Crate zen_expression

A lightweight expression language designed for the evaluation of expressions in various contexts.

Zen Expression is a versatile single-threaded expression language designed for simplicity high-performance. It’s primarily used for evaluating and processing JSON data offers key components that empower developers in creating responsive and non-blocking I/O applications Out of the box, it comes with amazing benefits:

• 🚀 Blazingly fast - Perform millions of evaluations per second
• 🧠 Intuitive syntax - Minimalistic and expressive syntax
• 💼 Portable - Can be compiled for all standard architectures including WASM

For a full list of language references, visit documentation.

Example

Evaluate expression using isolate:

use zen_expression::evaluate_expression;
use zen_expression::variable::Variable;
use rust_decimal_macros::dec;
use serde_json::json;

fn main() {
    let context = json!({ "tax": { "percentage": 10 } });
    let tax_amount = evaluate_expression("50 * tax.percentage / 100", context.into()).unwrap();

    assert_eq!(tax_amount, Variable::Number(dec!(5)));
}

High Performance

When evaluating a lot of expressions at once, you can use Isolate directly. Under the hood, Isolate will re-use allocated memory from previous evaluations, drastically improving performance.

use zen_expression::Isolate;
use zen_expression::variable::Variable;
use rust_decimal_macros::dec;
use serde_json::json;

fn main() {
    let context = json!({ "tax": { "percentage": 10 } });
    let mut isolate = Isolate::with_environment(context.into());

    // Fast 🚀
    for _ in 0..1_000 {
        let tax_amount = isolate.run_standard("50 * tax.percentage / 100").unwrap();
        assert_eq!(tax_amount, Variable::Number(dec!(5)));
    }
}

Feature flags

Name	Description	Default?
regex-deprecated	Uses standard regex crate	Yes
regex-lite	Opts for usage of lightweight regex-lite crate. Useful for reducing build size, especially in WASM.	No

Re-exports

• pub use variable::Variable;

Modules

• compiler
  Compilation from AST into Opcodes
• intellisense
• lexer
  Performs lexical analysis on string inputs
• parser
  Parses Tokens into AST
• variable
• vm
  Virtual Machine - Evaluation of Opcodes

Structs

• Isolate
  Isolate is a component that encapsulates an isolated environment for executing expressions.

Enums

• IsolateError
  Errors which happen within isolate or during evaluation

Functions

• evaluate_expression
  Evaluates a standard expression
• evaluate_unary_expression
  Evaluates a unary expression; Required: context must be an object with “$” key.