108 lines
5.0 KiB
Markdown
108 lines
5.0 KiB
Markdown
# Libcubescript Documentation {#index}
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## What is Cubescript?
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ubescript is a minimal scripting language first introduced in the Cube FPS
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and carried over into derived games and game engines such as Sauerbraten.
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Originally being little more than a few hundred lines of code, serving
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primarily as the console and configuration file format of the game, it
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grew more advanced features as well as a bytecode VM.
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Nowadays, it is a minimal but relatively fully featured scripting language
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based around the concept that everything can be interpreted as a string.
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It excels at its original purpose as well as things like text preprocessing.
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It comes with a Lisp-like syntax and a variety of standard library functions.
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## What is Libcubescript?
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Libcubescript is a project that aims to provide an independent, improved,
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separate implementation of the language, available as a library, intended to
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satisfy the needs of the OctaForge project. It was originally forked from
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Cubescript as present in the Tesseract game/engine and gradually rewritten;
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right now, very little of the original code remains. At language level it is
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mostly compatible with the other implementations (although with a stricter
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parser and extra features), while the standard library does not aim to be
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fully compatible. Some features are also left up to the user to customize,
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so that it is not tied to game engines feature-wise.
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Like the codebase it is derived from, it is available under the permissive
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zlib license, and therefore compatible with just about anything.
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## Benefits and differences
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There's a variety of things that set this implementation apart:
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* It's independent and can be embedded in any project
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* There is no global state, so you can have as many Cubescripts as you want,
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in one program
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* Written in C++20, following modern language conventions, both internally
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and at API level
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* That means the ability to use lambdas as commands, including captures,
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type inference and so on
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* There is a robust allocator system in place, and all memory the library
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uses is allocated through it; that gives you complete control over its
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memory (for tracking, sandboxing, limits, etc.)
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* A large degree of memory safety, with no manual management
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* Strings are interned, with a single reference counted instance of any
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string existing at a time, which lowers memory usage and simplifies its
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management
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* Minimal stack memory usage, which means no artificial limits on recursion
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depth as well as safe usage from threads and coroutines with small stacks
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* Errors will no longer cause the interpreter to march on, instead acting
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like real errors
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* Protected calls allow you to catch errors in a similar way to exceptions,
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and nearly every error can be caught
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* Stricter parsing, with things like unfinished strings being caught
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* Loops now have `break` and `continue` statements
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* Customizable integer and floating point types
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* Full support for symbol visibility in API
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* Highly portable and cross-platform, no dependencies other than a compiler
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* Clean codebase that is easy to pick up and contribute to
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## Building and usage
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The library has absolutely no dependencies other than a C++20 compiler,
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similarly there are no dependencies on system or architecture specific
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things, so it should work on any OS and any CPU.
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The C++20 support does not have to be complete. These are the baselines
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(which are ensured by the CI):
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* GCC 10
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* Clang 10 (with libstdc++ or libc++)
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* Microsoft Visual C++ 2019
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Older versions of either of these are known not to work.
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You will need [Meson](https://mesonbuild.com/) to build the project. Most
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Unix-like systems have it in their package management, on Windows there is
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an installer available on their website. Being written in Python, you can
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also use `pip` to get an up to date version on any OS.
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Once you have it, compiling is simple, e.g. on Unix-likes you can do:
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~~~
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mkdir build && cd build
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meson ..
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ninja all
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~~~
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Refer to Meson's manual for how to customize whether you want a shared or
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static library and so on. By default, you will get a shared library plus
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a REPL (interactive interpreter). The REPL also serves as an example of
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how to use the API.
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If you don't want the REPL, use `-Drepl=disabled`. When compiled, it can
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have support for line editing and command history. This is provided through
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`linenoise` (which is a minimal single-file line editing library bundled
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with the project, and is the default). In case you're on a platform that
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`linenoise` does not support (highly unlikely), there is a fallback without
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any line editing as well. Pass `-Dlinenoise=disabled` to use the fallback.
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The version of `linenoise` bundled with the project is `cpp-linenoise`, available
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at https://github.com/yhirose/cpp-linenoise. Our version is modified, so that
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it builds cleanly with our flags, and so that it supports the "hints" feature
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available in original `linenoise`. Other than the modifications, it is baseed
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on upstream git revision `a927043cdd5bfe203560802e56a7e7ed43156ed3`. The reason
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we use this instead of upstream `linenoise` is Windows support.
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