Crate eval [−] [src]

Eval is a powerful expression evaluator.

Supported operators: ! != "" '' () [] , > < >= <= == + - * / % && || n..m.

Built-in functions: min() max() len() is_empty().

Examples

You can do mathematical calculations with supported operators:

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:

use eval::{Expr, to_value};

assert_eq!(Expr::new("foo == bar")
               .value("foo", true)
               .value("bar", true)
               .exec(),
           Ok(to_value(true)));

You can eval with function:

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 []:

use eval::{eval, to_value};

assert_eq!(eval("[1, 2, 3, 4, 5]"), Ok(to_value(vec![1, 2, 3, 4, 5])));

You can create an integer array with n..m:

use eval::{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 the a boolean. Check whether the value is empty or not.

Structs

ExecOptions	Execute options
Expr	Expression builder
Function	Custom function

Enums

Error	Expression parsing error
Value	Represents a JSON value

Functions

eval	Evaluates the value of an expression.
to_value	Shortcut function to encode a `T` into a JSON `Value`

Type Definitions

Context	Custom context.
Contexts	Custom contexts. The value of the last context is searched first.
Functions	Custom functions.