Eval is a library for boolean expression evaluation
let expr = Parser::parse("(a IN ('one', 'two') AND b => 13) OR c IS NOT NULL").unwrap();
let mut ctx = Context::new();
ctx.insert(String::from("a"), Value::Str("one".to_string()));
ctx.insert(String::from("b"), Value::Int(2));
ctx.insert(String::from("c"), Value::Bool(true));
assert!(expr.eval(&ctx));