 2008

by Noel

Naming Your Wireless

From my study I can pick up about six different wireless networks. They all have simple names: the name of the router (good oldBelkin54g is always up and always open), the street, the owner. But in West Hollywood that is not the way they roll. How aboutfuckyougetyourownnetwork, or my favourite,Lesbian_Dildo_Vagina_Party? Is this a cultural thing? In all my time in the UK I’ve never seen a network with names like those. On the other hand I am pleased to see one of the networks is named after me. What are the networks around you called?

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15 Feb 2008

by Noel

Requiring up and down syntax levels

If you do any macro programming in PLT Scheme you are sure to run into the dreaded “no #%app syntax transformer is bound” error message at some point. Though puzzling, the fix is actually quite simple in almost all cases. Assuming you’re using 3.99, you either need to:

  1. (require (for-syntax scheme/base))
  2. (require (for-template scheme/base))

What the error means is that some syntax has expanded in a function application, but #%app, the PLT Scheme primitive that actually handles application, is not bound in the phase in which the syntax is being evaluated. Requiring for-syntax will bind #%app in the phase before the current evaluation phase, while requiring for-template will bind #%app in the phase after. In most cases you wantfor-syntax. However, if you are writing functions that return syntax that is then inserted into a program (such a function would be required for-syntax elsewhere) you must use the other form, to make sure the syntax has #%app available to it.

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14 Feb 2008

by Noel

Happy Valentine’s from Untyped

For Valentine’s Day we have created a new website,<a
href=””>Smut Shorts. If you have
something to say about love or lust, and can do so in 500
characters or less, then please add it to the growing number
of “shorts”. It’s anonymous and fun. Just, no
porn thanks.

If you’re reading this site, you’re probably interested
in the technical details behind Smut Shorts. It is a
collaboration between a number of people, most of whom have
chosen to be anonymous. The majority of the coding was done
by yours truly, and therefore in Scheme. It is running on
the PLT Scheme webserver (version 3.99) and uses PostgreSQL
as the back-end. I coded it up in about two days. It was a
side-project, so it was a bit of rush job and there is lots
still to do. If you break the site let me know and I’ll try
to fix it.

A few interesting lessons were learned from doing this
site. It all comes down to scalability, which is something
that has recently been on my mind a lot. In this case we
want to scale down to the low end — the guy who is
just hacking up something in his spare time and wants to get
it done in a hurry. Our frameworks, Snooze and Lylux, are
pretty good but they don’t support a fast start. You have
to create a whole bunch of files before you’ve even got your
first page up. Furthermore, we’ve always avoided creating a
templating mechanism, as we’ve said that we’d rather use
smart people who can balance parens than create this
unnecessary divide between designers and programmers. I now
recognise this is a mistake. Had we a templating mechanism
I could have pushed more design work to my collaborators.
It’s not that they’re stupid (far far from it) but they’re
busy and don’t have time to learn even Scheme basics just so
they change a few lines of text. If we’re gonna grow the
Scheme web-hacking community it has to start with dudes
messing around in their spare time, so we need to address
the low-end of scale. The high end of scale can wait till
the IPO ;-)

Posted in Web development | Comments Off on Happy Valentine’s from Untyped