From: Norman Ramsey <nr@eecs.harvard.edu>
Date: Sun, 17 Sep 2006 00:34:10 +0000 (+0000)
Subject: do notation for the Maybe monad
X-Git-Tag: 2007-11-11~48
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=9252667140f745b407796f8a465690422cd5ce86;p=ghc-hetmet.git

do notation for the Maybe monad
---

diff --git a/utils/ghctags/GhcTags.hs b/utils/ghctags/GhcTags.hs
index 2defe75..a011a9d 100644
--- a/utils/ghctags/GhcTags.hs
+++ b/utils/ghctags/GhcTags.hs
@@ -201,12 +201,10 @@ graphData session graph =
     where foundthings ms =
               let filename = msHsFilePath ms
               in  do mod <- checkModule session (moduleName $ ms_mod ms)
-                     return $ case mod of
-                       Nothing -> FileData filename []
-                       Just m -> case renamedSource m of
-                                   Nothing -> FileData filename []
-                                   Just s -> fileData filename s
-
+                     return $ maybe (FileData filename []) id $ do
+                       m <- mod
+                       s <- renamedSource m
+                       return $ fileData filename s
 
 fileData :: FileName -> RenamedSource -> FileData
 fileData filename (group, imports, lie) =