diff --git a/nix/lib.nix b/nix/lib.nix
index 0fe10056b..642dd510f 100644
--- a/nix/lib.nix
+++ b/nix/lib.nix
@@ -20,10 +20,13 @@ in rec {
     phases = [ "buildPhase" ];
   };
 
+  # Generate a nix file from an opam file
   opam2nix = { src, opamFile ? findOpamFile src, ... }@args:
     pkgs.runCommandNoCC (args.pname or opamFile + ".nix") args
     "cat ${src}/${opamFile} | ${pkgs.glibc.bin}/bin/iconv -c -f utf-8 -t ascii | ${opam-parser} > $out";
 
+  # Traverse OPAM repository, producing an extension to
+  # ocamlPackages than includes all the packages in the repo.
   traverseOPAMRepo = repo: self: super:
     let
       pkgNames = builtins.readDir "${repo}/packages";
@@ -53,6 +56,7 @@ in rec {
         }) pkgNames;
     in opamPkgs;
 
+  # Same as traverseOPAMRepo, but packages in super take precedence over packages from the new repo.
   traverseOPAMRepo' = repo: self: super:
     let traversed = traverseOPAMRepo repo self super;
     in traversed // builtins.mapAttrs (name: v:
@@ -60,6 +64,7 @@ in rec {
         versions = (traversed.${name} or { versions = { }; }).versions;
       }) super;
 
+  # Extension that adds callOPAMPackage to the package set
   callOPAMPackage = self: super: {
     callOPAMPackage = src: newAttrs: overrides:
       (self.callPackage (opam2nix (newAttrs // { inherit src; }))
diff --git a/nix/opam-parser.hs b/nix/opam-parser.hs
index 1dafb875f..b4a4d8cb3 100644
--- a/nix/opam-parser.hs
+++ b/nix/opam-parser.hs
@@ -19,6 +19,8 @@ data OPAM
   , checkPhase :: Maybe [[String]]
   , source :: Maybe String
   } deriving Show
+
+-- Turn a description into a nix file
 opam2nix :: OPAM -> String
 opam2nix OPAM {..} =
   let
@@ -62,6 +64,7 @@ opam2nix OPAM {..} =
 update :: Maybe a -> a -> Maybe a
 update old new = if isNothing old then Just new else old
 
+-- Evaluate a Field and update OPAM description accordingly
 evaluateField :: OPAM -> Field -> OPAM
 evaluateField o@OPAM {..} = \case
   Name s -> o { name = update name s }
@@ -86,29 +89,18 @@ evaluateField o@OPAM {..} = \case
 evaluateFields :: OPAM -> [Field] -> OPAM
 evaluateFields = foldl evaluateField
 
+
+-- Descriptions for various Fields of an opam file
+
 data Package
   = Package
   { identifier :: String
   , additionalPackageInfo :: [String]
   } deriving Show
 
+-- An expression as found in a Command
 data Exp = Str String | Var String deriving Show
 
-data Command
-  = Command
-  { command :: [Exp]
-  , additionalCommandInfo :: [String]
-  } deriving Show
-
-data Field
-  = Name String
-  | Version String
-  | Depends [Package]
-  | Build [Command]
-  | URL String
-  | Other String
-  deriving Show
-
 evaluateExp :: Exp -> String
 evaluateExp =
   let
@@ -126,9 +118,27 @@ evaluateExp =
       Var "jobs" -> "1"
       Var s -> "${"<>s<>"}"
 
+data Command
+  = Command
+  { command :: [Exp]
+  , additionalCommandInfo :: [String]
+  } deriving Show
+
+data Field
+  = Name String
+  | Version String
+  | Depends [Package]
+  | Build [Command]
+  | URL String
+  | Other String
+  deriving Show
+
+
+-- An opam file is a collection of fields,
 opamFile :: ParsecT String u Identity [Field]
 opamFile = many field <* eof
 
+-- Each has a name and a type;
 field :: ParsecT String u Identity Field
 field = Name <$> fieldParser "name" stringParser
     <|> Version <$> fieldParser "version" stringParser
@@ -137,40 +147,43 @@ field = Name <$> fieldParser "name" stringParser
     <|> sectionParser "url" (URL <$> (fieldParser "src" stringParser <* many (noneOf "}")))
     <|> Other <$> (many (noneOf "\n") <* char '\n')
 
+-- Field's structure is "name: value"
 fieldParser :: String -> ParsecT String u Identity t -> ParsecT String u Identity t
 fieldParser name valueParser = try $ between (string (name<>":") >> many (oneOf " \n")) (many $ oneOf " \n") valueParser <* commentParser
 
+-- Sections's structure is "name { fields }"
 sectionParser :: String -> ParsecT String u Identity t -> ParsecT String u Identity t
 sectionParser name valueParser = try $ between (string name >> many (oneOf " ") >> string "{" >> many (oneOf " \n")) (many (oneOf " \n") >> char '}' >> char '\n') valueParser
 
+-- String is enclosed in quotes
 stringParser :: ParsecT String u Identity String
 stringParser = between (char '"') (char '"') (many $ noneOf "\"")
 
+-- Expression is either a string or a variable
 expParser :: ParsecT String u Identity Exp
 expParser = try (Str <$> stringParser)
         <|> Var <$> many1 (noneOf " \n\"{}[]")
 
+-- "Additional Info" is additional information about a package or command, "{like-this}"
 additionalInfoParser :: ParsecT String u Identity [String]
 additionalInfoParser = option [] $ try
   $ between (many (char ' ') >> char '{') (char '}')
   ((many $ noneOf " &}") `sepBy` (oneOf " &"))
 
+-- Command is a [expressions] with additionional information
 commandParser :: ParsecT String u Identity Command
-commandParser = do
-  command <- listParser $ try expParser
-  additionalInfo <- additionalInfoParser
-  return $ Command command additionalInfo
+commandParser = Command <$> (listParser $ try expParser) <*> additionalInfoParser
 
+-- Comment starts with # and goes to the end of line
 commentParser :: ParsecT String u Identity ()
 commentParser = optional $ do
   void $ string "#"
   many $ noneOf "\n"
 
+-- Package is a "string" with additional information
 packageParser :: ParsecT String u Identity Package
-packageParser = do
-  name <- stringParser
-  additionalInfo <- additionalInfoParser
-  return $ Package name additionalInfo
+packageParser = Package <$> stringParser <*> additionalInfoParser
+
 
 listParser :: ParsecT String u Identity t -> ParsecT String u Identity [t]
 listParser valueParser =