160 lines
3.8 KiB
Markdown
160 lines
3.8 KiB
Markdown
# evalexpr
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[![docs](https://docs.rs/evalexpr/badge.svg?version=0.4.4 "docs")](https://docs.rs/evalexpr)
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Evalexpr is a powerful arithmetic and boolean expression evaluator.
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## [Documentation](https://docs.rs/evalexpr)
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<!-- cargo-sync-readme start -->
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## Features
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### Operators
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Supported binary operators:
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| Operator | Precedence | Description | | Operator | Precedence | Description |
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|----------|------------|-------------|---|----------|------------|-------------|
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| + | 95 | Sum | | < | 80 | Lower than |
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| - | 95 | Difference | | \> | 80 | Greater than |
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| * | 100 | Product | | <= | 80 | Lower than or equal |
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| / | 100 | Division | | \>= | 80 | Greater than or equal |
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| % | 100 | Modulo | | == | 80 | Equal |
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| && | 75 | Logical and | | != | 80 | Not equal |
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| || | 70 | Logical or | | | |
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Supported unary operators:
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| Operator | Precedence | Description |
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|----------|------------|-------------|
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| - | 110 | Negation |
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| ! | 110 | Logical not |
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### Values
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Operators take values as arguments and produce values as results.
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Values can be boolean, integer or floating point numbers.
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Strings are supported as well, but there are no operations defined for them yet.
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Integers are internally represented as `i64`, and floating point numbers are represented as `f64`.
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Operators that take numbers as arguments can either take integers or floating point numbers.
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If one of the arguments is a floating point number, all others are converted to floating point numbers as well, and the resulting value is a floating point number as well.
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Otherwise, the result is an integer.
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### Variables
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Supported binary operators: `!` `!=` `""` `''` `()` `[]` `,` `>` `<` `>=` `<=` `==`
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`+` unary/binary `-` `*` `/` `%` `&&` `||` `n..m`.
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Supported unary operators: ``
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Built-in functions: `min()` `max()` `len()` `is_empty()` `array()` `converge()`.
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See the `builtin` module for a detailed description of each.
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Where can eval be used?
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-----------------------
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* Template engine
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* Scripting language
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* ...
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Usage
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-----
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Add dependency to Cargo.toml
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```toml
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[dependencies]
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evalexpr = "0.4"
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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 evalexpr as eval;
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```
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Examples
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--------
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You can do mathematical calculations with supported operators:
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```rust
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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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```rust
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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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```rust
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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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```rust
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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 `array()`:
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```rust
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use eval::{eval, to_value};
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assert_eq!(eval("array(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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```rust
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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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-------
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evalexpr is primarily distributed under the terms of the MIT license.
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See [LICENSE](LICENSE) for details.
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<!-- cargo-sync-readme end -->
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