Although we have ordered-collections,
a Map Int a introduces many levels of indirection; it's internally based on a binary/ternary tree for performing
lookups, and although very efficient for arbitrary key types that support total ordering, is not efficient for
a simple type like Int, which could capitalize on bitwise efficiency.
However, we also have Foreign.Object, which is just a javascript map, but acts like a Map String a - acting
as fast as javascript permits when performing lookups a' la foo["bar"].
This package is not intended to be performant with respect to Haskell's infamous IntMap in https://hackage.haskell.org/package/containers;
there is no amortized cost analysis or Patricia trees here; just a simple wrapper around Foreign.Object.
However, it is convenient for those of us who want to use numbers as keys, but don't want to do all the parsing and printing manually.