When comparing DASH vs Rebol, the Slant community recommends Rebol for most people. In the question“What is the best programming language to learn first?” Rebol is ranked 52nd while DASH is ranked 53rd. The most important reason people chose Rebol is:
Almost natural language, for example: `write %out.html read http://google.com`.
Ranked in these QuestionsQuestion Ranking
Pro Default shell on Debian systems
DASH is the default shell for Debian based systems due to it speed, full POSIX compliance and low overhead.
Pro Full POSIX support
It's fully POSIX compatible, so if your script runs on dash it will probably run on all other shells.
Pro A perfect clone
It's a clone of the original System V4 Bourne shell.
Pro Fast startup
Dash has a very fast startup, this happens because the shell is started a lot of times during boot and dash minimizes the work it does during this process.
Pro Low memory usage, which matters a lot in embedded
It is designed to be very lightweight and has no support for shell specific extensions that are not POSIX.
Pro Human friendly
Almost natural language, for example:
write %out.html read http://google.com.
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 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 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 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.
Con Doesn't support all bash features
Dash does not support all bash features, sometimes called 'bashisms' unless explicitly pointed at
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.
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.