Rhai is an embedded scripting language and evaluation engine for Rust that gives a safe and easy way to add scripting to any application.
- All CPU and O/S targets supported by Rust, including:
- WebAssembly (WASM)
no-std
- Minimum Rust version 1.60.0
- Simple language similar to JavaScript+Rust with dynamic typing.
- Fairly efficient evaluation (1 million iterations in 0.3 sec on a single-core, 2.3 GHz Linux VM).
- Tight integration with native Rust functions and types, including getters/setters, methods and indexers.
- Freely pass Rust values into a script as variables/constants via an external
Scope- all clonable Rust types are supported; no need to implement any special trait. Or tap directly into the variable resolution process. - Built-in support for most common data types including booleans, integers, floating-point numbers (including
Decimal), strings, Unicode characters, arrays (including packed byte arrays) and object maps. - Easily call a script-defined function from Rust.
- Relatively little
unsafecode (yes there are some for performance reasons). - Few dependencies - currently only
smallvec,num-traits,ahash,bitflagsandsmartstring. - Re-entrant scripting engine can be made
Send + Sync(via thesyncfeature). - Compile once to AST form for repeated evaluations.
- Scripts are optimized (useful for template-based machine-generated scripts).
- Easy custom API development via plugins system powered by procedural macros.
- Function overloading and operator overloading.
- Dynamic dispatch via function pointers with additional support for currying.
- Closures (anonymous functions) that can capture shared values.
- Some syntactic support for object-oriented programming (OOP).
- Organize code base with dynamically-loadable modules, optionally overriding the resolution process.
- Serialization/deserialization support via serde (requires the
serdefeature). - Support for minimal builds by excluding unneeded language features.
- A debugging interface.
- 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.
- Sand-boxed - the scripting engine, if declared immutable, cannot mutate the containing environment unless explicitly permitted.
- Rugged - protected against malicious attacks (such as stack-overflow, over-sized data, and runaway scripts etc.) that may come from untrusted third-party user-land scripts.
- Track script evaluation progress and manually terminate a script run.
- Passes Miri.
- Use as a DSL.
- Disable certain language features such as looping.
- Further restrict the language by surgically disabling keywords and operators.
- Define custom operators.
- Extend the language with custom syntax.
The scripts subdirectory contains sample Rhai scripts.
Below is the standard Fibonacci example for scripting languages:
// This Rhai script calculates the n-th Fibonacci number using a
// really dumb algorithm to test the speed of the scripting engine.
const TARGET = 28;
const REPEAT = 5;
const ANSWER = 317_811;
fn fib(n) {
if n < 2 {
n
} else {
fib(n-1) + fib(n-2)
}
}
print(`Running Fibonacci(${TARGET}) x ${REPEAT} times...`);
print("Ready... Go!");
let result;
let now = timestamp();
for n in 0..REPEAT {
result = fib(TARGET);
}
print(`Finished. Run time = ${now.elapsed} seconds.`);
print(`Fibonacci number #${TARGET} = ${result}`);
if result != ANSWER {
print(`The answer is WRONG! Should be ${ANSWER}!`);
}See The Rhai Book for details on the Rhai scripting engine and language.
An Online Playground is available with syntax-highlighting editor, powered by WebAssembly.
Scripts can be evaluated directly from the editor.
Licensed under either of the following, at your choice:
Unless explicitly stated otherwise, any contribution intentionally submitted for inclusion in this crate, as defined in the Apache-2.0 license, shall be dual-licensed as above, without any additional terms or conditions.