What algorithm does Excel use to recalculate formulas?

Question

Are the formulas represented in a syntax tree then recalculated using a design pattern like the Visitor pattern? How would you go about reproducing the recalculation process

Answer 1

Resolver One was a spreadsheet developed using IronPython.

Its source code has been released as Dirigible Spreadsheet. There used to be an article that described its overall algorithm: