diff --git a/common/PrettyShow.hs b/common/PrettyShow.hs
index 84713b5..1377831 100644
--- a/common/PrettyShow.hs
+++ b/common/PrettyShow.hs
@@ -20,6 +20,15 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 -- This ought to use a class (like show does), so that it can be extended
 -- properly without me needing to have Tock-specific cases in here -- see the
 -- appropriate SYB paper.
+--
+-- PrettyShow exports two functions: pshow and pshowCode.  pshow works
+-- much like 'gshow', but it uses the 'Text.PrettyPrint.HughesPJ' module
+-- to render the text with line-breaks and such.
+--
+-- pshowCode uses the 'ShowOccam' and 'ShowRain' type-classes wherever possible
+-- (via the 'extCode' function) to print out data, otherwise it acts
+-- like pshow.  Note that because pshowCode chooses the appropriate
+-- language based on the 'csFrontend' in 'CompState', it is inside the CSM monad.
 module PrettyShow (pshow, pshowCode) where
 
 import Control.Monad.State
diff --git a/common/ShowCode.hs b/common/ShowCode.hs
index 9ad109b..38d2d9a 100644
--- a/common/ShowCode.hs
+++ b/common/ShowCode.hs
@@ -19,7 +19,7 @@ with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 -- | A module with type-classes and functions for displaying code, dependent on the context.
 -- Primarily, this means showing code as occam in error messages for the occam frontend, and Rain code for the Rain frontend.
-module ShowCode where 
+module ShowCode (showCode, showOccam, showRain, formatCode, extCode) where 
 
 import Control.Monad.State
 import Data.Generics
@@ -176,6 +176,12 @@ instance ShowRain A.Variable where
   showRain x = "<invalid Rain variable: " ++ show x ++ ">"
 
 -- | Extends an existing (probably generic) function with cases for everything that has a specific ShowOccam and ShowRain instance
+-- This is a bit of manual wiring.  Because we can't generically deduce whether or not 
+-- a given Data item has a showRain/showOccam implementation (that I know of), I have 
+-- had to add this function that has a line for each type that does have a 
+-- ShowOccam/ShowRain implementation.  But since to add a type to the ShowOccam/ShowRain 
+-- classes you have to provide a specific instance above anyway, I don't think that adding 
+-- one more line while you're at it is too bad.
 extCode :: Typeable b => (b -> Doc) -> (forall a. (ShowOccam a, ShowRain a) => a -> String) -> (b -> Doc)
 extCode q f = q `extQ` (text . (f :: A.Type -> String))
                 `extQ` (text . (f :: A.DyadicOp -> String))