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Comment by TeMPOraL | Hacker News Reader

What's the difference between Snap! and Scratch? They look prima facie identical.

Scratch is a simplified version of Lisp/Scheme, without many important features like first class functions, lexical closures, continuations, special forms, the ability to define your own blocks and control structures, and everything being a first class object that you can bind to variables, pass around, and return from functions.

Snap! supports all those important features of Scheme (its original name was BYOB for "Build Your Own Blocks"), with the visual interface and sprite and stage and turtle graphics of Scratch, plus it's written in JavaScript, so it's efficient and easy to integrate with existing JavaScript libraries (see "etoys2learn"!), instead of running in a monolithic Smalltalk virtual machine.

Scratch does allow you to make your own blocks with optional input. My math students use them to learn about abstraction. The most recent implementation was released last winter and is written in JavaScript.

https://en.scratch-wiki.info/wiki/Scratch_3.0

Scratch 3 does not enable one to define new functions only new commands. Snap! user-defined functions are first-class - they can be used to define higher-order functions.

Here's the elegant Snap! visual Y Combinator:

https://imgur.com/cOq8tvR

Visual Lambda: Note how the gray block after the "report", shrink-wrapped around the "call (fn) with inputs (fn) []", is a visual "lambda". It looks like a "gasket" or "baggie" that insulates the code inside from being immediately evaluated, returning a closure instead.

Snap! takes inspiration from Scheme. I wouldn't compare Scratch to Lisp/Scheme at all, as IMO lambdas, cons-cells, and (the ability to make) expression-based control structures are all defining features of Lisp/Scheme, and Scratch does not have any of them. To my understanding, Scratch's design seems to be inspired by Kay-style OOP (Scratch's "broadcast" feature is about passing messages between sprites, and the first version of Scratch was written in Squeak).

Thank you! That answers all my questions. I'll go play with Snap! then.

BTW. you seem to know your way around these kinds of semi-visual languages; any opinion on NetLogo? A coworker recently introduced me to it, and it looks like a great tool for doing agent simulations. I wonder if you know of anything else worth paying attention to in this space?

I haven't tried it myself, but I've heard it's really cool, and have read people who've used it praising its virtues and discussing its limitations. It sounds like something I'd like, since it's great for agents and cellular automata.

NetLogo – A multi-agent programmable modeling environment (northwestern.edu)

https://news.ycombinator.com/item?id=18180542

https://ccl.northwestern.edu/netlogo/

Seymour Papert has died (mit.edu)

https://news.ycombinator.com/item?id=12201810

http://www.media.mit.edu/people/in-memory/papert

You might also want to check out some of the stuff in these papers, one pretty old, and the other much more recent:

“A Taxonomy of Simulation Software: A work in progress” from Learning Technology Review by Kurt Schmucker at Apple (1999).

http://donhopkins.com/home/documents/taxonomy.pdf

"Gadget Background Survey" by Chaim Gingold (who made Earth Primer), research he did at HARC for the Gadget project with Dan Ingalls (who made Squeak and Lively), which includes Alan Kay's favorites, Rockey’s Boots and Robot Odyssey, and Chaim's amazing SimCity Reverse Diagrams, and lots of great stuff I’d never seen before:

Gadget Background Survey

http://chaim.io/download/Gingold%20(2017)%20Gadget%20(1)%20S...

Earth Primer

https://www.earthprimer.com/

Experimental Gameplay Workshop 2015: Earth Primer

https://www.youtube.com/watch?v=qtsf3nRFfwk

YOW! 2016 Dan Ingalls - Pronto: Toward a Live Designer's Notebook #YOW

https://www.youtube.com/watch?v=if72CFsF_SY

The following NetLogo HN links didn't get as much discussion as they deserved, but here they are:

Show HN: NetLogo Implementation of Conway's Game of Life (github.com)

https://news.ycombinator.com/item?id=20074810

https://github.com/gsurma/game_of_life