exprkit

A mathematical expression parser and evaluator library for Rust, inspired by the ExprTk C++ library.

Features

• Parse and evaluate mathematical expressions at runtime
• Variables, constants, and arrays
• User-defined functions
• Control flow (if/else, loops, switch)
• 100+ built-in mathematical functions
• String operations
• Vector/array operations with BLAS-like functions

Quick Start

Add to your Cargo.toml:

[dependencies]
exprkit = "0.1"

Basic Usage

use exprkit::{Expression, SymbolTable};

fn main() {
    let mut symbol_table = SymbolTable::<f64>::new();
    symbol_table.add_variable("x", 2.0);
    symbol_table.add_variable("y", 3.0);

    let mut expr = Expression::new();
    expr.compile_with_symbol_table("x + y * 2", symbol_table).unwrap();

    let result = expr.value();
    assert_eq!(result, 8.0); // 2 + 3 * 2 = 8
}

Variables and Arrays

use exprkit::{Expression, SymbolTable};

let mut symbol_table = SymbolTable::<f64>::new();
symbol_table.add_variable("x", 1.0);
symbol_table.add_vector("v", vec![1.0, 2.0, 3.0, 4.0, 5.0]);

let mut expr = Expression::new();
expr.compile_with_symbol_table("sum(v) + x", symbol_table).unwrap();

assert_eq!(expr.value(), 16.0); // 15 + 1 = 16

Control Flow

use exprkit::{Expression, SymbolTable};

let mut symbol_table = SymbolTable::<f64>::new();
symbol_table.add_variable("x", 10.0);

let mut expr = Expression::new();
expr.compile_with_symbol_table(
    "if (x > 5) { x * 2 } else { x / 2 }",
    symbol_table
).unwrap();

assert_eq!(expr.value(), 20.0);

User-Defined Functions

use exprkit::{Expression, SymbolTable};

let mut symbol_table = SymbolTable::<f64>::new();
symbol_table.add_function("double", Box::new(|args: &[f64]| args[0] * 2.0));
symbol_table.add_variable("x", 5.0);

let mut expr = Expression::new();
expr.compile_with_symbol_table("double(x) + 1", symbol_table).unwrap();

assert_eq!(expr.value(), 11.0);

Built-in Functions

Mathematical Functions

sin, cos, tan, asin, acos, atan, sinh, cosh, tanh, exp, log, log10, log2, sqrt, abs, ceil, floor, round, trunc, erf, erfc, pow, mod, min, max, clamp, hypot, atan2

Aggregation Functions

sum, avg, mul, min, max

Vector Functions

sum, avg, min, max, dot, axpy, axpby, axpyz, nrm2

Combinatorics

fib (Fibonacci), ncr (combinations), npr (permutations)

Statistical

erf, erfc, ncdf (normal CDF)

CLI Tool

The exprkit binary provides a command-line expression evaluator. Install with the cli feature:

cargo install exprkit --features cli

Usage:

$ exprkit "2 + 2"
4

$ exprkit "sin(pi/2)"
1

$ exprkit --var x=5 "x * 2"
10

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Acknowledgments

This library is inspired by ExprTk by Arash Partow.