Conversion between decimal numbers and Coq strings
Pretty straightforward, which is precisely the point of the
Decimal.int datatype. The only catch is
Decimal.Nil : we could
choose to convert it as
"" or as
"0". In the first case, it is
awkward to consider "" (or "-") as a number, while in the second case
we don't have a perfect bijection. Since the second variant is implemented
thanks to the first one, we provide both.
Warning! (-0) won't parse (compatibility with the behavior of Z).