1 files changed, 41 insertions, 0 deletions
diff --git a/distrib/compare/BuildInfo.hs b/distrib/compare/BuildInfo.hs
new file mode 100644
index 0000000000..547e5ac853
--- /dev/null
+++ b/distrib/compare/BuildInfo.hs
@@ -0,0 +1,41 @@
+
+module BuildInfo where
+
+import Control.Monad.State
+
+data BuildInfo = BuildInfo {
+                     biThingVersionMap :: ThingVersionMap,
+                     biWays :: Ways
+                 }
+-- Mapping from thing (e.g. "Cabal") to version (e.g. "1.10.0.0")
+type ThingVersionMap = [(String, String)]
+-- The list of ways in the order the build system uses them, e.g.
+-- ["v", "p", "dyn"] => we have ".depend-v-p-dyn.haskell" files
+type Ways = [String]
+
+addThingVersion :: ThingVersionMap -> String -> String -> Maybe ThingVersionMap
+addThingVersion mapping thing version
+ = case lookup thing mapping of
+   Just version' ->
+       if version == version'
+       then Just mapping
+       else Nothing
+   Nothing ->
+       Just ((thing, version) : mapping)
+
+getThingVersionMap :: State BuildInfo ThingVersionMap
+getThingVersionMap = do st <- get
+                        return $ biThingVersionMap st
+
+getWays :: State BuildInfo Ways
+getWays = do st <- get
+             return $ biWays st
+
+putThingVersionMap :: ThingVersionMap -> State BuildInfo ()
+putThingVersionMap tm = do st <- get
+                           put $ st { biThingVersionMap = tm }
+
+putWays :: Ways -> State BuildInfo ()
+putWays ws = do st <- get
+                put $ st { biWays = ws }
+