map a signedIntString into a BigInt
a single base 10 digit
one or more digit chars
zero or more digit chars
A string matching the json specification for numbers.
A string matching the json specification for numbers. from: https://tools.ietf.org/html/rfc4627
A String of either 1 '0' or 1 non-zero digit followed by zero or more digits
a single base 10 digit excluding 0
A nonNegativeIntString possibly preceded by '-'