The string to convert from
Specification:
sign ::= + | - digit ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 indicator ::= e | E digits ::= digit [digit]... decimal-part ::= digits . [digits] | [.] digits exponent-part ::= indicator [sign] digits infinity ::= Infinity | Inf nan ::= NaN numeric-value ::= decimal-part [exponent-part] | infinity numeric-string ::= [sign] numeric-value | [sign] nan
invalidOperation is flagged when str is not a valid string
Converts a string representing a number to an exact decimal.
If the string does not represent a number, then the result is NaN and invalidOperation is true.