Expand description
Eval is a powerful expression evaluator.
Supported operators: !
!=
""
''
()
[]
.
,
>
<
>=
<=
==
+
-
*
/
%
&&
||
n..m
.
Built-in functions: min()
max()
len()
is_empty()
array()
.
Examples
You can do mathematical calculations with supported operators:
use resolver::{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:
use resolver::{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.
use resolver::{Expr, to_value};
use std::collections::HashMap;
let mut object = HashMap::new();
object.insert("foos", vec!["Hello", "world", "!"]);
assert_eq!(Expr::new("object.foos[2-1] == 'world'") // Access field `foos` and index `2-1`
.value("object", object)
.exec(),
Ok(to_value(true)));
You can eval with function:
use resolver::{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()
:
use resolver::{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
:
use resolver::{eval, to_value};
assert_eq!(eval("0..5"), Ok(to_value(vec![0, 1, 2, 3, 4])));
Built-in functions
min()
Accept multiple arguments and return the minimum value.
max()
Accept multiple arguments and return the maximum value.
len()
Accept single arguments and return the length of value. Only accept String, Array, Object and Null.
is_empty()
Accept single arguments and return a boolean. Check whether the value is empty or not.
array()
Accept multiple arguments and return an array.
Structs
- Execute options
- Expression builder
- Custom function
Enums
- Expression parsing error
- Represents any valid JSON value.
Functions
- Evaluates the value of an expression.
- Convert variable to
serde_json::Value
Type Definitions
- Custom static function. Like fn
- Custom context.
- Custom contexts. The value of the last context is searched first.
- Custom functions.