Test findHighestVar

+ And fix bug with findHighestVar

Author: rasheedja

src/Linear/Simplex/Types.hs

@@ -341,6 +341,17 @@ type SimpleSystem = [SimpleConstraint]
 simplifySimpleSystem :: SimpleSystem -> SimpleSystem
 simplifySimpleSystem = map simplifySimpleConstraint
 
+findHighestVar :: SimpleSystem -> Var
+findHighestVar simpleSystem =
+  let
+    vars = [v | gc <- simpleSystem,
+                term <- exprToList $ getGenericConstraintLHS gc,
+                v <- case term of
+                       VarTerm v -> [v]
+                       CoeffTerm _ v -> [v]
+                       _ -> []]
+  in maximum vars
+
 data StandardFormRow = StandardFormRow
   { lhs :: Expr
   , rhs :: SimplexNum
@@ -406,9 +417,6 @@ removeUselessSystemBounds constraints bounds =
   )
   constraints
 
-findHighestVar :: SimpleSystem -> Var
-findHighestVar = maximum . map (maximum . map (\case (CoeffTerm _ v) -> v; _ -> 0) . exprToList . getGenericConstraintLHS)
-
 -- | Eliminate negative lower bounds via substitution
 -- Return the system with the eliminated variables and a map of the eliminated variables to their equivalent expressions
 -- First step here https://en.wikipedia.org/wiki/Simplex_algorithm#Standard_form

test/Linear/Simplex/TypesSpec.hs

@@ -539,6 +539,32 @@ spec = do
                 <> show simplifiedSimpleSystemEval
             ) $
             simpleSystemEval == simplifiedSimpleSystemEval
+    it "findHighestVar finds the highest variable in a simple system" $ do
+      let simpleSystem1 =
+            [ Expr (VarTerm 0) :>= 0
+            , Expr (VarTerm 0) :<= 1
+            , Expr (VarTerm 1) :>= 0
+            , Expr (VarTerm 1) :<= 1
+            ]
+          simpleSystem100 =
+            [ Expr (VarTerm 0) :<= 1
+            , Expr (VarTerm 50) :<= 1
+            , Expr (VarTerm 100) :<= 1
+            ]
+          simpleSystem10 =
+            [ Expr (VarTerm (-10)) :<= 1
+            , Expr (VarTerm 0) :<= 1
+            , Expr (VarTerm 10) :<= 1
+            ]
+          simpleSystemMinus10 =
+            [ Expr (VarTerm (-10)) :<= 1
+            , Expr (VarTerm (-20)) :<= 1
+            ]
+          
+      findHighestVar simpleSystem1 `shouldBe` 1
+      findHighestVar simpleSystem100 `shouldBe` 100
+      findHighestVar simpleSystem10 `shouldBe` 10
+      findHighestVar simpleSystemMinus10 `shouldBe` (-10)
   describe "Bounds" $ do
     it "validateBounds finds that deriving bounds for a system where -1 <= x <= 1 has valid bounds" $ do
       let simpleSystem =
@@ -691,4 +717,3 @@ spec = do
           simplifiedSimpleSystem = removeUselessSystemBounds simpleSystem bounds
           expectedSimpleSystem = [Expr (VarTerm 0) :<= 2, Expr (CoeffTerm 2 0) :<= 6]
       simplifiedSimpleSystem `shouldBe` expectedSimpleSystem
-