OK, it may be an old question but why doesn't HN search for old URLs before allowing you to post? I missed this the first time around and am really glad that it got posted (and glad you found the dupes) but most reposts are bad. I think something like a URL check would be valuable.

There is a URL check, but it only finds exact matches, and only if the URL tested against is in memory. If it's old enough and hasn't been accessed recently, it's not found.

I thought this was in jacquesm's FAQ, but it appears not to be:

http://jacquesmattheij.com/The+Unofficial+HN+FAQ

You might suggest it to him, although he's very busy.

Also this: http://www.reddit.com/r/programming/comments/8ufl1/gray_code...