Translating a C++ parser to Haskell

Recently I translated Nix's derivation parser to Haskell and I thought this would make an instructive example for how C++ idioms map to Haskell idioms. This post targets people who understand Haskell's basic syntax but perhaps have difficulty translating imperative style to a functional style. I will also throw in some benchmarks at the end, too, comparing Haskell performance to C++. Nix derivatio