* Extract ACCRINT() and ACCRINTM() Financial functions into their own class
Implement additional validations, with additional unit tests
Add support for the new calculation method argument for ACCRINT()
* Additional tests for Amortization functions
* Start work on breaking down some of the Financial Excel functions
* Unhappy path unit tests for Treasury Bill functions
* Codebase for Treasury Bills includes logic for a different days between settlement and maturity calculation for OpenOffice; but Open/Libre Office now uses the Excel days calculation, so this discrepancy between packages is no longer required
* We've already converted the Settlement and Maturity dates to Excel timestamps, so there's no need to try doing it again when calculating the days between Settlement and Maturity
* Add Unit Tests for the Days per Year helper function
* Extract Interest Rate functions - EFFECT() and NOMINAL() - with additional validation, and unhappy path unit tests
* First pass at extracting the Coupon Excel functions
* Simplify the validation methods
* Extended unit tests to cover all combinations of frequency and basis, including leap years
Fix for COUPDAYSNC() when basis is US 360 and settlement date is the last day of the month
* Ensure that all Financial function code uses the new Helpers class for Days Per Year
- Fix ISFORMULA() function to work with a cell reference to another worksheet
- Added calculation engine support for the new functions that were added in MS Excel 2013 and MS Excel 2016
- Text Functions
- CONCAT() Synonym for CONCATENATE()
- NUMBERVALUE() Converts text to a number, in a locale-independent way
- UNICHAR() Synonym for CHAR() in PHPSpreadsheet, which has always used UTF-8 internally
- UNIORD() Synonym for ORD() in PHPSpreadsheet, which has always used UTF-8 internally
- TEXTJOIN() Joins together two or more text strings, separated by a delimiter
- Logical Functions
- XOR() Returns a logical Exclusive Or of all arguments
- Date/Time Functions
- ISOWEEKNUM() Returns the ISO 8601 week number of the year for a given date
- Lookup and Reference Functions
- FORMULATEXT() Returns a formula as a string
- Engineering Functions
- ERF.PRECISE() Returns the error function integrated between 0 and a supplied limit
- ERFC.PRECISE() Synonym for ERFC
- Math and Trig Functions
- SEC() Returns the secant of an angle
- SECH() Returns the hyperbolic secant of an angle
- CSC() Returns the cosecant of an angle
- CSCH() Returns the hyperbolic cosecant of an angle
- COT() Returns the cotangent of an angle
- COTH() Returns the hyperbolic cotangent of an angle
- ACOT() Returns the cotangent of an angle
- ACOTH() Returns the hyperbolic cotangent of an angle
- Financial Functions
- PDURATION() Calculates the number of periods required for an investment to reach a specified value
- RRI() Calculates the interest rate required for an investment to grow to a specified future value