Yukihiro "Matz" Matsumoto
dccd66f9ef
The Difference Since Ruby1.9, the keyword arguments were emulated by Ruby using the hash object at the bottom of the arguments. But we have gradually moved toward keyword arguments separated from normal (positinal) arguments. At the same time, we value compatibility, so that Ruby3.0 keyword arguments are somewhat compromise. Basically, keyword arguments are separated from positional arguments, except when the method does not take any formal keyword arguments, given keyword arguments (packed in the hash object) are considered as the last argument. And we also allow non symbol keys in the keyword arguments. In that case, those keys are just passed in the `**` hash (or raise `ArgumentError` for unknown keys). The Instruction Changes We have changed `OP_SEND` instruction. `OP_SEND` instruction used to take 3 operands, the register, the symbol, the number of (positional) arguments. The meaning of the third operand has been changed. It is now considered as `n|(nk<<4)`, where `n` is the number of positional arguments, and `nk` is the number of keyword arguments, both occupies 4 bits in the operand. The number `15` in both `n` and `nk` means variable sized arguments are packed in the object. Positional arguments will be packed in the array, and keyword arguments will be packed in the hash object. That means arguments more than 14 values are always packed in the object. Arguments information for other instructions (`OP_SENDB` and `OP_SUPER`) are also changed. It works as the third operand of `OP_SEND`. the difference between `OP_SEND` and `OP_SENDB` is just trivial. It assigns `nil` to the block hidden arguments (right after arguments). The instruction `OP_SENDV` and `OP_SENDVB` are removed. Those instructions are replaced by `OP_SEND` and `OP_SENDB` respectively with the `15` (variable sized) argument information. Calling Convention When calling a method, the stack elements shall be in the order of the receiver of the method, positional arguments, keyword arguments and the block argument. If the number of positional or keyword arugument (`n` or `nk`) is zero, corresponding arguments will be empty. So when `n=0` and `nk=0` the stack layout (from bottom to top) will be: +-----------------------+ | recv | block (or nil) | +-----------------------+ The last elements `block` should be explicitly filled before `OP_SEND` or assigned to `nil` by `OP_SENDB` internally. In other words, the following have exactly same behavior: OP_SENDB clears `block` implicitly: ``` OP_SENDB reg sym 0 ``` OP_SEND clears `block` implicitly: ``` OP_LOADNIL R2 OP_SEND R2 sym 0 ``` When calling a method with only positional arguments (n=0..14) without keyword arguments, the stack layout will be like following: +--------------------------------------------+ | recv | arg1 | ... | arg_n | block (or nil) | +--------------------------------------------+ When calling a method with arguments packed in the array (n=15) which means argument splat (*) is used in the actual arguments, or more than 14 arguments are passed the stack layout will be like following: +-------------------------------+ | recv | array | block (or nil) | +-------------------------------+ The number of the actual arguments is determined by the length of the argument array. When keyword arguments are given (nk>0), keyword arguments are passed between positional arguments and the block argument. For example, when we pass one positional argument `1` and one keyword argument `a: 2`, the stack layout will be like: +------------------------------------+ | recv | 1 | :a | 2 | block (or nil) | +------------------------------------+ Note that keyword arguments consume `2*nk` elements in the stack when `nk=0..14` (unpacked). When calling a method with keyword arguments packed in the hash object (nk=15) which means keyword argument splat (**) is used or more than 14 keyword arguments in the actual arguments, the stack layout will be like: +------------------------------+ | recv | hash | block (or nil) | +------------------------------+ Note for mruby/c When mruby/c authors try to support new keyword arguments, they need to handle the new meaning of the argument information operand. If they choose not to support keyword arguments in mruby/c, it just raise error when `nk` (taken by `(c>>4)&0xf`) is not zero. And combine `OP_SENDV` behavior with `OP_SEND` when `n` is `15`. If they want to support keyword arguments seriously, contact me at <matz@ruby.or.jp> or `@yukihiro_matz`. I can help you.
mruby
What is mruby
mruby is the lightweight implementation of the Ruby language complying to (part of) the ISO standard. Its syntax is Ruby 2.x compatible.
mruby can be linked and embedded within your application. We provide the interpreter program "mruby", and the interactive mruby shell "mirb" as examples. You can also compile Ruby programs into compiled byte code using the mruby compiler "mrbc". All those tools reside in the "bin" directory. "mrbc" is also able to generate compiled byte code in a C source file, see the "mrbtest" program under the "test" directory for an example.
This achievement was sponsored by the Regional Innovation Creation R&D Programs of the Ministry of Economy, Trade and Industry of Japan.
How to get mruby
The stable version 3.0.0 of mruby can be downloaded via the following URL: https://github.com/mruby/mruby/archive/3.0.0.zip
The latest development version of mruby can be downloaded via the following URL: https://github.com/mruby/mruby/zipball/master
The trunk of the mruby source tree can be checked out with the following command:
$ git clone https://github.com/mruby/mruby.git
You can also install and compile mruby using ruby-install, ruby-build or rvm.
mruby home-page
The URL of the mruby home-page is: https://mruby.org.
Mailing list
We don't have a mailing list, but you can use GitHub issues.
How to compile, test, and install (mruby and gems)
See the compile.md file.
Building documentation
There are two sets of documentation in mruby: the mruby API (generated by yard) and C API (Doxygen)
To build both of them, simply go
rake doc
You can also view them in your browser
rake view_api
rake view_capi
How to customize mruby (mrbgems)
mruby contains a package manager called mrbgems. To create extensions in C and/or Ruby you should create a GEM. For a documentation of how to use mrbgems consult the file mrbgems.md. For example code of how to use mrbgems look into the folder examples/mrbgems/.
License
mruby is released under the MIT License.
Note for License
mruby has chosen a MIT License due to its permissive license allowing developers to target various environments such as embedded systems. However, the license requires the display of the copyright notice and license information in manuals for instance. Doing so for big projects can be complicated or troublesome. This is why mruby has decided to display "mruby developers" as the copyright name to make it simple conventionally. In the future, mruby might ask you to distribute your new code (that you will commit,) under the MIT License as a member of "mruby developers" but contributors will keep their copyright. (We did not intend for contributors to transfer or waive their copyrights, Actual copyright holder name (contributors) will be listed in the AUTHORS file.)
Please ask us if you want to distribute your code under another license.
How to Contribute
See the contribution guidelines, and then send a pull request to https://github.com/mruby/mruby. We consider you have granted non-exclusive right to your contributed code under MIT license.