I've just started to read about Ruby, and I was wondering if it can be embedded in a C++ application like Lua which provides a library to parse a given script file: https://stackoverflow.com/a/5127294/399107
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3Out of curiosity, since I'm biased towards Lua ;). Why do you prefer Ruby?W.B.– W.B.2013-05-15 11:57:43 +00:00Commented May 15, 2013 at 11:57
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3 Answers
Yes, you can. You just need to embed a Ruby engine in your application.
Note that, unlike the main Lua engine, some Ruby engines aren't really that well suited to being embedded into other programs. But, for example, Rubinius, IronRuby and JRuby have been specifically designed with embedding in mind, and even though it isn't pretty, you can embed YARV or MRI as well, even though they are not designed for it.
There's also MRuby, but unlike the others, it doesn't implement the full Ruby Language Specification, it only implements a subset of the ISO Ruby Specification which itself is only a small subset of the intersection of Ruby 1.8 and Ruby 1.9. Plus, it hasn't been released yet, as is evidenced by the fact that not even its homepage exists yet. It is, however, specifically designed for embedding, in both senses of the word: being embedded into other programs, and being useful on an embedded device with very little RAM.
As you may have noticed, it is much easier to embed Ruby into your app if the app is running on the Java platform or the CLI. There are C++ compilers for both the Java platform and the CLI, so that option is not entirely out of the question. Otherwise, I'd say that Rubinius is easier to embed, but more people have tried embedding YARV, so there are more blog posts about how to do that. (Or maybe, embedding Rubinius is so trivial nobody needs to write blog posts about it.)
A long time ago, someone was working on an implementation of Ruby for the Lua VM, but that implementation never went anywhere. Would solve all your problems, though :-)
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nosferat
Very detailed answer! However I'm getting more and more concerned that Ruby is not suited for my purposes.
radiospiel
I might be a bit late to the party; but still want to extend Jörg's response by adding that embedding ruby is probably a security nightmare, if you do not control the scripts to be run. While lua does not have a standard lib to speak of and so can only do what you explicitly expose to it, Ruby comes with its std library, which allows all number of things, including reading and writing files and interacting with the internets. Depending on your use case this might be cool or ultimately dangerous.
Sure you can. It's possible with with SWIG, or you can make your own bindings for it (or google to see if someone has already done the work). The big question is do you really want to? The ruby interpreter is pretty heavy, and the interface isn't very nice.
Matz is working on an embeddable version of Ruby called mruby, which strives to be as easy to embed and as light as Lua. But its still alpha quality.
1 Comment
nosferat
Well if the interpreter has a significant cost, then Ruby is not the best option for me. That's sad I liked what I read about it so far.
Yes, it's possible. Most of the standard libraries types are written in C. And when you can use C, you can use C++ too. Use extern "C" declared functions to get the right binding. I had a lot of trouble, when using a C++ compiler that was different (different version) from the compiler that was used to compile the ruby interpreter.
Here is the part of the pick axt book, that covers the ruby extension library: http://media.pragprog.com/titles/ruby3/ext_ruby.pdf
In an open source C++ web server project, I wrote a ruby / rack adapter, to use the server with rails: https://github.com/TorstenRobitzki/Sioux/tree/master/source/rack
