Issue with French culture

[OhSoGood]

Hi,

I've been happily using SmartFormat for a while (thank you very much for it!), just to realize I was always on English culture (I'm using SmartFormat v2.7 on .NET 4.7).

Switching to French, I realized that the implementation of PluralRules.DualFromZeroToTwo (used in French) did not take into account the 'c' parameter like PluralRules.DualOneOther (used in English).

Ex:
Smart.Format("{0:|One item|Two items}", 1") returns 'One item' as expected, but
Smart.Format(new CultureInfo("fr"), "{0:|Un objet|Deux objets}", 1") returns an empty string instead of 'Un objet'.

This is because DualFromZeroToTwo is too simplistic and should be written like DualOneOther.

// This is DualOneOther original code
private static PluralRuleDelegate DualOneOther => (n, c) =>
        {
            if (c == 2) return n == 1 ? 0 : 1;
            if (c == 3) return n == 0 ? 0 : n == 1 ? 1 : 2;
            if (c == 4) return n < 0 ? 0 : n == 0 ? 1 : n == 1 ? 2 : 3;
            return -1;
        };// Dual: one (n == 1), other

// This is my proposal for DualFromZeroToTwo 
private static PluralRuleDelegate DualFromZeroToTwo => (n, c) => 
        {
            if (c == 2) return n < 2 ? 0 : 1;
            if (c == 3) return n == 0 ? 0 : n < 2 ? 1 : 2;
            if (c == 4) return n < 0 ? 0 : n == 0 ? 1 : n < 2 ? 2 : 3;
            return -1;
        };// DualFromZeroToTwo: one (n == 0..2 fractionate and n != 2), other

In the meantime, I'll stick to English as the current lib's code is erroneous for French and other 'DualFromZeroToTwo' cultures.

[axunonb]

Thanks for pointing this out.
As a matter of fact, the PluralRules logic is as much as untested. The high test coverage is misleading here. Although you wrote "issue with French culture", isn't it an issue with the DualFromZeroToTwo delegate, unless French required a different rule?
We'd be more than happy about a PR on that.

[OhSoGood]

Yes, you are right, as I wrote, the code is erroneous for French and other 'DualFromZeroToTwo' cultures, the issue is about the DualFromZeroToTwo delegate. I mentioned the French culture as I found the issue using that culture actually.

For the PR, my github environment is broken these days, so it may be faster and easier if you commit & push directly.

[axunonb]

Fix will go into v3.0