On the first pic you see me sitting outside being cold on a bench next to Phillipe Mougin - he wrote FScript - a Smalltalk compatible scripting language that sits atop ObjectiveC objects. Sort of like what BeanShell is to Java. I had integrated FScript into CLIPS (the expert systems shell) to provide a sort of ObjectiveCLIPS expert systems shell with scripting. One of these days I plan to package it with a UI for Mac OS X.

Anyhow, I wanted to show it to Phillipe (since this was the first time I had met him but had been using his work for awhile) and I had started an architectural change to it a few days before and it was broken.

What you see is me madly trying to get it into a working state.

OT - how it works

Fun stupid hack - clips interpreter lets you register a function pointer under a name to use in the scripting language. So a call looks like (func arg1 arg2 arg3).

Typical smalltalk syntax for a code block is to put it in square brackets [ ].

My hack registered the glue code that calls into FScript under the name '['. So it looks like the interpreter totally supports FScript natively.
ie ([anObject doSomething])

"Does it add to the interpretation time? Or is it basically transparent?"

The glue code? Its no worse than any other built-in function in CLIPS. The whole interpreter is a base parser with plugins. A bunch of the plugins are "built-ins" but that just means the default initialization code registers those plugins. The mechanism is the same regardless. A function can also register a parser function - or not. I register one that takes over until the closing bracket, pops that off the stream and then gives back control after marshalling/binding and calling FScript.

So its basically transparent. Phillipe was amused. I need to clean up the object-to-fact mapper before releasing it to the world.

in Smalltalk is an object of type SystemDictionary named Smalltalk. So, if you want to get hold of the object that represents the String class you could do something like:

(Smalltalk at: #String) compile: 'becomeRaspberry self become: ''ppppppppppppp'''.

Or something like that.
Which would add a method becomeRaspberry to the String class.

The VM is written in a subset of Smalltalk called Slang. This makes it really easy to debug the VM - because the debugging tools in Smalltalk are second to none.

There is a translator that tranlates this into C. The C makes very few assumptions about the underlying OS. A few glue routines need to be written to get mouse, keys, blit bits, network, time functions, file IO. Starting from zero, it takes about a week to create a new VM for a new platform. Fortunately for you, windows is already done (as is classic Mac, OS X, Linux, the commercial unices, and some palm tops).

The VM is launched with an "image" file. The image is basically a dump of memory. There is also a sources file and changes file that squeak needs for development. All code changes are logged.

You can file in or file out code from the image. But the image is a sort of garden of live objects. You don't so much write programs as put objects together and they just are. They live in the image. Saving the image is snapshotting your machine. You can have as many images as you like.

This isn't a good way to get a job. Not directly. While Smalltalk is by far the superior language and the source of most new ideas in software (extreme programming, JUnit testing, model view controller...) were invented in Smalltalk first, then ported to the weaker languages, Smalltalk work is scarce.

OTOH, its the best environment I know of. Crank through the free books. It will bend your mind.