Request for Language: Tree Language for number formatting

A Tree Language that compiles to this (or implements it's own logic)
https://github.com/d3/d3-format would be nice.

It would have the advantage that it would be self-documenting.

Start with the d3-format project linked in the issue and inspect the repository's current Tree Language implementation. Define the supported number-formatting behavior and a representative example; done means the Tree Language provides the requested self-documenting formatting capability.

Written by the indexing model from the issue text.