diff --git a/src/Lib.hs b/src/Lib.hs
index e4ecfed..30242ee 100644
--- a/src/Lib.hs
+++ b/src/Lib.hs
@@ -34,7 +34,7 @@ import Data.Functor.Identity
 
 data Expression = Constant Bool | Binary BinaryOperator Expression Expression | Unary UnaryOperator Expression | Variable String
     deriving Show
-data BinaryOperator = LogicalAnd | LogicalOr | LogicalEquality
+data BinaryOperator = LogicalAnd | LogicalOr | LogicalEquality | LogicalImplication
     deriving Show
 data UnaryOperator  = LogicalNot
     deriving Show
@@ -44,9 +44,9 @@ def = emptyDef{ commentStart = ""
               , commentEnd = ""
               , identStart = letter <|> char '_'
               , identLetter = alphaNum <|> char '_'
-              , opStart = oneOf "&|~="
-              , opLetter = oneOf "&|~="
-              , reservedOpNames = ["&", "|", "~", "="]
+              , opStart = oneOf "&|~=-"
+              , opLetter = oneOf "&|~=-><"
+              , reservedOpNames = ["&", "|", "~", "=", "->", "<-->"]
               , reservedNames = ["true", "false"]
               }
 
@@ -61,9 +61,6 @@ exprparser = buildExpressionParser table term <?> "expression"
 
 table :: [[Operator String u Identity Expression]]
 table = [
-            [
-                Infix (m_reservedOp "=" >> return (Binary LogicalEquality)) AssocLeft
-            ],
             [
                 Prefix (m_reservedOp "~" >> return (Unary LogicalNot))
             ],
@@ -72,6 +69,15 @@ table = [
             ],
             [
                 Infix (m_reservedOp "|" >> return (Binary LogicalOr)) AssocLeft
+            ],
+            [
+                Infix (m_reservedOp "->" >> return (Binary LogicalImplication)) AssocLeft
+            ],
+            [
+                Infix (m_reservedOp "<-->" >> return (Binary LogicalEquality)) AssocLeft
+            ],
+            [
+                Infix (m_reservedOp "=" >> return (Binary LogicalEquality)) AssocLeft
             ]
         ]
 
@@ -92,9 +98,14 @@ collectVariableNames (Unary _ right)       = collectVariableNames right
 collectVariableNames (Variable name)       = Set.singleton name
 
 evaluate :: Map String Bool -> Expression -> Bool
-evaluate _  (Constant b)                   = b
-evaluate vs (Unary    LogicalNot      e)   = not (evaluate vs e)
-evaluate vs (Binary   LogicalAnd      l r) = evaluate vs l && evaluate vs r
-evaluate vs (Binary   LogicalOr       l r) = evaluate vs l || evaluate vs r
-evaluate vs (Binary   LogicalEquality l r) = evaluate vs l == evaluate vs r
-evaluate vs (Variable name)                = maybe False id (Map.lookup name vs)
+evaluate _  (Constant b)                      = b
+evaluate vs (Unary    LogicalNot         e)   = not (evaluate vs e)
+evaluate vs (Binary   LogicalAnd         l r) = evaluate vs l && evaluate vs r
+evaluate vs (Binary   LogicalOr          l r) = evaluate vs l || evaluate vs r
+evaluate vs (Binary   LogicalEquality    l r) = evaluate vs l == evaluate vs r
+evaluate vs (Binary   LogicalImplication l r) = implication (evaluate vs l) (evaluate vs r)
+    where
+        implication :: Bool -> Bool -> Bool
+        implication False True = False
+        implication _     _    = True
+evaluate vs (Variable name)                   = maybe False id (Map.lookup name vs)