aristidb / sequential-index

[Haskell] Sequential index numbers between 0.0 and 1.0 that allow arbitrarily inserting new numbers in between (for special containers).

Sequential index numbers between 0.0 and 1.0 that allow arbitrarily inserting new numbers in between. They can possibly used for disk-based and other special containers, where adding a new element without changing the indexes of the other elements is important.

Conceptually, SequentialIndex denotes a path to an element in an imaginary binary tree, with a '1' at the end. Except for 0.0 and 1.0, which are logically on the left or on the right of the entire tree.

So logically, the tree looks roughly like this:

0.0                          1.0
                            /
                /----------/
              0.1
              / \
          /--/   \--\
         /           \
       0.01         0.11
       / \          / \
  0.001   0.011     ...

Note that 0.0 is not connected to any other node, but it is still logically smaller than all nodes.