Expand description
eval takes a &str and a &mut VecDeque<f64>, evaluates the expression,
and prints the result, pushing the results onto the stack of type
VecDeque
It does not return an error, but will instead silently fail if the expression is invalid. Additionally, it mutates the stack parameter, rather than returning a new one. Even if the stack is empty, it will still evaluate the expression. For this reason, eval is unsafe, and safe_eval or safe_eval_with_stack should be used.