Crate bel 

Better Expression Language (BEL), a non-Turing complete expression language designed for simplicity, speed, and safety.

BEL is ideal for lightweight expression evaluation when a scripting language or a WASM module would be too resource intensive.

jwt.exp < now().unix()
path.starts_with("/api") || path.matches(Regex("^/(admin|secret)"))
headers.all(header, header.length() < 256)

Types

String, Int, Float, Regex, Timestamp, Duration.

Example

Create and execute a simple BEL expression:

use bel::{Context, Program, Value};

let program = Program::compile("add(40, 2) == 42").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, Value::Bool(true));

Re-exports

pub use common::ast::IdedExpr;

pub use context::Context;

pub use functions::FunctionContext;

pub use objects::ResolveResult;

pub use objects::Value;

pub use parser::ParseError;

pub use parser::ParseErrors;

Modules

common

context

duration

A signed duration type for the expression language.

extractors

functions

objects

parser

Macros

impl_conversions

impl_handler

Structs

Duration

A wrapper Duration type which allows conversion to Value::Duration for types using automatic conversion with serde::Serialize.

Ip

Program

Timestamp

A wrapper Timestamp type which allows conversion to Value::Timestamp for types using automatic conversion with serde::Serialize.

Enums

ConvertToJsonError

ExecutionError

SerializationError

Functions

to_value