150 lines
8.5 KiB
Markdown
150 lines
8.5 KiB
Markdown
Rhai - Embedded Scripting for Rust
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=================================
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[](https://github.com/rhaiscript/rhai/actions)
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[](https://github.com/rhaiscript/rhai)
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[](https://github.com/license/rhaiscript/rhai)
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[](https://crates.io/crates/rhai/)
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[](https://crates.io/crates/rhai/)
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[](https://docs.rs/rhai/)
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[](https://marketplace.visualstudio.com/items?itemName=rhaiscript.vscode-rhai)
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[](https://packagecontrol.io/packages/Rhai)
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[](https://discord.gg/HquqbYFcZ9)
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[](https://rhaiscript.zulipchat.com)
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[](https://www.reddit.com/r/Rhai)
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[](https://rhai.rs)
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Rhai is an embedded scripting language and evaluation engine for Rust that gives a safe and easy way
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to add scripting to any application.
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Targets and builds
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------------------
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* All CPU and O/S targets supported by Rust, including:
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* WebAssembly (WASM)
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* `no-std`
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* Minimum Rust version 1.57
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Standard features
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-----------------
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* Simple language similar to JavaScript+Rust with [dynamic](https://rhai.rs/book/language/dynamic.html) typing.
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* Fairly efficient evaluation (1 million iterations in 0.3 sec on a single-core, 2.3 GHz Linux VM).
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* Tight integration with native Rust [functions](https://rhai.rs/book/rust/functions.html) and [types]([#custom-types-and-methods](https://rhai.rs/book/rust/custom.html)), including [getters/setters](https://rhai.rs/book/rust/getters-setters.html), [methods](https://rhai.rs/book/rust/custom.html) and [indexers](https://rhai.rs/book/rust/indexers.html).
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* Freely pass Rust values into a script as [variables](https://rhai.rs/book/language/variables.html)/[constants](https://rhai.rs/book/language/constants.html) via an external [`Scope`](https://rhai.rs/book/rust/scope.html) - all clonable Rust types are supported; no need to implement any special trait. Or tap directly into the [variable resolution process](https://rhai.rs/book/engine/var.html).
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* Built-in support for most common [data types](https://rhai.rs/book/language/values-and-types.html) including booleans, [integers](https://rhai.rs/book/language/numbers.html), [floating-point numbers](https://rhai.rs/book/language/numbers.html) (including [`Decimal`](https://crates.io/crates/rust_decimal)), [strings](https://rhai.rs/book/language/strings-chars.html), [Unicode characters](https://rhai.rs/book/language/strings-chars.html), [arrays](https://rhai.rs/book/language/arrays.html) (including packed [byte arrays](https://rhai.rs/book/language/blobs.html)) and [object maps](https://rhai.rs/book/language/object-maps.html).
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* Easily [call a script-defined function](https://rhai.rs/book/engine/call-fn.html) from Rust.
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* Relatively little `unsafe` code (yes there are some for performance reasons).
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* Few dependencies - currently only [`smallvec`](https://crates.io/crates/smallvec), [`num-traits`](https://crates.io/crates/num-traits), [`ahash`](https://crates.io/crates/ahash) and [`smartstring`](https://crates.io/crates/smartstring).
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* Re-entrant scripting engine can be made `Send + Sync` (via the `sync` feature).
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* Compile once to [AST](https://rhai.rs/book/engine/compile.html) form for repeated evaluations.
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* Scripts are [optimized](https://rhai.rs/book/engine/optimize.html) (useful for template-based machine-generated scripts).
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* Easy custom API development via [plugins](https://rhai.rs/book/plugins) system powered by procedural macros.
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* [Function overloading](https://rhai.rs/book/language/overload.html) and [operator overloading](https://rhai.rs/book/rust/operators.html).
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* Dynamic dispatch via [function pointers](https://rhai.rs/book/language/fn-ptr.html) with additional support for [currying](https://rhai.rs/book/language/fn-curry.html).
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* [Closures](https://rhai.rs/book/language/fn-closure.html) (anonymous functions) that can capture shared values.
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* Some syntactic support for [object-oriented programming (OOP)](https://rhai.rs/book/language/oop.html).
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* Organize code base with dynamically-loadable [modules](https://rhai.rs/book/language/modules.html), optionally [overriding the resolution process](https://rhai.rs/book/rust/modules/resolvers.html).
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* Serialization/deserialization support via [serde](https://crates.io/crates/serde) (requires the `serde` feature).
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* Support for [minimal builds](https://rhai.rs/book/start/builds/minimal.html) by excluding unneeded language [features](https://rhai.rs/book/start/features.html).
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* A [debugging](https://rhai.rs/book/engine/debugging) interface.
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Protected against attacks
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-------------------------
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* _Don't Panic_ guarantee - Any panic is a bug. Rhai subscribes to the motto that a library should never panic the host system, and is coded with this in mind.
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* [Sand-boxed](https://rhai.rs/book/safety/sandbox.html) - the scripting engine, if declared immutable, cannot mutate the containing environment unless [explicitly permitted](https://rhai.rs/book/patterns/control.html).
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* Rugged - protected against malicious attacks (such as [stack-overflow](https://rhai.rs/book/safety/max-call-stack.html), [over-sized data](https://rhai.rs/book/safety/max-string-size.html), and [runaway scripts](https://rhai.rs/book/safety/max-operations.html) etc.) that may come from untrusted third-party user-land scripts.
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* Track script evaluation [progress](https://rhai.rs/book/safety/progress.html) and manually terminate a script run.
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For those who actually want their own language
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---------------------------------------------
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* Use as a [DSL](https://rhai.rs/book/engine/dsl.html).
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* Disable certain [language features](https://rhai.rs/book/engine/options.html#language-features) such as [looping](https://rhai.rs/book/engine/disable-looping.html).
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* Further restrict the language by surgically [disabling keywords and operators](https://rhai.rs/book/engine/disable-keywords.html).
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* Define [custom operators](https://rhai.rs/book/engine/custom-op.html).
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* Extend the language with [custom syntax](https://rhai.rs/book/engine/custom-syntax.html).
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Example
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-------
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The [`scripts`](https://github.com/rhaiscript/rhai/tree/master/scripts) subdirectory contains sample Rhai scripts.
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Below is the standard _Fibonacci_ example for scripting languages:
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```ts
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// This Rhai script calculates the n-th Fibonacci number using a
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// really dumb algorithm to test the speed of the scripting engine.
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const TARGET = 28;
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const REPEAT = 5;
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const ANSWER = 317_811;
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fn fib(n) {
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if n < 2 {
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n
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} else {
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fib(n-1) + fib(n-2)
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}
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}
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print(`Running Fibonacci(${TARGET}) x ${REPEAT} times...`);
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print("Ready... Go!");
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let result;
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let now = timestamp();
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for n in 0..REPEAT {
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result = fib(TARGET);
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}
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print(`Finished. Run time = ${now.elapsed} seconds.`);
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print(`Fibonacci number #${TARGET} = ${result}`);
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if result != ANSWER {
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print(`The answer is WRONG! Should be ${ANSWER}!`);
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}
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```
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Project Site
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------------
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[`rhai.rs`](https://rhai.rs)
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Documentation
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-------------
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See [_The Rhai Book_](https://rhai.rs/book) for details on the Rhai scripting engine and language.
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Playground
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----------
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An [_Online Playground_](https://rhai.rs/playground) is available with syntax-highlighting editor,
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powered by WebAssembly.
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Scripts can be evaluated directly from the editor.
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License
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-------
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Licensed under either of the following, at your choice:
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* [Apache License, Version 2.0](https://github.com/rhaiscript/rhai/blob/master/LICENSE-APACHE.txt), or
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* [MIT license](https://github.com/rhaiscript/rhai/blob/master/LICENSE-MIT.txt)
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Unless explicitly stated otherwise, any contribution intentionally submitted
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for inclusion in this crate, as defined in the Apache-2.0 license, shall
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be dual-licensed as above, without any additional terms or conditions.
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