Parsing algebraic expressions is always a pain ... The second parse returns a full expression to produce: (2+(4*2)). If that was too fast, read the post which has a nice flowchart and an example ...

A string of numbers and letters joined together by mathematical operations such as \(+\) and \(-\) is called an algebraic expression, for example \(r + 2s\). Suppose that \({g}\) is the cost of ...