108 lines
2.1 KiB
Markdown
108 lines
2.1 KiB
Markdown
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eval
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====
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[](https://docs.rs/eval)
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Eval is a powerful expression evaluator.
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## [Document](https://docs.rs/eval)
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## Features
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Supported operators: `!` `!=` `""` `''` `()` `[]` `,` `>` `<` `>=` `<=` `==`
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`+` `-` `*` `/` `%` `&&` `||` `n..m`.
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Built-in functions: `min()` `max()` `len()` `is_empty()`.
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## Where can eval be used?
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* Template engine
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* ...
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## Usage
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Add dependency to Cargo.toml
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```toml
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[dependencies]
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eval = "^0.3"
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```
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In your `main.rs` or `lib.rs`:
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```rust
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extern crate eval;
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```
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## Examples
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You can do mathematical calculations with supported operators:
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```
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use eval::{eval, to_value};
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assert_eq!(eval("1 + 2 + 3"), Ok(to_value(6)));
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assert_eq!(eval("2 * 2 + 3"), Ok(to_value(7)));
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assert_eq!(eval("2 / 2 + 3"), Ok(to_value(4.0)));
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assert_eq!(eval("2 / 2 + 3 / 3"), Ok(to_value(2.0)));
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```
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You can eval with context:
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```
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use eval::{Expr, to_value};
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assert_eq!(Expr::new("foo == bar")
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.value("foo", true)
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.value("bar", true)
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.exec(),
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Ok(to_value(true)));
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```
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You can access data like javascript by using `.` and `[]`. `[]` supports expression.
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```
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use eval::{Expr, to_value};
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use std::collections::HashMap;
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let mut object = HashMap::new();
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object.insert("foos", vec!["Hello", "world", "!"]);
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assert_eq!(Expr::new("object.foos[1-1] == 'Hello'")
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.value("object", object)
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.exec(),
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Ok(to_value(true)));
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```
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You can eval with function:
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```
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use eval::{Expr, to_value};
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assert_eq!(Expr::new("say_hello()")
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.function("say_hello", |_| Ok(to_value("Hello world!")))
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.exec(),
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Ok(to_value("Hello world!")));
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```
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You can create an array with `[]`:
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```
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use eval::{eval, to_value};
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assert_eq!(eval("[1, 2, 3, 4, 5]"), Ok(to_value(vec![1, 2, 3, 4, 5])));
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```
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You can create an integer array with `n..m`:
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```
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use eval::{eval, to_value};
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assert_eq!(eval("0..5"), Ok(to_value(vec![0, 1, 2, 3, 4])));
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```
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## License
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eval is primarily distributed under the terms of the MIT license.
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See [LICENSE](LICENSE) for details.
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