When comparing Lua vs Rebol, the Slant community recommends Lua for most people. In the question“What is the best programming language to learn first?” Lua is ranked 16th while Rebol is ranked 51st. The most important reason people chose Lua is:
One of the best features of Lua is its very well designed C API. This is very useful if you have an existing C library you need to integrate with Lua or quickly get a Lua script running on the C side of the game. Finally Lua plays so nice with C that if you need to optimise for speed you can re-write it in C a lot easier than other languages.
Specs
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Pros
Pro Very easy to integrate with C and C++
One of the best features of Lua is its very well designed C API. This is very useful if you have an existing C library you need to integrate with Lua or quickly get a Lua script running on the C side of the game.
Finally Lua plays so nice with C that if you need to optimise for speed you can re-write it in C a lot easier than other languages.
Pro Great documentation
The official Lua documentation is very helpful and thorough. There are also a large number of online resources or books with lots of helpful information for beginners and advanced users alike.
Pro Portable
Lua can be built on any platform with a ANSI C compiler.
Other than that, Lua is extremely small. For example, the tarball for Lua 5.2.1 is only 245K compressed and 960K uncompressed (including documentation).
When built on Linux, the Lua interpreter built with the standard libraries takes 182K and the Lua library takes 243K.
The small size and the ability to build with a C compiler make Lua an extremely portable language that can run on a lot of different systems and computers.
Pro Simple
Easy to learn.
Pro Fast
Lua's performance compares very well to other languages, If performance needs to be further improved you can:
- Implement critical parts in C
- Use the LuaJIT compiler. The LuaJIT compiler is a drop in replacement for the stock compiler and provides significant performance improvements. From the overview page:
LuaJIT speeds can rival code written in C.
Pro Embeddable
Many different game engines (e.g. Elder Scrolls series, ToME) use Lua for scripting, and it's runtime is designed for embedded use.
Pro Clean and simple syntax suitable for beginners
The Lua syntax is modeled from Modula, a language known for being a fantastic introduction to programming.
The Lua syntax also has the following key characteristics:
- Semicolon as a statement separator is optional (mostly used to resolve ambiguous cases as in a = f; (g).x(a)).
- Syntactic sugar for function calls (f'string', f"string", f[[string]], and f{table}) and method calls (obj:m()).
Pro Helpful community
Due to the growing popularity, Lua has a rather large and helpful community surrounding it.
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 Easy to make mistakes when declaring variables
When writing a function, if a programmer forgets to declare a variable, that variable will be declared at global scope. The code will seem to run fine at first, but if another function uses a variable with the same name, but fails to declare it, it will create subtle, incredibly difficult to find bugs.
Con Some concepts may not be applied to other "mainstream" programming languages
Lua features a prototye-based inheritance model. While this is also used by Javascript, it's not used by many other mainstream languages, and so some of the concepts learned while learning Lua won't be very applicable to other languages.
Another thing that makes Lua different from other programming languages, is the fact that Arrays start at 1 instead of 0. While helpful for beginners, it can complicate logic and make it very confusing when switching languages.
Con Batteries not included
Lua is so small mainly due to many of the components not being included in the core package. A lot of people need the functionality provided by the Lua module management system LuaRocks and libraries such as Penlight.
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.