Build-Your-Own-Blocks extension to Scratch

I’ve been fond of Scratch as a first programming language for children and teenagers (particularly gifted children who may be able to program better than they can type), but have occasionally chafed at the restrictions of the language.  The designers of Scratch deliberately left out a number of common features of programming languages, to avoid confusing beginners.  The problem with that approach is that you hit a ceiling fairly quickly and have to get very creative to be able to do stuff that should be simple.

Some other programmers and programming educators felt the same way, and so designed an extension to Scratch that adds a lot of power to the language, without losing the essential simplicity of most of the language.  The new language is B.Y.O.B, for Build Your Own Blocks. It provides a way to create your own Scratch blocks to add to the existing set, using familiar Scratch scripting and editing techniques.

This adds procedures and recursion to the Scratch language in a very simple way.

The designers of B.Y.O.B. are strong fans of Smalltalk and dynamically-typed object-oriented languages, so they made all the new stuff (both anonymous arrays and code blocks) first-class data.  That means that you can pass code to procedures, assign it to variables, and so forth.  Some of the conventions (like grey borders for passing blocks as objects, rather than executing them and passing the value they return) are a bit too cryptic and are likely to confuse beginners.  But if you stay away from passing code around except in very simple ways, you may be able to avoid some of the confusion.

Very little needed to be added to Scratch to make B.Y.O.B., but the resulting language seems to have all the features needed to teach a first-year computer programming class.  It would be interesting to see a curriculum based on B.Y.O.B.

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Image may be NSFW.
Clik here to view.