30.10.06. Simple Nuggets - Recent Interests in Seaside, Io, and more

I know that I haven’t posted much lately. I do have a couple of long draft pieces saved that I haven’t had time to finish. I don’t know if I’ll get back to them, but I’ll try.

I’ve been looking at a lot of different things recently, looking for new inspirations, tools, and/or chances to widen my understanding. I find myself growing increasingly fond of a couple of things in particular: Seaside on the web development side, and Smalltalk, Scheme/LISP, Io, and Javascript (particularly with the Prototype.js library) on the programming language side.

Seaside interests me on many levels. I’ve been staring at it with a lustful eye for some time now. There is definitely a place for heavily stateful web apps. Seaside and WebObjects make this a part of their core, where a developer can make an application in a style that is more like a desktop application: less dealing with sessions, freedom from the typical request-response cycle, etc.

But Seaside is more than continuations and callbacks. I love how you generate HTML in it: NO TEMPLATES!!! In a post titled “Turtles All The Way Down”, Ramon Leon writes:

Seaside lets me work in Smalltalk, at every level, all the way from programmatic generation of the HTML and Javascript to configuration of the application. No HTML, XML, XSLT, or SQL is necessary to build a web application, just simple, pure Smalltalk. Programming’s never been more fun!

I’ve made some in-house tools that get us closer to that goal when using Zope 3 and Python. I’ve started to hate template languages again. Well - I don’t mind using them for layout intensive work. But as I get more proficient with CSS, even that is changing.

[Edit: Moved side rant about Zope and Views and Templates out... This isn't the post for it]

It still stare lustfully at Seaside code, especially things like this very basic example:

renderContentOn: html
    html heading: count.
    html anchor callback: [self increase]; text: '++'.
    html space.
    html anchor callback: [self decrease]; text: '--'.

Ooo. Two links are made with anonymous functions that call self increase and self decrease respectively. There’s no “absolute URL”-ness going on. There’s no “how do I make it so that increase can be called through the web?”. No exposure decorator. No seven lines of XML code each for ‘increase’ and ‘decrease’ to be made into separate views. And no template. Just a solid binding between a link on a form and real code.

Seaside is a testament to the power of Smalltalk. People think that Seaside is all about continuations, and if they get just that part down, they’ve made something to compete. But it’s more than that: Seaside is a tool for building web applications in pretty much the same way one makes a desktop application. It’s not the tool or style for every job, but it definitely has its place.

In a recent bit of work we've done in Zope 3, I would have loved to have something like Seaside, especially for the checkout process. I've tried to engineer that process as well as I could, with extra preconditions and redirectors on pages to ensure that all desired information is supplied (ie - so that one can't jump from step 1 to step 4). With Seaside I could have encompassed the in a WATask component, expressing the checkout workflow as normal Python code: while shippingAddressRequired and (not order.shippingAddress): yield self.askForShippingAddressForm() (or something like that). The shopper could never accidentally (or purposefully) get past that point without supplying the right information. Doing this with preconditions, sessions, hidden form fields, cookies, etc, is all possible. But it can be a lot more code overhead.

Back to the other interests listed, really quickly: I’ve used LISP on very rare occasions (for customizing EMacs, basically, back in the day). I’ve never quite understood the appeal that LISP / Scheme have for some people until recently. While I enjoy and will probably continue to work in general purpose languages like Python, I’ve started to grow fond of these languages that are built on very simple precepts. Smalltalk has practically no syntax: it’s all messages. And I really like that Squeak is written in itself - there’s just something impressive about that. On a related topic, I checked on the progress of PyPy and was very impressed. Like Squeak, which has a small subset-of-smalltalk-to-C translator for generating the core pieces from Smalltalk itself, PyPy is Python written in Python, with translators to lower-level languages.

Regarding Scheme, I found a Scheme translator for Smalltalk and have spent a small amount of time playing with it this weekend. I came away impressed with how easy it is to parse and process Scheme, and how easy it is to implement it and its primitives in quite easily readable Smalltalk. The “everything is a list” (‘car’ and ‘cdr’) power finally came through to me as I browsed through the Smalltalk code to see how things that are keywords and operators in other languages (‘+’, ‘if’, etc) were implemented by just using car and cdr (the head and remainder of any list/pair, on which all things are based).

I’ve also become very interested in prototype-based programming. With prototype based programming, one has Objects but without classes and metaclasses and on and on. I’ve known about prototype based programming for some time, but I’ve only recently started to appreciate it. It’s radically simple. Looking around at Prototype based languages, I came across the relative newcomer Io. Io has no keywords - which, again, I find quite interesting and provocative. And powerful. It’s message based, which I like, and it has no classes. You just clone something to make something else. A simple object example from the sample code page:

Account := Object clone do(
    balance := 0
    deposit  := method(v, balance = balance + v)
    withdraw := method(v, balance = balance - v)
    show := method(writeln("Account balance: $", balance))

myAccount := Account clone
myAccount show
"Depositing $10\n" print
myAccount deposit(10)
myAccount show

Oh yeah - and the minimalist in me swoons over its web site.

There it is - a scattering of a portion of the thoughts that occupy my brain when I have the chance to take a breath at work.