1 files changed, 18 insertions, 0 deletions
diff --git a/src/Assignment.hs b/src/Assignment.hs
index c086280..51e619a 100644
--- a/src/Assignment.hs
+++ b/src/Assignment.hs
@@ -5,6 +5,24 @@ import qualified Expr as E
 data Assignment
     = Variable String E.Expr
     | Function String String E.Expr
+    deriving (Eq)
+
+name :: Assignment -> String
+name (Variable n _) = n
+name (Function n _ _) = n
+
+type Context = [Assignment]
+
+update :: Context -> Assignment -> Context
+update context a
+  | name a `elem` map name context = map replaceIf context
+  | otherwise = a:context
+  where replaceIf a' = if name a' == name a then a else a'
+
+get :: Context -> String -> Maybe Assignment
+get context n = case found of [] -> Nothing
+                              [a] -> Just a
+    where found = filter (\a -> name a == n) context
 
 instance Show Assignment where
     show (Variable name e) = name ++ " = " ++ show e