# Ripin-rs

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A library to handle [`Reverse Polish notated`](https://en.wikipedia.org/wiki/Reverse_Polish_notation) expressions.

Ripin can also evaluate variable expressions and is not limited to string tokens, it can handle any iterator type, the only limit is your imagination. There is [`examples`](https://github.com/Kerollmops/ripin-rs/tree/master/examples) to understand how to implement your own expression from custom types.

## Installation

Ripin is available on [crates.io](https://crates.io/crates/ripin) and can be included in your Cargo enabled project like this:

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

Then include it in your code like this:

```rust
extern crate ripin;
```

## Examples

Ripin can evaluate [`Reverse Polish Notated`](https://en.wikipedia.org/wiki/Reverse_Polish_notation) expressions.

```rust
use ripin::expression::FloatExpr;

let expr_str = "3 4 + 2 *"; // (3 + 4) * 2
let tokens = expr_str.split_whitespace();

let expr = FloatExpr::<f32>::from_iter(tokens).unwrap();

println!("Expression {:?} gives {:?}", expr_str, expr.evaluate())
```

It is also possible to use variables in your expressions to make them more "variable".

```rust
use std::collections::HashMap;
use ripin::evaluate::VariableFloatExpr;
use ripin::variable::IndexVar;

let mut variables = HashMap::new(); // using a Vec is the same
variables.insert(0, 3.0);
variables.insert(1, 500.0);

let expr_str = "3 $1 + 2 * $0 -"; // (3 + $1) * 2 - $0
let tokens = expr_str.split_whitespace();

let expr = VariableFloatExpr::<f32, IndexVar>::from_iter(tokens).unwrap();

let result = expr.evaluate_with_variables(&variables);

println!("Expression {:?} gives {:?}", expr_str, result); // Ok(1003)
```