tryParseDanish "tyvetyve" returns 40

[ploeh]

tryParseDanish "tyvetyve" returns Some 40, which is surprising to say the least. It was never an explicit test case, though, but is a fairly standard idiom in the language, particularly when referring to years:

• nitten-fireogfirs (1984)
• tyve-seksten (2016)
• atten-fireogtres (1864)

There are two potential ways to address such numbers:

1. If they are unambiguous, a better result from tryParseDanish "tyvetyve" would be Some 2020. While I suspect that they are unambiguous, anyone can, and is welcome to, prove me wrong with only a single counter-example.
2. If such numerals are ambiguous, the correct return value would be None.

[ploeh]

Similar to #28