  Despite recent advances in communication and automation, regulations are
still written in natural-language prose, subject to ambiguity, inconsistency,
and incompleteness. How can we craft regulations with precision? Our solution
is embodied in Eiger, a domain-specific programming language embedded in
Haskell. A domain expert pairs with a software engineer to write regulations in
Eiger. The domain expert needs only to read and audit the code, but not write
it. A first, limited, user study suggests that this works well in practice
because Eiger code mostly looks like Excel formulas with simple SQL queries.
  Eiger forms the kernel of a new strategy to deliver value to clients in our
professional services business with increased automation and precision. The
framework is executable: based on client data, we can use Eiger both to deduce
how best to adapt to a new regulation and then maintain compliance. This paper
reviews the design of Eiger and walks through its implementation. To preserve a
straightforward surface syntax but with monadic semantics, we have leveraged
advanced features, including GHC.Generics, the new OverloadedRecordDot
extension, and a novel approach to performing class instance selection at
run-time.
