115 lines
2.4 KiB
Markdown
115 lines
2.4 KiB
Markdown
eval
|
|
====
|
|
|
|
[](http://www.repostatus.org/#active)
|
|
[](https://docs.rs/eval)
|
|
|
|
Eval is a powerful expression evaluator.
|
|
|
|
[Document](https://docs.rs/eval)
|
|
--------------------------------
|
|
|
|
Features
|
|
--------
|
|
|
|
Supported operators: `!` `!=` `""` `''` `()` `[]` `,` `>` `<` `>=` `<=` `==`
|
|
`+` `-` `*` `/` `%` `&&` `||` `n..m`.
|
|
|
|
Built-in functions: `min()` `max()` `len()` `is_empty()` `array()`.
|
|
|
|
Where can eval be used?
|
|
-----------------------
|
|
|
|
* Template engine
|
|
* ...
|
|
|
|
Usage
|
|
-----
|
|
|
|
Add dependency to Cargo.toml
|
|
|
|
```toml
|
|
[dependencies]
|
|
eval = "^0.4"
|
|
```
|
|
|
|
In your `main.rs` or `lib.rs`:
|
|
|
|
```rust
|
|
extern crate eval;
|
|
```
|
|
|
|
Examples
|
|
--------
|
|
|
|
You can do mathematical calculations with supported operators:
|
|
|
|
```rust
|
|
use eval::{eval, to_value};
|
|
|
|
assert_eq!(eval("1 + 2 + 3"), Ok(to_value(6)));
|
|
assert_eq!(eval("2 * 2 + 3"), Ok(to_value(7)));
|
|
assert_eq!(eval("2 / 2 + 3"), Ok(to_value(4.0)));
|
|
assert_eq!(eval("2 / 2 + 3 / 3"), Ok(to_value(2.0)));
|
|
```
|
|
|
|
You can eval with context:
|
|
|
|
```rust
|
|
use eval::{Expr, to_value};
|
|
|
|
assert_eq!(Expr::new("foo == bar")
|
|
.value("foo", true)
|
|
.value("bar", true)
|
|
.exec(),
|
|
Ok(to_value(true)));
|
|
```
|
|
|
|
You can access data like javascript by using `.` and `[]`. `[]` supports expression.
|
|
|
|
```rust
|
|
use eval::{Expr, to_value};
|
|
use std::collections::HashMap;
|
|
|
|
let mut object = HashMap::new();
|
|
object.insert("foos", vec!["Hello", "world", "!"]);
|
|
|
|
assert_eq!(Expr::new("object.foos[1-1] == 'Hello'")
|
|
.value("object", object)
|
|
.exec(),
|
|
Ok(to_value(true)));
|
|
```
|
|
|
|
You can eval with function:
|
|
|
|
```rust
|
|
use eval::{Expr, to_value};
|
|
|
|
assert_eq!(Expr::new("say_hello()")
|
|
.function("say_hello", |_| Ok(to_value("Hello world!")))
|
|
.exec(),
|
|
Ok(to_value("Hello world!")));
|
|
```
|
|
|
|
You can create an array with `array()`:
|
|
|
|
```rust
|
|
use eval::{eval, to_value};
|
|
|
|
assert_eq!(eval("array(1, 2, 3, 4, 5)"), Ok(to_value(vec![1, 2, 3, 4, 5])));
|
|
```
|
|
|
|
You can create an integer array with `n..m`:
|
|
|
|
```rust
|
|
use eval::{eval, to_value};
|
|
|
|
assert_eq!(eval("0..5"), Ok(to_value(vec![0, 1, 2, 3, 4])));
|
|
```
|
|
|
|
License
|
|
-------
|
|
|
|
eval is primarily distributed under the terms of the MIT license.
|
|
See [LICENSE](LICENSE) for details.
|