Function parse_expression 

pub fn parse_expression(expr: &str) -> Result<ExprAST<'_>>

Usage

You can easily parse a string into ExprAST via this method.

use expression_engine::parse_expression;
let input = "a + 3*2+test()+[1,2,3,'haha']";
let ast = parse_expression(input);
assert!(ast.is_ok());