Hash tables and mutable keys, part two

(Part one is here.)

You know, I was so confident when writing the first post that I was addressing a common problem (which is not entirely untrue considering Google hits) and that it would be a pretty straightforward “here’s the issue, here’s the fix, enjoy” scenario.

Boy, was I wrong.

The common approach when trying to fix a bug is to first reproduce the problem. While I had no difficulty making a fictitious test case that does reproduce the “unreachable hashed entry” issue, I’m having all the trouble in the world finding a proper, real-world, justifiable algorithm that needs a hash table with mutable keys.
It just never seems to me like a reasonable thing to do.

Nevertheless, being the stubborn bastard that I am, I’ll present here a recipe to encounter the problem with as much justifications as I could make up. And if ever you’re ever stuck in a situation where you do need a hash set to react properly with mutable entries, well you’ll have a solution of sorts.

Take a deep breath (this is a looooong one) and hit the jump.

Continue reading Hash tables and mutable keys, part two

Hash tables and mutable keys, part one

In this little series of posts (probably two three), I’m going to address a problem that has happened to me yesterday and was a real blocker in my algorithm : how to get a hash table (HashSet or Dictionary) to work with keys that change their hash code over time.

Continue reading Hash tables and mutable keys, part one