Implemented binary equality operator

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
+data BinaryOperator = LogicalAnd | LogicalOr | LogicalEquality
     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"]
               }
 
@@ -61,6 +61,9 @@ 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))
             ],
@@ -93,4 +96,5 @@ 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)