[commit: base] master: Comments (a97ebe3)

[Ian Lynagh]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

https://github.com/ghc/packages-base/commit/a97ebe39e8b76ca1dad1e875609da89e81353c6e

>---------------------------------------------------------------

commit a97ebe39e8b76ca1dad1e875609da89e81353c6e
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Thu Jun 6 14:36:56 2013 +0100

    Comments

>---------------------------------------------------------------

 GHC/Exception.lhs-boot |   23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/GHC/Exception.lhs-boot b/GHC/Exception.lhs-boot
index 9c3b0bf..f93d806 100644
--- a/GHC/Exception.lhs-boot
+++ b/GHC/Exception.lhs-boot
@@ -1,3 +1,24 @@
+This SOURCE-imported hs-boot module cuts a big dependency loop:
+
+         GHC.Exception
+imports  Data.Maybe
+imports  GHC.Base
+imports  GHC.Err
+imports  {-# SOURCE #-} GHC.Exception
+
+More dramatically
+
+         GHC.Exception
+imports  Data.Typeable
+imports  Data.Typeable.Internals
+imports  GHC.Arr (fingerprint representation etc)
+imports  GHC.Real
+imports  {-# SOURCE #-} GHC.Exception
+
+However, GHC.Exceptions loop-breaking exports are all nice,
+well-behaved, non-bottom values.  The clients use 'raise#'
+to get a visibly-bottom value.
+
 \begin{code}
 {-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE NoImplicitPrelude #-}
@@ -11,8 +32,6 @@ module GHC.Exception ( SomeException, errorCallException,
     ) where 
 import GHC.Types( Char )
 
--- These exports are nice, well-behaved, non-bottom values
-
 data SomeException
 divZeroException, overflowException, ratioZeroDenomException  :: SomeException
 errorCallException :: [Char] -> SomeException