Performing fast comparisons between data types

The StableName package allows us to establish constant time comparisons of arbitrary data types. The Hackage documentation elegantly describes this (http://hackage.haskell.org/package/base-4.7.0.0/docs/System-Mem-StableName.html):

"Stable names solve the following problem: suppose you want to build a hash table with Haskell objects as keys, but you want to use pointer equality for comparison; maybe because the keys are large and hashing would be slow, or perhaps because the keys are infinite in size. We can't build a hash table using the address of the object as the key, because objects get moved around by the garbage collector, meaning a re-hash would be necessary after every garbage collection."

How to do it…

1. Import the built-in StableName package as follows:

   import System.Mem.StableName

2. Create a custom data type as follows:

   data Point = Point [Int]

3. In main, define two points as follows:

     main = do
       let p1 = Point [1..]
       let p2 = Point [2,4...