The Common Expression Language (CEL) is a non-Turing complete language designed for simplicity, speed, safety, and portability. CEL's C-like syntax looks nearly identical to equivalent expressions in C++, Go, Java, and TypeScript. CEL is ideal for lightweight expression evaluation when a fully sandboxed scripting language is too resource intensive.
// Check whether a resource name starts with a group name. resource.name.startsWith("/groups/" + auth.claims.group)
// Determine whether the request is in the permitted time window. request.time - resource.age < duration("24h")
// Check whether all resource names in a list match a given filter. auth.claims.email_verified && resources.all(r, r.startsWith(auth.claims.email))
Add cel to your Cargo.toml:
[dependencies] cel = "0.12.0"
Create and execute a simple CEL expression:
use cel::{Context, Program}; fn main() { let program = Program::compile("add(2, 3) == 5").unwrap(); let mut context = Context::default(); context.add_function("add", |a: i64, b: i64| a + b); let value = program.execute(&context).unwrap(); assert_eq!(value, true.into()); }
Check out these other examples to learn how to use this library:
- Simple - A simple example of how to use the library.
- Variables - Passing variables and using them in your program.
- Functions - Defining and using custom functions in your program.
- Concurrent Execution - Executing the same program concurrently.