Support `eval_with_vars()`
It would be great if the library could support variables in the expression and evaluate them at runtime.
See the following example:
eval_with_vars("2 + {nn}", { xx = 3 }) // I know that this code won't work/compile.
Ideally, this would support a data structure which can hold arbitrary variable names (a Hashmap?) without limiting the type of the values. Maybe something like:
trait GetValue {
fn get_value(&self) -> Value;
}
fn eval_with_vars<T>(expression: &str, vars: &HashMap<&str, T>) -> Value
where T: GetValue
{
// stuff
}