Additional of Assignment and some changes in the types.

src/Types/Assignment.hs

@@ -0,0 +1,12 @@
+module Types.Assignment where
+
+import qualified Data.Map as M
+import qualified Types.Payer as P
+import qualified Types.Bill as B
+import qualified Types.Interval as I
+
+type Assignment = M.Map B.Bill Participation
+data Participation = Participation P.Payer I.Interval
+
+assign :: P.Payer -> I.Interval -> B.Bill -> Assignment -> Assignment
+assign p i b a = M.insert b (Participation p i) a

src/Types/Bill.hs

@@ -10,8 +10,9 @@ import qualified Data.Label as L
 
 data Bill = Bill
     { _screenName    :: T.Text
-    , _interval      :: I.Interval
+    , _interval      :: Maybe I.Interval
     , _totalValue    :: V.Value
     } deriving (Eq, Ord)
 
-L.mkLabels [''Bill]
+L.mkLabels [''Bill]
+

src/Types/Payer.hs

@@ -4,22 +4,32 @@ module Types.Payer where
 
 import qualified Data.Text as T
 import qualified Data.Map.Strict as M
-import qualified Types.Bill as B
+import qualified Types.Bill as B (Bill)
 import qualified Data.Label as L
 import qualified Types.Interval as I (Interval)
+import qualified Types.Value as V (Value)
 
 data Payer = Payer
     { _screenName    :: T.Text
-    , _bills         :: M.Map B.Bill I.Interval
+    , _bills         :: M.Map B.Bill (Proportion, I.Interval)
     } deriving (Eq)
 
+-- | 'Proportion' of 'Bill' that a 'Payer' pays.
+type Proportion = Rational
+
 L.mkLabels [''Payer]
 
+-- | Creates a new 'Payer' with an empty list of 'Bill's.
 newPayer :: T.Text -> Payer
 newPayer name = Payer name M.empty
 
-addBill' :: B.Bill -> I.Interval -> M.Map B.Bill I.Interval -> M.Map B.Bill I.Interval
-addBill' b i bs = M.insert b i bs
+addBill' :: B.Bill -> Proportion -> I.Interval -> M.Map B.Bill (Proportion, I.Interval) -> M.Map B.Bill (Proportion, I.Interval)
+addBill' b prop i bs = M.insert b (prop, i) bs
 
-addBill :: B.Bill -> I.Interval -> Payer -> Payer
-addBill b i p = L.modify bills (addBill' b i) p
+-- | Add a new 'Bill' to the 'Payer'.
+addBill :: B.Bill -> Proportion -> I.Interval -> Payer -> Payer
+addBill b prop i p = L.modify bills (addBill' b prop i) p
+
+-- | Computer the cost of a particular 'Bill' for the 'Payer'.
+costOf :: Payer -> B.Bill -> V.Value
+costOf p b = undefined