UK Smalltalk User Group Meeting - Wednesday, December 29th

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Giovanni Corriga

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Dec 9, 2021, 5:11:05 PM12/9/21
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For our December meeting, Florin Mateoc will show us JsSqueak ( https://github.com/fmateoc/JsSqueak ), a JavaScript implementation of (JavaScript compiled) Squeak.

Whereas SqueakJS or TruffleSqueak are implementations of the Squeak stack VM which run the Squeak bytecodes, JsSqueak compiles all the Squeak code to JavaScript (including the VM plugins), it exports the image state as one big JavaScript storeString, and then loads them, and runs the JavaScript implemented minimal VM (mostly primitives) and the JavaScript-translated Squeak methods as one combined JavaScript application. The compiled JavaScript application can be run either in a browser or in Node.js

While JavaScript, especially with its newest additions, is a very powerful language, which allows us to implement most Smalltalk-specific features (e.g. processes/green threads are implemented using generator functions and recursive yield* for all invocations, DNU is implemented using proxies and proto manipulation, the Smalltalk parallel class hierarchy is implemented using JavaScript classes with static properties and their parallel prototypes hierarchy, weak classes are implemented using JavaScript WeakRef instances in their (weak) slots), one obvious challenge is implementing contexts.
Since we compile Squeak classes to JavaScript classes, Squeak methods to JavaScript methods (and class-side Squeak methods to static JavaScript methods), the code runs on the native JavaScript call stack, and we do not have a mapping between the JavaScript function activations and reified contexts. Nevertheless, it turns out that, by providing specialized implementations for various aspects that are implemented using contexts/stack walking in Squeak, we can actually run almost all Squeak code as-is.

Florin Mateoc ( https://fmateoc.js.org/ ) is an electronics engineer who has always loved programming and who has actually only ever worked as a software engineer.
Florin has worked as a professional Smalltalk programmer in Enfin (later called ObjectStudio), VisualAge, VisualWorks, and a little bit as a hobbyist in Squeak.

This will be an online meeting from home.

If you'd like to join us, please sign up in advance on the meeting's Meetup page ( https://www.meetup.com/UKSTUG/events/282445345/ ) to receive the meeting details. Don’t forget to bring your laptop and drinks!
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