Request: Document the isanswered search parameter on the advanced search help page.

##Update

This has been implemented by adding the following to the help page:

isanswered: yes/true/1 returns only questions that have at least one accepted or positively-scored answer; no/false/0 returns only questions with no accepted or positively-scored answers.

Unfortunately, the above is incorrect: acceptances are ignored by this search. The correct description would be:

isanswered: yes/true/1 returns only questions that have at least one positively-scored answer; no/false/0 returns only questions with no positively-scored answers.

###Rationale

From time to time users ask about searching for questions that are unanswered-in-SE-sense (no accepted answer and no positively scored answer). For example, Deduplicator asked yesterday:

What about adding a new operator to search, which restricts the same way as the unanswered page?

The older thread on this is How to search unanswered questions where the answers include: using hasaccepted:0, using answers:0. There is also a feature request there to have ascore:0 parameter to handle the presence of answers with positive score.

Yet, all this time SE did have a search parameter for filtering questions based on answer score: isanswered. As m0sa explained, its logic is actually hasAnswerWithScoreGreaterThanZero

Thus, the combination isanswered:0 hasaccepted:0 closed:0 matches SE definition of an unanswered question.

For example, this search nearly matches the questions/unanswered view on Stack Overflow. (The numbers are not exactly the same, either because of caching or because of some narrow edge cases; for practical purposes the results are the same.

One can now filter by tags and/or question score, then sort by dates, etc... like you always wanted. For example, when I'm feeling generous, I combine this search with intags:mine and answers:1.. to review answers on unanswered questions and maybe upvote them, taking the question out of unanswered.