exprkit 0.1.0

# exprkit

[![Crates.io](https://img.shields.io/crates/v/exprkit.svg)](https://crates.io/crates/exprkit)
[![Documentation](https://docs.rs/exprkit/badge.svg)](https://docs.rs/exprkit)
[![License: MIT OR Apache-2.0](https://img.shields.io/badge/license-MIT%20OR%20Apache--2.0-blue.svg)](#license)

A mathematical expression parser and evaluator library for Rust, inspired by the [ExprTk C++ library](https://www.partow.net/programming/exprtk/).

## 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`:

```toml
[dependencies]
exprkit = "0.1"
```

### Basic Usage

```rust
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

```rust
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

```rust
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

```rust
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:

```bash
cargo install exprkit --features cli
```

Usage:

```bash
$ 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](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

## Acknowledgments

This library is inspired by [ExprTk](https://www.partow.net/programming/exprtk/) by Arash Partow.