Crate eval

Expression evaluator.

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

Built-in functions: min() max() 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::{eval_with_context, Context, to_value};

let mut context = Context::new();
context.insert("foo".to_owned(), to_value(true));
context.insert("bar".to_owned(), to_value(true));
assert_eq!(eval_with_context("foo == bar", &context), Ok(to_value(true)));

You can eval with functions:

use eval::{eval_with_functions, Functions, Function, to_value};

let mut functions = Functions::new();
functions.insert("say_hello".to_owned(), Function::new(|_| Ok(to_value("Hello world!"))));
assert_eq!(eval_with_functions("say_hello()", &functions), 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])));

Structs

Function

Custom function

Enums

Error	Expression parsing error
Value	Represents a JSON value

Functions

eval	Evaluates the value of an expression.
eval_with_context	Evaluates the value of an expression with the given context.
eval_with_context_and_functions	Evaluates the value of an expression with the given context and functions.
eval_with_contexts	Evaluates the value of an expression with the given contexts. The value of the last context is searched first.
eval_with_contexts_and_functions	Evaluates the value of an expression with the given contexts and functions. The value of the last context is searched first.
eval_with_functions	Evaluates the value of an expression with the given functions.
to_value	Shortcut function to encode a T into a JSON Value

Type Definitions

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