How to parse Quoted Quote?

[benjamin-hodgson]

How to parse Quoted Quote?

[joonhwan]

Thanks. your answers are always well organized and good literature as well as your library itself.

[benjamin-hodgson]

You're almost there. The problem is what happens when your parser encounters the single " at the end of the input. The first branch of the Or, Sequence('"','"'), consumes the ", so the parsing process commits to that branch. Then when it fails to see the second " it fails. Because it's committed to the left branch, it doesn't try the right branch and the whole parser fails.

You just need to apply the Try operator, which tells the parser "don't commit to this branch". When a Try parser fails, it backtracks so that another branch of the Or can be tried.

Parser<char, string> stringLiteral = Try(String("\"\"")).ThenReturn('"')  // note use of Try
    .Or(Token(c => c != '"'))
    .ManyString()
    .Between(Char('"'));