Test/TestParser.hs

@@ -144,6 +144,21 @@ testExpressionPreIncrement = TestCase $
 testExpressionPreDecrement = TestCase $
     assertEqual "expect PreIncrement" (UnaryOperation PreDecrement (Reference "a")) $
     parseExpression [DECREMENT,IDENTIFIER "a"]
+testExpressionAssign = TestCase $
+    assertEqual "expect assign 5 to a" (StatementExpressionExpression (Assignment (Reference "a") (IntegerLiteral 5))) $
+    parseExpression [IDENTIFIER "a",ASSIGN,INTEGERLITERAL 5]
+testExpressionTimesEqual = TestCase $
+    assertEqual "expect assign and multiplication" (StatementExpressionExpression (Assignment (Reference "a") (BinaryOperation Multiplication (Reference "a") (IntegerLiteral 5)))) $
+    parseExpression [IDENTIFIER "a",TIMESEQUAL,INTEGERLITERAL 5]
+testExpressionDivideEqual = TestCase $
+    assertEqual "expect assign and division" (StatementExpressionExpression (Assignment (Reference "a") (BinaryOperation Division (Reference "a") (IntegerLiteral 5)))) $
+    parseExpression [IDENTIFIER "a",DIVEQUAL,INTEGERLITERAL 5]
+testExpressionPlusEqual = TestCase $
+    assertEqual "expect assign and addition" (StatementExpressionExpression (Assignment (Reference "a") (BinaryOperation Addition (Reference "a") (IntegerLiteral 5)))) $
+    parseExpression [IDENTIFIER "a",PLUSEQUAL,INTEGERLITERAL 5]
+testExpressionMinusEqual = TestCase $
+    assertEqual "expect assign and subtraction" (StatementExpressionExpression (Assignment (Reference "a") (BinaryOperation Subtraction (Reference "a") (IntegerLiteral 5)))) $
+    parseExpression [IDENTIFIER "a",MINUSEQUAL,INTEGERLITERAL 5]
 
 testStatementIfThen = TestCase $
     assertEqual "expect empty ifthen" [If (Reference "a") (Block [Block []]) Nothing] $
@@ -151,6 +166,10 @@ testStatementIfThen = TestCase $
 testStatementIfThenElse = TestCase $
     assertEqual "expect empty ifthen" [If (Reference "a") (Block [Block []]) (Just (Block [Block []]))] $
     parseStatement [IF,LBRACE,IDENTIFIER "a",RBRACE,LBRACKET,RBRACKET,ELSE,LBRACKET,RBRACKET]
+testStatementWhile = TestCase $
+    assertEqual "expect while" [While (Reference "a") (Block [Block []])] $
+    parseStatement [WHILE,LBRACE,IDENTIFIER "a",RBRACE,LBRACKET,RBRACKET]
+
 
 
 tests = TestList [
@@ -193,6 +212,13 @@ tests = TestList [
     testExpressionPostDecrement,
     testExpressionPreIncrement,
     testExpressionPreDecrement,
+    testExpressionAssign,
+    testExpressionTimesEqual,
+    testExpressionTimesEqual,
+    testExpressionDivideEqual,
+    testExpressionPlusEqual,
+    testExpressionMinusEqual,
     testStatementIfThen,
-    testStatementIfThenElse
+    testStatementIfThenElse,
+    testStatementWhile
     ]

src/Ast.hs

@@ -24,6 +24,10 @@ data StatementExpression
   | ConstructorCall DataType [Expression]
   | MethodCall Expression Identifier [Expression]
   | TypedStatementExpression DataType StatementExpression
+  | PostIncrement Expression
+  | PostDecrement Expression
+  | PreIncrement Expression
+  | PreDecrement Expression
   deriving (Show, Eq)
 
 data BinaryOperator
@@ -49,10 +53,6 @@ data BinaryOperator
 data UnaryOperator
   = Not
   | Minus
-  | PostIncrement
-  | PostDecrement
-  | PreIncrement
-  | PreDecrement
   deriving (Show, Eq)
 
 data Expression

src/Example.hs

@@ -101,24 +101,36 @@ exampleNameResolutionAssignment = Block [
 exampleCharIntOperation :: Expression
 exampleCharIntOperation = BinaryOperation Addition (CharacterLiteral 'a') (IntegerLiteral 1)
 
+exampleNullDeclaration :: Statement
+exampleNullDeclaration = LocalVariableDeclaration (VariableDeclaration "Person" "bob" (Just NullLiteral))
+
+exampleNullDeclarationFail :: Statement
+exampleNullDeclarationFail = LocalVariableDeclaration (VariableDeclaration "int" "a" (Just NullLiteral))
+
+exampleNullAssignment :: Statement
+exampleNullAssignment = StatementExpressionStatement (Assignment (Reference "a") NullLiteral)
+
+exampleIncrement :: Statement
+exampleIncrement = StatementExpressionStatement (PostIncrement (Reference "a"))
+
 testClasses :: [Class]
 testClasses = [
     Class "Person" [
-        MethodDeclaration "Person" "Person" [ParameterDeclaration "int" "initialAge"] 
+        MethodDeclaration "Person" "Person" [ParameterDeclaration "int" "initialAge"]
         (Block [
             Return (Just (Reference "this"))
         ]),
-        MethodDeclaration "void" "setAge" [ParameterDeclaration "int" "newAge"] 
+        MethodDeclaration "void" "setAge" [ParameterDeclaration "int" "newAge"]
         (Block [
             LocalVariableDeclaration (VariableDeclaration "int" "age" (Just (Reference "newAge")))
         ]),
-        MethodDeclaration "int" "getAge" [] 
+        MethodDeclaration "int" "getAge" []
         (Return (Just (Reference "age")))
     ] [
         VariableDeclaration "int" "age" Nothing  -- initially unassigned
     ],
     Class "Main" [
-        MethodDeclaration "int" "main" [] 
+        MethodDeclaration "int" "main" []
         (Block [
             LocalVariableDeclaration (VariableDeclaration "Person" "bob" (Just (StatementExpressionExpression (ConstructorCall "Person" [IntegerLiteral 25])))),
             StatementExpressionStatement (MethodCall (Reference "bob") "setAge" [IntegerLiteral 30]),
@@ -211,7 +223,7 @@ runTypeCheck = do
         printSuccess "Type checking of Program completed successfully"
         printResult "Typed Program:" typedProgram
         ) handleError
-    
+
     catch (do
         print "====================================================================================="
         typedAssignment <- evaluate (typeCheckStatement exampleNameResolutionAssignment [] sampleClasses)
@@ -226,3 +238,30 @@ runTypeCheck = do
         printResult "Result Char Int Operation:" evaluatedCharIntOperation
         ) handleError
 
+    catch (do
+        print "====================================================================================="
+        evaluatedNullDeclaration <- evaluate (typeCheckStatement exampleNullDeclaration [] sampleClasses)
+        printSuccess "Type checking of null declaration completed successfully"
+        printResult "Result Null Declaration:" evaluatedNullDeclaration
+        ) handleError
+
+    catch (do
+        print "====================================================================================="
+        evaluatedNullDeclarationFail <- evaluate (typeCheckStatement exampleNullDeclarationFail [] sampleClasses)
+        printSuccess "Type checking of null declaration failed"
+        printResult "Result Null Declaration:" evaluatedNullDeclarationFail
+        ) handleError
+
+    catch (do
+        print "====================================================================================="
+        evaluatedNullAssignment <- evaluate (typeCheckStatement exampleNullAssignment [("a", "Person")] sampleClasses)
+        printSuccess "Type checking of null assignment completed successfully"
+        printResult "Result Null Assignment:" evaluatedNullAssignment
+        ) handleError
+
+    catch (do
+        print "====================================================================================="
+        evaluatedIncrement <- evaluate (typeCheckStatement exampleIncrement [("a", "int")] sampleClasses)
+        printSuccess "Type checking of increment completed successfully"
+        printResult "Result Increment:" evaluatedIncrement
+        ) handleError

src/Parser/JavaParser.y

@@ -82,7 +82,7 @@ compilationunit  : typedeclarations { $1 }
 typedeclarations : typedeclaration { [$1] }
                  | typedeclarations typedeclaration { $1 ++ [$2] }
 
-name             : simplename { $1 }
+name             : simplename { Reference $1 }
                 --  | qualifiedname { }
 
 typedeclaration  : classdeclaration { $1 }
@@ -122,7 +122,7 @@ classtype        : classorinterfacetype{ }
 classbodydeclaration : classmemberdeclaration { $1 }
                  | constructordeclaration { $1 }
 
-classorinterfacetype : name { $1 }
+classorinterfacetype : simplename { $1 }
 
 classmemberdeclaration : fielddeclaration { $1 }
                  | methoddeclaration { $1 }
@@ -203,7 +203,7 @@ localvariabledeclarationstatement : localvariabledeclaration  SEMICOLON  { $1 }
 statement        : statementwithouttrailingsubstatement{ $1 }  -- statement returns a list of statements
                  | ifthenstatement { [$1] }
                  | ifthenelsestatement { [$1] }
-                --  | whilestatement { }
+                 | whilestatement { [$1] }
                                      
 
 expression       : assignmentexpression { $1 }
@@ -222,10 +222,10 @@ ifthenstatement  : IF LBRACE expression  RBRACE  statement { If $3 (Block $5) No
 
 ifthenelsestatement : IF LBRACE expression  RBRACE statementnoshortif ELSE statement { If $3 (Block $5)  (Just (Block $7)) }
 
-whilestatement   : WHILE LBRACE expression  RBRACE  statement { }
+whilestatement   : WHILE LBRACE expression  RBRACE  statement { While $3 (Block $5) }
 
 assignmentexpression : conditionalexpression { $1 }
-                --  | assignment { }
+                 | assignment { StatementExpressionExpression $1 }
 
 emptystatement         :  SEMICOLON  { Block [] }
 
@@ -241,7 +241,11 @@ statementnoshortif : statementwithouttrailingsubstatement { $1 }
 conditionalexpression : conditionalorexpression { $1 }
                 --  | conditionalorexpression QUESMARK expression  COLON  conditionalexpression { }
 
-assignment       : lefthandside assignmentoperator assignmentexpression { }
+assignment       : lefthandside assignmentoperator assignmentexpression {
+                        case $2 of
+                        Nothing -> Assignment $1 $3
+                        Just operator -> Assignment $1 (BinaryOperation operator $1 $3)
+                        }
         
 
 statementexpression : assignment { }
@@ -262,18 +266,18 @@ conditionalorexpression : conditionalandexpression { $1 }
 
 lefthandside     : name { $1 }
 
-assignmentoperator : ASSIGN{ }
+assignmentoperator : ASSIGN { Nothing }
-                --  | TIMESEQUAL { }
+                 | TIMESEQUAL { Just Multiplication }
-                --  | DIVIDEEQUAL { }
+                 | DIVIDEEQUAL { Just Division }
-                --  | MODULOEQUAL { }
+                 | MODULOEQUAL { Just Modulo }
-                --  | PLUSEQUAL { }
+                 | PLUSEQUAL { Just Addition }
-                --  | MINUSEQUAL { }
+                 | MINUSEQUAL { Just Subtraction }
                 --  | SHIFTLEFTEQUAL { }
                 --  | SIGNEDSHIFTRIGHTEQUAL { }
                 --  | UNSIGNEDSHIFTRIGHTEQUAL { }
-                --  | ANDEQUAL { }
+                 | ANDEQUAL { Just BitwiseAnd }
-                --  | XOREQUAL { }
+                 | XOREQUAL { Just BitwiseXor }
-                --  | OREQUAL{ }
+                 | OREQUAL{ Just BitwiseOr }
 
 preincrementexpression : INCREMENT unaryexpression { UnaryOperation PreIncrement $2 }
 
@@ -302,7 +306,7 @@ unaryexpression         : unaryexpressionnotplusminus { $1 }
                  | preincrementexpression { $1 }
 
 postfixexpression : primary { $1 }
-                 | name { Reference $1 }
+                 | name { $1 }
                  | postincrementexpression { $1 }
                  | postdecrementexpression{ $1 }
 

src/Typecheck.hs

@@ -25,7 +25,7 @@ typeCheckMethodDeclaration (MethodDeclaration retType name params body) classFie
         checkedBody = typeCheckStatement body initialSymtab classes
         bodyType = getTypeFromStmt checkedBody
         -- Check if the type of the body matches the declared return type
-    in if bodyType == retType || (bodyType == "void" && retType == "void")
+    in if bodyType == retType || (bodyType == "void" && retType == "void") || (bodyType == "null" && isObjectType retType)
        then MethodDeclaration retType name params checkedBody
        else error $ "Return type mismatch in method " ++ name ++ ": expected " ++ retType ++ ", found " ++ bodyType
 
@@ -89,50 +89,11 @@ typeCheckExpression (UnaryOperation op expr) symtab classes =
             else
               error "Logical NOT operation requires an operand of type boolean"
         Minus ->
-          if type' == "int"
+          if type' == "int" || type' == "char"
             then
-              TypedExpression "int" (UnaryOperation op expr')
+              TypedExpression type' (UnaryOperation op expr')
-          else if type' == "char"
-            then
-              TypedExpression "char" (UnaryOperation op expr')
             else
               error "Unary minus operation requires an operand of type int or char"
-        PostIncrement ->
-          if type' == "int"
-            then
-              TypedExpression "int" (UnaryOperation op expr')
-          else if type' == "char"
-            then
-              TypedExpression "char" (UnaryOperation op expr')
-            else
-              error "Post-increment operation requires an operand of type int or char"
-        PostDecrement ->
-          if type' == "int"
-            then
-              TypedExpression "int" (UnaryOperation op expr')
-          else if type' == "char"
-            then
-              TypedExpression "char" (UnaryOperation op expr')
-            else
-              error "Post-decrement operation requires an operand of type int or char"
-        PreIncrement ->
-          if type' == "int"
-            then
-              TypedExpression "int" (UnaryOperation op expr')
-          else if type' == "char"
-            then
-              TypedExpression "char" (UnaryOperation op expr')
-            else
-              error "Pre-increment operation requires an operand of type int or char"
-        PreDecrement ->
-          if type' == "int"
-            then
-              TypedExpression "int" (UnaryOperation op expr')
-          else if type' == "char"
-            then
-              TypedExpression "char" (UnaryOperation op expr')
-            else
-              error "Pre-decrement operation requires an operand of type int or char"
 
 typeCheckExpression (StatementExpressionExpression stmtExpr) symtab classes =
   let stmtExpr' = typeCheckStatementExpression stmtExpr symtab classes
@@ -146,11 +107,11 @@ typeCheckStatementExpression (Assignment ref expr) symtab classes =
       ref' = typeCheckExpression ref symtab classes
       type' = getTypeFromExpr expr'
       type'' = getTypeFromExpr ref'
-    in
+  in
-      if type'' == type' then
+    if type'' == type' || (type' == "null" && isObjectType type'') then
-        TypedStatementExpression type' (Assignment ref' expr')
+      TypedStatementExpression type'' (Assignment ref' expr')
-      else
+    else
-        error $ "Type mismatch in assignment to variable: expected " ++ type'' ++ ", found " ++ type'
+      error $ "Type mismatch in assignment to variable: expected " ++ type'' ++ ", found " ++ type'
 
 typeCheckStatementExpression (ConstructorCall className args) symtab classes =
   case find (\(Class name _ _) -> name == className) classes of
@@ -202,6 +163,42 @@ typeCheckStatementExpression (MethodCall expr methodName args) symtab classes =
                 Nothing -> error $ "Class for object type '" ++ objType ++ "' not found."
         _ -> error "Invalid object type for method call. Object must have a class type."
 
+typeCheckStatementExpression (PostIncrement expr) symtab classes =
+  let expr' = typeCheckExpression expr symtab classes
+      type' = getTypeFromExpr expr'
+   in if type' == "int" || type' == "char"
+        then
+          TypedStatementExpression type' (PostIncrement expr')
+        else
+          error "Post-increment operation requires an operand of type int or char"
+
+typeCheckStatementExpression (PostDecrement expr) symtab classes =
+  let expr' = typeCheckExpression expr symtab classes
+      type' = getTypeFromExpr expr'
+   in if type' == "int" || type' == "char"
+        then
+          TypedStatementExpression type' (PostDecrement expr')
+        else
+          error "Post-decrement operation requires an operand of type int or char"
+
+typeCheckStatementExpression (PreIncrement expr) symtab classes =
+  let expr' = typeCheckExpression expr symtab classes
+      type' = getTypeFromExpr expr'
+   in if type' == "int" || type' == "char"
+        then
+          TypedStatementExpression type' (PreIncrement expr')
+        else
+          error "Pre-increment operation requires an operand of type int or char"
+
+typeCheckStatementExpression (PreDecrement expr) symtab classes =
+  let expr' = typeCheckExpression expr symtab classes
+      type' = getTypeFromExpr expr'
+   in if type' == "int" || type' == "char"
+        then
+          TypedStatementExpression type' (PreDecrement expr')
+        else
+          error "Pre-decrement operation requires an operand of type int or char"
+
 -- ********************************** Type Checking: Statements **********************************
 
 typeCheckStatement :: Statement -> [(Identifier, DataType)] -> [Class] -> Statement
@@ -226,8 +223,12 @@ typeCheckStatement (LocalVariableDeclaration (VariableDeclaration dataType ident
         let checkedExpr = fmap (\expr -> typeCheckExpression expr symtab classes) maybeExpr
             exprType = fmap getTypeFromExpr checkedExpr
         in case exprType of
-            Just t | t /= dataType -> error $ "Type mismatch in declaration of '" ++ identifier ++ "': expected " ++ dataType ++ ", found " ++ t
+            Just t
-            _ -> TypedStatement dataType (LocalVariableDeclaration (VariableDeclaration dataType identifier checkedExpr))
+                | t == "null" && isObjectType dataType -> 
+                    TypedStatement dataType (LocalVariableDeclaration (VariableDeclaration dataType identifier checkedExpr))
+                | t /= dataType -> error $ "Type mismatch in declaration of '" ++ identifier ++ "': expected " ++ dataType ++ ", found " ++ t
+                | otherwise -> TypedStatement dataType (LocalVariableDeclaration (VariableDeclaration dataType identifier checkedExpr))
+            Nothing -> TypedStatement dataType (LocalVariableDeclaration (VariableDeclaration dataType identifier checkedExpr))
 
 typeCheckStatement (While cond stmt) symtab classes =
   let cond' = typeCheckExpression cond symtab classes
@@ -254,6 +255,7 @@ typeCheckStatement (Block statements) symtab classes =
                 If {} -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
                 While _ _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
                 Return _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
+                Block _ -> (accSts ++ [checkedStmt], currentSymtab, if stmtType /= "void" then types ++ [stmtType] else types)
                 _ -> (accSts ++ [checkedStmt], currentSymtab, types)
 
         -- Initial accumulator: empty statements list, initial symbol table, empty types list
@@ -278,6 +280,9 @@ typeCheckStatement (StatementExpressionStatement stmtExpr) symtab classes =
 
 -- ********************************** Type Checking: Helpers **********************************
 
+isObjectType :: DataType -> Bool
+isObjectType dt = dt /= "int" && dt /= "boolean" && dt /= "char"
+
 getTypeFromExpr :: Expression -> DataType
 getTypeFromExpr (TypedExpression t _) = t
 getTypeFromExpr _ = error "Untyped expression found where typed was expected"