I want to bind a different programming language to the Godot game engine. Is there an instructional document or video on this topic? For example, how was this project done: godot-rust. If I can learn the basics, I can succeed in working in a different language. Thanks.
In this answer I show you the different approaches to add language support in Godot 3.x (the situation will be somewhat different with Godot 4.0 and GDExtension - which replaces GDNative and hopefully means less custom builds), and I mention some languages that are supported by each of these approaches. However, this is not an exhaustive list of the languages.
First of all, Godot has official build-in support for GDScript and Godot's VisualScript (and Godot's shading language and its visual counterpart if those counts for you).
There are a few ways to use C++:
You can use it to create GDNative scripts (which are basically a wrapper around native calls that allow you to use them as scripts in Godot).
Or you can create modules (which are static libraries you can add in a custom Godot build).
And since Godot source is in C++, you don't have to restrict yourself to making modules if you are making custom builds.
In web builds Godot can interface with JavaScript via the JavaScript class. However, this approach does not allow you to add JavaScript scripts to Nodes, and so on.
Then there are languages that can only be added in custom builds of Godot, which is currently the official support for C#.
There are other non-official custom builds that offer language binding for languages such as Lua, Kotlin, TypeScript and JavaScript (this time allowing you to make scripts).
If you need to add a runtime, you would probably do this.
Some language take advantage of the fact that Godot's has official Mono support in order to support C#. This way you can, for example, use F# and Clojure.
They start by adding a C# project and then modify it so it uses another language. This is viable if your language already compiles to .NET.
Some other languages can be added as plugins that implement the PluginScript class via GDNative. This is the case of Python and Lua (again) which you can get from the asset library.
This is the most user friendly way to add language support to Godot, but it is limited to what you can do with PluginScript.
Addendum: Gil Barbosa Reis, author of the aforementioned Lua bindings, has an article series about its implementation stuffed away in the repository (in English and Portugueses): godot-lua-pluginscript/extras/articles/. It is probably the most comprehensive tutorial to date.
Other languages are added by means of taking advantage of GDNative (They basically mimic what you would do with C++). This is the case of Nim, Rust, D, Haskell, Go, Swift…
So that's how godot-rust works: make native libraries using rust and the godot-rust create and add them as if they were made in C++. For any language for which there are the means to make native libraries already, this is a good option.
Finally there is another way to add support for a language: a transpiler from that language to GDScript, which can be automated with an addon that might also be written in GDScript. This is the case of Lisp.
This last approach is mostly used for domain specific languages.
The official docs here provide your answer:
Godot officially supports GDScript, C/C++, C#.
Some 3rd party languages that can be used are: Rust, D, Python, Nim, and Go.
Is there a programming language that doesn't compile, but rather just translates into another language? I apologize if this is a stupid question to ask, but I was just wondering if this would be a literal shortcut in creating a programming language. Wouldn't it be easier (probably not speedy) but still doable?
Is there a programming language that doesn't compile, but rather just translates into another language?
That makes no sense to me. My definition of compilation is "translating from one language (the source language) to another (the target language)".
Usually the source language is something written by humans and the target language is machine code (or asm), but that's not a requirement. In fact, many compilers are structured as multiple layers, each translating to another intermediate language (until the final layer emits code in the target language).
And it's not directly related to a language, but a particular implementation. We can take C, for example: There are C interpreters, C compilers that target assembler code, C compilers that target machine code (of various platforms), C compilers that target JavaScript, C compilers that target Perl, etc.
As for simplifying the implementation of a language: Yes, there are various kinds of code reuse that apply.
One way is to separate compiler front-ends (translate from source language to an internal abstract representation) and back-ends (translate from the internal abstract representation to machine code for a particular platform). This way you can keep the front-end and only write a new back-end if you want to support another target platform. You can also keep the back-end and only write a new front-end if you want to add support for another source language.
Another way is to use a full-blown programming language as the intermediate representation. For example, your new compiler might produce C code, which can then be compiled to machine code by any C compiler. The first implementation of C++ did exactly this. C has a number of drawbacks as a compiler target language; there have been efforts to create languages better suited for the task (see e.g. C--, which is used internally by GHC (a Haskell compiler)).
Today the most commonly translated language is JavaScript. The newer constructs of ECMAScript are translated to the old version to be compatible with older browsers. The translation is done by Babel.
There are also other languages like TypeScript and CoffeScript that are translated to JavaScript.
f2c translates Fortran 77 to C code. So it is probably an example for what you are looking for.
All general-purpose programming languages are Turing complete. That means any one of them can be translated into another.
When creating a new programming language, many designers often have their first prototypes translate their new language into one their are familiar with. This makes it easier to check if the translation is correct, that the new language is working correctly, and to share ideas with colleagues since it is machine independent.
When their design becomes stable, they make a front end to an existing compiler to do the compiling. Using an existing compiler has several advantages. Optimization is instantly available. The new language can access existing libraries. Compiling can be targeted to all the existing back ends, making the language available on different architectures.
Yes, this is one technique for creating new languages. The first experiments in what became C++ were translated to C for compilation. Taken from http://wiki.c2.com/?CeeAsAnIntermediateLanguage:
Examples of using C in this fashion:
CeeFront; the original implementation of C++, translated to C.
Comeau C++ (http://www.comeaucomputing.com/) translates C++ to C. It
is the first C++ compiler to provide full core language support for
standard C++.
Several Java-to-C translators out there (some translate Java source;
others translate JavaByteCode to C)
Many experimental language compilers use C as a backend, rather than
emitting assembly language directly.
SqueakSmalltalk's VirtualMachine is written in a subset of Smalltalk
which gets translated to C and fed to the C compiler. The
VirtualMachine used by Scheme48 is written in a StaticallyTyped
SchemeLanguage dialect called PreScheme which is compiled to C. (The
PreScheme compiler itself is written in full Scheme.)
Several SchemeImplementations compile to C (e.g. RScheme, Bigloo and
Chicken). These Schemes often use the technique described in
CheneyOnTheMta to provide support for ProperTailRecursion.
More recently, compilers targeting a subset of JavaScript capable of efficient on-the-fly compilation have been created - emscripten.
And if you count assembly language as well as high level languages, WebAssembly or other bytecode languages fit.
We have Bigloo.NET does anyone know of such a project that offers the same but for the Java and/or Objective-C language?
I am developing a component of a project that will also have a Windows and Apple GUI built around it. Would be nice if I could develop this component in a single language and have it compiled into the native language for the current GUI. Any ideas?
Do you know that Bigloo initially targeted the JVM, and only later the CLR? I'm assuming you do, and that it's insufficient for you. If you weren't aware:
Java code and Bigloo code can be
merged together. Bigloo functions can
call Java functions and vice-versa,
Bigloo code can use and instantiate
Java classes. Bigloo functions and
variables can hold Java values (Java
classes values). Bigloo data
structures can point to Java data
structures and vice-versa.
If that doesn't do it for you, but you still want a Lisp, Clojure is a Lisp, though neither Scheme nor Common Lisp. It shares with Scheme a single namespace for functions and variables, however, and I've found it pretty comfortable in my short acquaintance with it. Clojure is also Java --- anything you do from Clojure can be used from plain Java, and vice versa.
Maybe you could give more detail on why Bigloo doesn't work for you, and that could help us give better answers.
Schemes for the JVM: SISC and JScheme. Both are interpreters with good Java interoperability.
I see here that there are a load of languages aside from Java that run on the JVM. I'm a bit confused about the whole concept of other languages running in the JVM. So:
What is the advantage in having other languages for the JVM?
What is required (in high level terms) to write a language/compiler for the JVM?
How do you write/compile/run code in a language (other than Java) in the JVM?
EDIT: There were 3 follow up questions (originally comments) that were answered in the accepted answer. They are reprinted here for legibility:
How would an app written in, say, JPython, interact with a Java app?
Also, Can that JPython application use any of the JDK functions/objects??
What if it was Jaskell code, would the fact that it is a functional language not make it incompatible with the JDK?
To address your three questions separately:
What is the advantage in having other languages for the JVM?
There are two factors here. (1) Why have a language other than Java for the JVM, and (2) why have another language run on the JVM, instead of a different runtime?
Other languages can satisfy other needs. For example, Java has no built-in support for closures, a feature that is often very useful.
A language that runs on the JVM is bytecode compatible with any other language that runs on the JVM, meaning that code written in one language can interact with a library written in another language.
What is required (in high level terms) to write a language/compiler for the JVM?
The JVM reads bytecode (.class) files to obtain the instructions it needs to perform. Thus any language that is to be run on the JVM needs to be compiled to bytecode adhering to the Sun specification. This process is similar to compiling to native code, except that instead of compiling to instructions understood by the CPU, the code is compiled to instructions that are interpreted by the JVM.
How do you write/compile/run code in a language (other than Java) in the JVM?
Very much in the same way you write/compile/run code in Java. To get your feet wet, I'd recommend looking at Scala, which runs flawlessly on the JVM.
Answering your follow up questions:
How would an app written in, say, JPython, interact with a Java app?
This depends on the implementation's choice of bridging the language gap. In your example, Jython project has a straightforward means of doing this (see here):
from java.net import URL
u = URL('http://jython.org')
Also, can that JPython application use any of the JDK functions/objects?
Yes, see above.
What if it was Jaskell code, would the fact that it is a functional language not make it incompatible with the JDK?
No. Scala (link above) for example implements functional features while maintaining compatibility with Java. For example:
object Timer {
def oncePerSecond(callback: () => unit) {
while (true) { callback(); Thread sleep 1000 }
}
def timeFlies() {
println("time flies like an arrow...")
}
def main(args: Array[String]) {
oncePerSecond(timeFlies)
}
}
You need other languages on the JVM for the same reason you need multiple programming languages in general: Different languages are better as solving different problems ... static typing vs. dynamic typing, strict vs. lazy ... Declarative, Imperative, Object Oriented ... etc.
In general, writing a "compiler" for another language to run on the JVM (or on the .Net CLR) is essentially a matter of compiling that language into java bytecode (or in the case of .Net, IL) instead of to assembly/machine language.
That said, a lot of the extra languages that are being written for JVM aren't compiled, but rather interpreted scripting languages...
Turning this on its head, consider you want to design a new language and you want it to run in a managed runtime with a JIT and GC. Then consider that you could:
(a) write you own managed runtime (VM) and tackle all sorts of technically difficult issues that will doubtless lead to many bugs, bad performance, improper threading and a great deal of portability effort
or
(b) compile your language into bytecode that can run on the Java VM which is already quite mature, fast and supported on a number of platforms (sometimes with more than one choice of vendor impementation).
Given that the JavaVM bytecode is not tied so closely to the Java language as to unduly restrict the type of language you can implement, it has been a popular target environment for languages that want to run in a VM.
Java is a fairly verbose programming language that is getting outdated very quickly with all of the new fancy languages/frameworks coming out in the past 5 years. To support all the fancy syntax that people want in a language AND preserve backwards compatibility it makes more sense to add more languages to the runtime.
Another benefit is it lets you run some web frameworks written in Ruby ala JRuby (aka Rails), or Grails(Groovy on Railys essentially), etc. on a proven hosting platform that likely already is in production at many companies, rather than having to using that not nearly as tried and tested Ruby hosting environments.
To compile the other languages you are just converting to Java byte code.
I would answer, “because Java sucks” but then again, perhaps that's too obvious … ;-)
The advantage to having other languages for the JVM is quite the same as the advantage to having other languages for computer in general: while all turing-complete languages can technically accomplish the same tasks, some languages make some tasks easier than others while other languages make other tasks easier. Since the JVM is something we already have the ability to run on all (well, nearly all) computers, and a lot of computers, in fact already have it, we can get the "write once, run anywhere" benefit, but without requiring that one uses Java.
Writing a language/compiler for the JVM isn't really different from writing one for a real machine. The real difference is that you have to compile to the JVM's bytecode instead of to the machine's executable code, but that's really a minor difference in the grand scheme of things.
Writing code for a language other than Java in the JVM really isn't different from writing Java except, of course, that you'll be using a different language. You'll compile using the compiler that somebody writes for it (again, not much different from a C compiler, fundamentally, and pretty much not different at all from a Java compiler), and you'll end up being able to run it just like you would compiled Java code since once it's in bytecode, the JVM can't tell what language it came from.
Different languages are tailored to different tasks. While certain problem domains fit the Java language perfectly, some are much easier to express in alternative languages. Also, for a user accustomed to Ruby, Python, etc, the ability to generate Java bytecode and take advantage of the JDK classes and JIT compiler has obvious benefits.
Answering just your second question:
The JVM is just an abstract machine and execution model. So targetting it with a compiler is just the same as any other machine and execution model that a compiler might target, be it implemented in hardware (x86, CELL, etc) or software (parrot, .NET). The JVM is fairly simple, so its actually a fairly easy target for compilers. Also, implementations tend to have pretty good JIT compilers (to deal with the lousy code that javac produces), so you can get good performance without having to worry about a lot of optimizations.
A couple of caveats apply. First, the JVM directly embodies java's module and inheritance system, so trying to do anything else (multiple inheritance, multiple dispatch) is likely to be tricky and require convoluted code. Second, JVMs are optimized to deal with the kind of bytecode that javac produces. Producing bytecode that is very different from this is likely to get into odd corners of the JIT compiler/JVM which will likely be inefficient at best (at worst, they can crash the JVM or at least give spurious VirtualMachineError exceptions).
What the JVM can do is defined by the JVM's bytecode (what you find in .class files) rather than the source language. So changing the high level source code language isn't going to have a substantial impact on the available functionality.
As for what is required to write a compiler for the JVM, all you really need to do is generate correct bytecode / .class files. How you write/compile code with an alternate compiler sort of depends on the compiler in question, but once the compiler outputs .class files, running them is no different than running the .class files generated by javac.
The advantage for these other languages is that they get relatively easy access to lots of java libraries.
The advantage for Java people varies depending on language -- each has a story tell Java coders about what they do better. Some will stress how they can be used to add dynamic scripting to JVM-based apps, others will just talk about how their language is easier to use, has a better syntax, or so forth.
What's required are the same things to write any other language compiler: parsing to an AST, then transforming that to instructions for the target architecture (byte code) and storing it in the right format (.class files).
From the users' perspective, you just write code and run the compiler binaries, and out comes .class files you can mix in with those your java compiler produces.
The .NET languages are more for show than actual usefulness. Each language has been so butchered, that they're all C# with a new face.
There are a variety of reasons to provide alternative languages for the Java VM:
The JVM is multiplatform. Any language ported to the JVM gets that as a free bonus.
There is quite a bit of legacy code out there. Antiquated engines like ColdFusion perform better while offering customers the ability to slowly phase their applications from the legacy solution to the modern solution.
Certain forms of scripting are better suited to rapid development. JavaFX, for example, is designed with rapid Graphical development in mind. In this way it competes with engines like DarkBasic. (Processing is another player in this space.)
Scripting environments can offer control. For example, an application may wish to expose a VBA-like environment to the user without exposing the underlying Java APIs. Using an engine like Rhino can provide an environment that supports quick and dirty coding in a carefully controlled sandbox.
Interpreted scripts mean that there's no need to recompile anything. No need to recompile translates into a more dynamic environment. e.g. Despite OpenOffice's use of Java as a "scripting language", Java sucks for that use. The user has to go through all kinds of recompile/reload gyrations that are unnecessary in a dynamic scripting environment like Javascript.
Which brings me to another point. Scripting engines can be more easily stopped and reloaded without stopping and reloading the entire JVM. This increases the utility of the scripting language as the environment can be reset at any time.
It's much easier for a compiler writer to generate JVM or CLR byte-codes. They are a much cleaner and higher level abstraction than any machine language. Because of this, it is much more feasible to experiment with creating new languages than ever before, because all you have to do is target one of these VM architectures and you will have a set of tools and libraries already available for your language. They let language designers focus more on the language than all the necessary support infrastructure.
Because the JSR process is rendering Java more and more dead: http://www.infoq.com/news/2009/01/java7-updated
It's a shame that even essential and long known additions like Closures are not added just because the members cannot agree on an implementation.
Java has accumulated a massive user base over seven major versions (from 1.0 to 1.6). Its capability to evolve is limited by the need to preserve backwards compatibility for the uncountable millions of lines of Java code running in production.
This is a problem because Java needs to evolve to:
compete with newer programming languages that have learned from Java's successes and failures.
incorporate new advances in programming language design.
allow users to take full advantage of advances in hardware - e.g. multi-core processors.
fix some cutting edge ideas that introduced unexpected problems (e.g. checked exceptions, generics).
The requirement for backwards compatibility is a barrier to staying competitive.
If you compare Java to C#, Java has the advantage in mature, production ready libraries and frameworks, and a disadvantage in terms of language features and rate of increase in market share. This is what you would expect from comparing two successful languages that are one generation apart.
Any new language has the same advantage and disadvantage that C# has compared to Java to an extreme degree. One way of maximizing the advantage in terms of language features, and minimizing the disadvantage in terms of mature libraries and frameworks is to build the language for an existing virtual machine and make it interoperable with code written for that virtual machine. This is the reason behind the modest success of Groovy and Clojure; and the excitement around Scala. Without the JVM these languages could only ever have occupied a tiny niche in a very specialized market segment, whereas with the JVM they occupy a significant niche in the mainstream.
They do it to keep up with .Net. .Net allows C#, VB, J# (formerly), F#, Python, Ruby (coming soon), and c++. I'm probably missing some. Probably the big one in there is Python, for the scripting people.
To an extent it is probably an 'Arms Race' against the .NET CLR.
But I think there are also genuine reasons for introducing new languages to the JVM, particularly when they will be run 'in parallel', you can use the right language for the right job, a scripting language like Groovy may be exactly what you need for your page presentation, whereas regular old Java is better for your business logic.
I'm going to leave someone more qualified to talk about what is required to write a new language/compiler.
As for how to writing code, you do it in notepad/vi as usual! (or use a development tool that supports the language if you want to do it the easy way.) Compiling will require a special compiler for the language that will interpret and compile it into bytecode.
Since java also produces bytecode technically you don't need to do anything special to run it.
The reason is that the JVM platform offers a lot of advantages.
Giant number of libraries
Broader degree of platform
implementations
Mature frameworks
Legacy code that's
already part of your infrastructure
The languages Sun is trying to support with their Scripting spec (e.g. Python, Ruby) are up and comers largely due to their perceived productivity enhancements. Running Jython allows you to, in theory, be more productive, and leverage the capabilities of Python to solve a problem more suited to Python, but still be able to integrate, on a runtime level, with your existing codebase. The classic implementations of Python and Ruby effect the same ability for C libraries.
Additionally, it's often easier to express some things in a dynamic language than in Java. If this is the case, you can go the other way; consume Python/Ruby libraries from Java.
There's a performance hit, but many are willing to accept that in exchange for a less verbose, clearer codebase.
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Bootstrapping a language
What's the importance of having an interpreter for a given language written in the target language (for example, PyPy)?
It's not so much about writing the interpreter in itself - more about writing the interpreter in a high-level language, not in C. Ideally, doing so allows to change details of the implementation, and making the interpreter more modular.
For the specific case of PyPy, writing the interpreter and the core objects in (R)Python allows to retarget PyPy for targets (C, JVM, .NET, JavaScript, etc), and also allows to replace aspects such as the garbage collector.
I'm sure there are many different reasons for doing it. In some cases, it's because you truly believe the language is the best tool... so writing the language interpreter or compiler in the language itself can be seen as a form of dogfooding. If you are really interested in this subject, the following article is a really amazing read about the development of squeak. The current version of squeak is a smalltalk runtime written in smalltalk.
http://users.ipa.net/~dwighth/squeak/oopsla_squeak.html
An added benefit is that if you implement good debugers and IDEs for your target language, they also work for your source language.
This way, you can prove that the target language is serious business, because being able to make it compile something is a sign that it is a good language.
OK, C++ and Java produce compilers as well... so maybe that argument is only half as good as it may seem.