Document some cases where solution might not work well. Making class extendable and offering some over-rideable methods may allow for solutions to some of these problems.
Helper/TextGrid was intended to assist with some samples. However, it has emerged recently on two tickets. PR #4342 intended to introduce functionality very similar to TextGrid, and was closed for that reason. Issue #1640 was closed as stale over 4 years ago, despite the fact that TextGrid seems an adequate resolution for it.
Since it seems that there is a use for this function beyond its original intended usage, I added a few parameters to give it some flexibility - the ability to omit row and/or column headers, and the ability to add a divider line between rows.
A description of this function is added to the formal documentation.
Dealing mostly with mixed variable type. In a great many cases, problems can be resolved replacing `getValue` with `getValueString` or `getCalculatedValue` with `getCalculatedValueString`.
When I implemented IgnoredErrors (PR #3508), I dealt only with those that I understood well enough to come up with an example. I finally found an example for FormulaRange in the wild, so this PR adds it. Still unsupported are `calculatedColumn`, `emptyCellReferece`, `listDataValidation`, and `unlockedFormula`.
For an overview of why this is desired (and ways that people have coped with its absence), see issue #2900 and issue #4048; also PR #4043 which will be superseded by this PR.
The list of Excel functions is moved from Calculation/Calculation to its own member. I believe that it is done in a way that will not cause big complications to two experiments from @MarkBaker (PR #2714 and PR #2734). I believe it is also done in such a way that further refactoring of Calculation can follow this model.
Custom functions can be added or removed from the function list. You cannot add a function if it already exists in the list, and you cannot remove a non-custom function from the list. They will, of course, not be understood by Excel if written to a spreadsheet; the use case is mainly using the Calculation engine outside of spreadsheet context.