Peace For All

August 29, 2006

Power comes at a price

Filed under: Programming — Devlin Bentley @ 2:47 pm

Going through the Python tutorial again:

Tuples can be used as keys if they contain only strings, numbers, or tuples; if a tuple contains any mutable object either directly or indirectly, it cannot be used as a key.

Well OK, that sounds reasonable.  You can’t use an object as a key if it keeps changing, right?

Oh wait, I can in Java.  I define a Hash function, done.

I have only had to use this once, and it was for a rather baroque situation, but it was rather cool that I could do it, and fairly simple as well.  Just pick which non-mutable instance variables of the class that should be used to generate a hash value, and shove them into a hash function.


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