- 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
By design, UTF-8 allows any byte-oriented substring searching algorithm,
since the sequence of bytes for a character cannot occur anywhere else
([source](https://en.wikipedia.org/wiki/UTF-8#Advantages_3)).
So `str_replace()` also works for UTF-8-encoded strings, assuming that
the input strings are valid UTF-8 strings. The previous implementation
of mbStrReplace() did nothing to detect invalid strings.
Also, `str_replace()` does not support [Unicode equivalence](https://en.wikipedia.org/wiki/Unicode_equivalence),
but nor do the other `mb_string` functions, and nor does `=SUBSTITUTE()` in Excel
(tested on Excel for Mac version 15.19.1, Excel 2016 for Windows and LibreOffice 5.1).
Closes#109
Adrien Crivelli