From 9e9f8e11bb2728db084038c1a34272931435c30f Mon Sep 17 00:00:00 2001
From: Igor Pashev <pashev.igor@gmail.com>
Date: Tue, 27 Jun 2017 07:02:26 +0300
Subject: Work with empty structures

---
 cmd/Main.hs            |  7 ++-----
 lib/Malodivo/Budget.hs | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/cmd/Main.hs b/cmd/Main.hs
index 7af6a83..dbe6dac 100644
--- a/cmd/Main.hs
+++ b/cmd/Main.hs
@@ -4,7 +4,6 @@ module Main
   ( main
   ) where
 
-import Control.Monad (when)
 import Data.Maybe (fromMaybe)
 import Data.Version (showVersion)
 import System.Environment (getArgs)
@@ -12,7 +11,6 @@ import System.Exit (die)
 
 import Data.Aeson (eitherDecode, encode)
 import qualified Data.ByteString.Lazy as L
-import qualified Data.HashMap.Strict as HM
 import System.Console.Docopt.NoTH
        (isPresent, longOption, parseArgsOrExit, parseUsageOrExit, usage)
 import Text.InterpolatedString.Perl6 (qc)
@@ -52,9 +50,8 @@ process = do
       let allBills = I.bills si
           suppliedFunds = di2df $ I.districts si
           ministryLimits = mi2ml $ fromMaybe [] (I.ministries si)
-      in do when (HM.null suppliedFunds) $ die "We needs at least one district"
-            L.putStr . encode . O.encode $
-              manyToManyLimited suppliedFunds ministryLimits allBills
+      in L.putStr . encode . O.encode $
+         manyToManyLimited suppliedFunds ministryLimits allBills
 
 main :: IO ()
 main = do
diff --git a/lib/Malodivo/Budget.hs b/lib/Malodivo/Budget.hs
index 3a68fdf..c063b2a 100644
--- a/lib/Malodivo/Budget.hs
+++ b/lib/Malodivo/Budget.hs
@@ -167,6 +167,12 @@ that some districts can pay their shares and others can't:
 >>> manyToOne low medium == low
 True
 
+
+It works without any districts specified:
+
+>>> manyToOne HM.empty medium
+fromList []
+
 -}
 manyToOne ::
      D.DistrictFunds -- ^ Amounts of available funds per district.
@@ -178,6 +184,30 @@ manyToOne df b = HM.fromList $ zip ds (normalizeDown (B.amount b) fs)
 
 {-|
 Districts funding multiple bills. No constraints.
+
+>>> :set -XOverloadedStrings
+>>> import qualified Data.HashMap.Strict as HM
+>>> import qualified Malodivo.Types.Bill as B
+>>> import qualified Malodivo.Types.District as D
+>>> import qualified Malodivo.Types.Ministry as M
+
+>>> let scienceA = B.Bill { B.amount = 10, B.name = "Science A", B.ministry = M.Science }
+>>> let welfareA = B.Bill { B.amount = 100, B.name = "Welfare A", B.ministry = M.Welfare }
+
+
+It works without any districts specified:
+
+>>> snd . head $  manyToMany HM.empty [scienceA]
+fromList []
+
+
+It works without bills:
+
+>>> manyToMany HM.empty []
+[]
+>>> let funds = HM.fromList [(D.Palolene, 100), (D.Lakos, 200)]
+>>> manyToMany funds []
+[]
 -}
 manyToMany ::
      D.DistrictFunds -- ^ Amounts of available funds per district.
-- 
cgit v1.2.3