When comparing Pyret vs Rebol, the Slant community recommends Pyret for most people. In the question“What is the best programming language to learn first?” Pyret is ranked 50th while Rebol is ranked 51st. The most important reason people chose Pyret is:
You can use the development environment without installation in your browser and share your programs via the Google Drive integration.
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Pros
Pro Online IDE
You can use the development environment without installation in your browser and share your programs via the Google Drive integration.
Pro Designed for education
A primary goal of Pyret is to be an excellent choice for a first programming language. This heavily influences the development of the language. For example: if it's felt that some aspect of the language could be made better for the language's users, The development team won't hesitate about implementing breaking (non backwards compatible) changes into Pyret for the greater good of the language. This makes Pyret an impressively "wart free" programming language.
Pro Very simple syntax
Rebol's name came from "Relative Expression Based Object Language". Rebol is a functional language and everything is an expression that returns a value. Things that have to be baked into the grammar in other languages are simple function calls with block arguments in Rebol.
Pro Homoiconic
Code is data, and data can be code. Rebol is based on a simple block data structure, used both for data and for the code itself. Blocks can be manipulated programmatically, and then evaluated as code. This makes metaprogramming easy in Rebol.
Pro Human friendly
Almost natural language, for example: write %out.html read http://google.com
.
Pro Graphical user interface
Beginners are usually stuck making command-line applications in other languages, because GUIs are too hard. Rebol GUIs are easy enough to start with.
Pro Domain specific languages
Rebol's simple homoiconic syntax makes it easy to create "Rebol dialects"--domain-specific languages optimized for a particular purpose. The Rebol distribution includes many of these, and users are free to create more. These DSLs make tasks that would be complicated to express in other languages easy.
Cons
Con Missing IDE features
For example: content assist, go to declaration, etc.
Con Not (yet?) Free Software
Rebol 2's core is free (gratis) for commercial use, but the license prohibits modification, a violation of the DFSG. Rebol 3 is Free Software (Apache 2.0), but isn't production ready.
Con Very niche language
Small community.
Con No separators
A function call expression has no parentheses, and there are no separators between sequenced expressions, not even newlines. This means that you have to know the arity of every function in an expression to know how to parse it. It also means you can run into subtle, hard-to-find bugs if you don't provide enough arguments, since the result of the next expression will be passed instead.
