Test/JavaSources/Main.java

@@ -25,7 +25,7 @@ public class Main {
         // basic arithmetics
         assert arithmetic.basic(1, 2, 3) == 2;
         // we have boolean logic as well
-        assert arithmetic.logic(true, false, true) == true;
+        assert arithmetic.logic(false, false, true) == true;
         // multiple classes within one file work. Referencing another classes fields/methods works.
         assert multipleClasses.a.a == 42;
         // self-referencing classes work.

Test/JavaSources/TestArithmetic.java

@@ -6,6 +6,6 @@ public class TestArithmetic {
 
     public boolean logic(boolean a, boolean b, boolean c)
     {
-        return a && (c || b);
+        return !a && (c || b);
     }
 }

src/ByteCode/Assembler.hs

@@ -12,12 +12,12 @@ type Assembler a = ([ConstantInfo], [Operation], [String]) -> a -> ([ConstantInf
 
 assembleExpression :: Assembler Expression
 assembleExpression (constants, ops, lvars) (TypedExpression _ (BinaryOperation op a b))
-    | elem op [Addition, Subtraction, Multiplication, Division, Modulo, BitwiseAnd, BitwiseOr, BitwiseXor, And, Or] = let
+    | op `elem` [Addition, Subtraction, Multiplication, Division, Modulo, BitwiseAnd, BitwiseOr, BitwiseXor, And, Or] = let
             (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
             (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
         in
             (bConstants, bOps ++ [binaryOperation op], lvars)
-    | elem op [CompareEqual, CompareNotEqual, CompareLessThan, CompareLessOrEqual, CompareGreaterThan, CompareGreaterOrEqual] = let
+    | op `elem` [CompareEqual, CompareNotEqual, CompareLessThan, CompareLessOrEqual, CompareGreaterThan, CompareGreaterOrEqual] = let
             (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
             (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
             cmp_op = comparisonOperation op 9
@@ -60,7 +60,7 @@ assembleExpression (constants, ops, lvars) (TypedExpression _ (UnaryOperation Mi
 assembleExpression (constants, ops, lvars) (TypedExpression dtype (LocalVariable name))
     | name == "this" = (constants, ops ++ [Opaload 0], lvars)
     | otherwise = let
-            localIndex = findIndex ((==) name) lvars
+            localIndex = elemIndex name lvars
             isPrimitive = elem dtype ["char", "boolean", "int"]
         in case localIndex of
             Just index -> (constants, ops ++ if isPrimitive then [Opiload (fromIntegral index)] else [Opaload (fromIntegral index)], lvars)
@@ -69,7 +69,7 @@ assembleExpression (constants, ops, lvars) (TypedExpression dtype (LocalVariable
 assembleExpression (constants, ops, lvars) (TypedExpression dtype (StatementExpressionExpression stmtexp)) =
         assembleStatementExpression (constants, ops, lvars) stmtexp
 
-assembleExpression _ expr = error ("unimplemented: " ++ show expr)
+assembleExpression _ expr = error ("Unknown expression: " ++ show expr)
 
 assembleNameChain :: Assembler Expression
 assembleNameChain input (TypedExpression _ (BinaryOperation NameResolution (TypedExpression atype a) (TypedExpression _ (FieldVariable _)))) =
@@ -84,7 +84,7 @@ assembleStatementExpression
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
         (TypedExpression dtype (LocalVariable name)) -> let
-                localIndex = findIndex ((==) name) lvars
+                localIndex = elemIndex name lvars
                 (constants_a, ops_a, _) = assembleExpression (constants, ops, lvars) expr
                 isPrimitive = elem dtype ["char", "boolean", "int"]
             in case localIndex of
@@ -99,7 +99,7 @@ assembleStatementExpression
                         (constants_a, ops_a, _) = assembleExpression (constants_r, ops_r, lvars) expr
                     in
                         (constants_a, ops_a ++ [Opdup_x1, Opputfield (fromIntegral fieldIndex)], lvars)
-                something_else -> error ("expected TypedExpression, but got: " ++ show something_else)
+                something_else -> error ("Expected TypedExpression, but got: " ++ show something_else)
 
 assembleStatementExpression
     (constants, ops, lvars)
@@ -107,12 +107,12 @@ assembleStatementExpression
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
         (TypedExpression dtype (LocalVariable name)) -> let
-                localIndex = findIndex ((==) name) lvars
+                localIndex = elemIndex name lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+                expr = TypedExpression dtype (LocalVariable name)
                 (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
             in case localIndex of
                 Just index -> (exprConstants, exprOps ++ [Opsipush 1, Opiadd, Opdup, Opistore (fromIntegral index)], lvars)
-                Nothing -> error("No such local variable found in local variable pool: " ++ name)
+                Nothing -> error ("No such local variable found in local variable pool: " ++ name)
         (TypedExpression dtype (FieldVariable name)) -> let
                 owner = resolveNameChainOwner (TypedExpression dtype receiver)
             in case owner of
@@ -121,7 +121,7 @@ assembleStatementExpression
                         (constants_r, ops_r, _) = assembleNameChain (constants_f, ops, lvars) (TypedExpression dtype receiver)
                     in
                         (constants_r, ops_r ++ [Opdup, Opgetfield (fromIntegral fieldIndex), Opsipush 1, Opiadd, Opdup_x1, Opputfield (fromIntegral fieldIndex)], lvars)
-                something_else -> error ("expected TypedExpression, but got: " ++ show something_else)
+                something_else -> error ("Expected TypedExpression, but got: " ++ show something_else)
 
 assembleStatementExpression
     (constants, ops, lvars)
@@ -129,12 +129,12 @@ assembleStatementExpression
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
         (TypedExpression dtype (LocalVariable name)) -> let
-                localIndex = findIndex ((==) name) lvars
+                localIndex = elemIndex name lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+                expr = TypedExpression dtype (LocalVariable name)
                 (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
             in case localIndex of
                 Just index -> (exprConstants, exprOps ++ [Opsipush 1, Opisub, Opdup, Opistore (fromIntegral index)], lvars)
-                Nothing -> error("No such local variable found in local variable pool: " ++ name)
+                Nothing -> error ("No such local variable found in local variable pool: " ++ name)
         (TypedExpression dtype (FieldVariable name)) -> let
                 owner = resolveNameChainOwner (TypedExpression dtype receiver)
             in case owner of
@@ -143,7 +143,7 @@ assembleStatementExpression
                         (constants_r, ops_r, _) = assembleNameChain (constants_f, ops, lvars) (TypedExpression dtype receiver)
                     in
                         (constants_r, ops_r ++ [Opdup, Opgetfield (fromIntegral fieldIndex), Opsipush 1, Opisub, Opdup_x1, Opputfield (fromIntegral fieldIndex)], lvars)
-                something_else -> error ("expected TypedExpression, but got: " ++ show something_else)
+                something_else -> error ("Expected TypedExpression, but got: " ++ show something_else)
 
 assembleStatementExpression
     (constants, ops, lvars)
@@ -151,12 +151,12 @@ assembleStatementExpression
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
         (TypedExpression dtype (LocalVariable name)) -> let
-                localIndex = findIndex ((==) name) lvars
+                localIndex = elemIndex name lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+                expr = TypedExpression dtype (LocalVariable name)
                 (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
             in case localIndex of
                 Just index -> (exprConstants, exprOps ++ [Opdup, Opsipush 1, Opiadd, Opistore (fromIntegral index)], lvars)
-                Nothing -> error("No such local variable found in local variable pool: " ++ name)
+                Nothing -> error ("No such local variable found in local variable pool: " ++ name)
         (TypedExpression dtype (FieldVariable name)) -> let
                 owner = resolveNameChainOwner (TypedExpression dtype receiver)
             in case owner of
@@ -165,7 +165,7 @@ assembleStatementExpression
                         (constants_r, ops_r, _) = assembleNameChain (constants_f, ops, lvars) (TypedExpression dtype receiver)
                     in
                         (constants_r, ops_r ++ [Opdup, Opgetfield (fromIntegral fieldIndex), Opdup_x1, Opsipush 1, Opiadd, Opputfield (fromIntegral fieldIndex)], lvars)
-                something_else -> error ("expected TypedExpression, but got: " ++ show something_else)
+                something_else -> error ("Expected TypedExpression, but got: " ++ show something_else)
 
 assembleStatementExpression
     (constants, ops, lvars)
@@ -173,12 +173,12 @@ assembleStatementExpression
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
         (TypedExpression dtype (LocalVariable name)) -> let
-                localIndex = findIndex ((==) name) lvars
+                localIndex = elemIndex name lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+                expr = TypedExpression dtype (LocalVariable name)
                 (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
             in case localIndex of
                 Just index -> (exprConstants, exprOps ++ [Opdup, Opsipush 1, Opisub, Opistore (fromIntegral index)], lvars)
-                Nothing -> error("No such local variable found in local variable pool: " ++ name)
+                Nothing -> error ("No such local variable found in local variable pool: " ++ name)
         (TypedExpression dtype (FieldVariable name)) -> let
                 owner = resolveNameChainOwner (TypedExpression dtype receiver)
             in case owner of
@@ -187,7 +187,7 @@ assembleStatementExpression
                         (constants_r, ops_r, _) = assembleNameChain (constants_f, ops, lvars) (TypedExpression dtype receiver)
                     in
                         (constants_r, ops_r ++ [Opdup, Opgetfield (fromIntegral fieldIndex), Opdup_x1, Opsipush 1, Opisub, Opputfield (fromIntegral fieldIndex)], lvars)
-                something_else -> error ("expected TypedExpression, but got: " ++ show something_else)
+                something_else -> error ("Expected TypedExpression, but got: " ++ show something_else)
 
 assembleStatementExpression
     (constants, ops, lvars)
@@ -231,7 +231,7 @@ assembleStatement (constants, ops, lvars) (TypedStatement dtype (If expr if_stmt
         else_length = sum (map opcodeEncodingLength ops_elsea)
     in case dtype of
         "void" -> (constants_ifa, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq (if_length + 6)] ++ ops_ifa ++ [Opgoto (else_length + 3)] ++ ops_elsea, lvars)
-        otherwise -> (constants_ifa, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq (if_length + 3)] ++ ops_ifa ++ ops_elsea, lvars)
+        _ -> (constants_ifa, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq (if_length + 3)] ++ ops_ifa ++ ops_elsea, lvars)
 
 assembleStatement (constants, ops, lvars) (TypedStatement _ (While expr stmt)) = let
         (constants_cmp, ops_cmp, _) = assembleExpression (constants, [], lvars) expr
@@ -257,20 +257,19 @@ assembleStatement (constants, ops, lvars) (TypedStatement _ (StatementExpression
     in
         (constants_e, ops_e ++ [Oppop], lvars_e)
 
-assembleStatement _ stmt = error ("Not yet implemented: " ++ show stmt)
+assembleStatement _ stmt = error ("Unknown statement: " ++ show stmt)
 
 
 assembleMethod :: Assembler MethodDeclaration
 assembleMethod (constants, ops, lvars) (MethodDeclaration returntype name _ (TypedStatement _ (Block statements)))
     | name == "<init>"  = let
             (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
-            init_ops = [Opaload 0, Opinvokespecial 2]
         in
-            (constants_a, init_ops ++ ops_a ++ [Opreturn], lvars_a)
+            (constants_a, [Opaload 0, Opinvokespecial 2] ++ ops_a ++ [Opreturn], lvars_a)
     | otherwise = case returntype of
         "void" -> let
                 (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
             in
                 (constants_a, ops_a ++ [Opreturn], lvars_a)
-        otherwise -> foldl assembleStatement (constants, ops, lvars) statements
+        _ -> foldl assembleStatement (constants, ops, lvars) statements
 assembleMethod _ (MethodDeclaration _ _ _ stmt) = error ("Typed block expected for method body, got: " ++ show stmt)

src/ByteCode/Builder.hs

@@ -22,14 +22,14 @@ fieldBuilder (VariableDeclaration datatype name _) input = let
             ]
         field = MemberInfo {
             memberAccessFlags = accessPublic,
-            memberNameIndex = (fromIntegral (baseIndex + 2)),
+            memberNameIndex = fromIntegral (baseIndex + 2),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
+            memberDescriptorIndex = fromIntegral (baseIndex + 3),
             memberAttributes = []
             }
     in
         input {
-            constantPool = (constantPool input) ++ constants,
+            constantPool = constantPool input ++ constants,
-            fields = (fields input) ++ [field]
+            fields = fields input ++ [field]
         }
 
 
@@ -46,14 +46,14 @@ methodBuilder (MethodDeclaration returntype name parameters statement) input = l
 
         method = MemberInfo {
             memberAccessFlags = accessPublic,
-            memberNameIndex = (fromIntegral (baseIndex + 2)),
+            memberNameIndex = fromIntegral (baseIndex + 2),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
+            memberDescriptorIndex = fromIntegral (baseIndex + 3),
             memberAttributes = []
             }
     in
         input {
-            constantPool = (constantPool input) ++ constants,
+            constantPool = constantPool input ++ constants,
-            methods = (methods input) ++ [method]
+            methods = methods input ++ [method]
         }
 
 
@@ -94,11 +94,12 @@ classBuilder (Class name methods fields) _ = let
             Utf8Info "java/lang/Object",
             Utf8Info "<init>",
             Utf8Info "()V",
-            Utf8Info "Code"
+            Utf8Info "Code",
+            ClassInfo 9,
+            Utf8Info name
             ]
-        nameConstants = [ClassInfo 9, Utf8Info name]
         nakedClassFile = ClassFile {
-            constantPool = baseConstants ++ nameConstants,
+            constantPool = baseConstants,
             accessFlags = accessPublic,
             thisClass = 8,
             superClass = 1,
@@ -107,9 +108,13 @@ classBuilder (Class name methods fields) _ = let
             attributes = []
         }
 
+        -- if a class has no constructor, inject an empty one.
         methodsWithInjectedConstructor = injectDefaultConstructor methods
+        -- for every constructor, prepend all initialization assignments for fields.
         methodsWithInjectedInitializers = injectFieldInitializers name fields methodsWithInjectedConstructor
 
+        -- add fields, then method bodies to the classfile. After all referable names are known,
+        -- assemble the methods into bytecode.
         classFileWithFields = foldr fieldBuilder nakedClassFile fields
         classFileWithMethods = foldr methodBuilder classFileWithFields methodsWithInjectedInitializers
         classFileWithAssembledMethods = foldr methodAssembler classFileWithMethods methodsWithInjectedInitializers

src/ByteCode/ClassFile.hs

@@ -1,14 +1,4 @@
-module ByteCode.ClassFile(
+module ByteCode.ClassFile where
-    ConstantInfo(..),
-    Attribute(..),
-    MemberInfo(..),
-    ClassFile(..),
-    Operation(..),
-    serialize,
-    emptyClassFile,
-    opcodeEncodingLength,
-    className
-) where
 
 import Data.Word
 import Data.Int
@@ -99,10 +89,10 @@ emptyClassFile = ClassFile {
 
 className :: ClassFile -> String
 className classFile = let
-        classInfo = (constantPool classFile)!!(fromIntegral (thisClass classFile))
+        classInfo = constantPool classFile !! fromIntegral (thisClass classFile)
     in case classInfo of
         Utf8Info className -> className
-        otherwise -> error ("expected Utf8Info but got: " ++ show otherwise)
+        unexpected_element -> error ("expected Utf8Info but got: " ++ show unexpected_element)
 
 
 opcodeEncodingLength :: Operation -> Word16
@@ -201,10 +191,10 @@ instance Serializable Attribute where
     serialize (CodeAttribute { attributeMaxStack = maxStack,
                                attributeMaxLocals = maxLocals,
                                attributeCode = code }) = let
-            assembledCode = concat (map serialize code)
+            assembledCode = concatMap serialize code
         in
             unpackWord16 7                                                  -- attribute_name_index
-            ++ unpackWord32 (12 + (fromIntegral (length assembledCode)))    -- attribute_length
+            ++ unpackWord32 (12 + fromIntegral (length assembledCode))      -- attribute_length
             ++ unpackWord16 maxStack                                        -- max_stack
             ++ unpackWord16 maxLocals                                       -- max_locals
             ++ unpackWord32 (fromIntegral (length assembledCode))           -- code_length

src/ByteCode/Util.hs

@@ -10,23 +10,22 @@ import Data.Word (Word8, Word16, Word32)
 -- walks the name resolution chain. returns the innermost Just LocalVariable/FieldVariable or Nothing.
 resolveNameChain :: Expression -> Expression
 resolveNameChain (TypedExpression _ (BinaryOperation NameResolution a b)) = resolveNameChain b
-resolveNameChain (TypedExpression dtype (LocalVariable name)) = (TypedExpression dtype (LocalVariable name))
+resolveNameChain (TypedExpression dtype (LocalVariable name)) = TypedExpression dtype (LocalVariable name)
-resolveNameChain (TypedExpression dtype (FieldVariable name)) = (TypedExpression dtype (FieldVariable name))
+resolveNameChain (TypedExpression dtype (FieldVariable name)) = TypedExpression dtype (FieldVariable name)
-resolveNameChain invalidExpression = error ("expected a NameResolution or Local/Field Variable but got: " ++ show (invalidExpression))
+resolveNameChain invalidExpression = error ("expected a NameResolution or Local/Field Variable but got: " ++ show invalidExpression)
 
 -- walks the name resolution chain. returns the second-to-last item of the namechain.
 resolveNameChainOwner :: Expression -> Expression
 resolveNameChainOwner (TypedExpression _ (BinaryOperation NameResolution a (TypedExpression dtype (FieldVariable name)))) = a
 resolveNameChainOwner (TypedExpression _ (BinaryOperation NameResolution a b)) = resolveNameChain b
-resolveNameChainOwner invalidExpression = error ("expected a NameResolution or Local/Field Variable but got: " ++ show (invalidExpression))
+resolveNameChainOwner invalidExpression = error ("expected a NameResolution or Local/Field Variable but got: " ++ show invalidExpression)
-
 
 methodDescriptor :: MethodDeclaration -> String
 methodDescriptor (MethodDeclaration returntype _ parameters _) = let
         parameter_types = [datatype | ParameterDeclaration datatype _ <- parameters]
     in
         "("
-        ++ (concat (map datatypeDescriptor parameter_types))
+        ++ concatMap datatypeDescriptor parameter_types
         ++ ")"
         ++ datatypeDescriptor returntype
 
@@ -35,10 +34,12 @@ methodDescriptorFromParamlist parameters returntype = let
         parameter_types = [datatype | TypedExpression datatype _ <- parameters]
     in
         "("
-        ++ (concat (map datatypeDescriptor parameter_types))
+        ++ concatMap datatypeDescriptor parameter_types
         ++ ")"
         ++ datatypeDescriptor returntype
 
+-- recursively parses a given type signature into a list of parameter types and the method return type.
+-- As an initial parameter, you can supply ([], "void").
 parseMethodType :: ([String], String) -> String -> ([String], String)
 parseMethodType (params, returnType) ('(' : descriptor) = parseMethodType (params, returnType) descriptor
 parseMethodType (params, returnType) ('I' : descriptor) = parseMethodType (params ++ ["I"], returnType) descriptor
@@ -51,16 +52,16 @@ parseMethodType (params, returnType) ('L' : descriptor) = let
                 (typeName, semicolon : restOfDescriptor) = splitAt length descriptor
             in
                 parseMethodType (params ++ [typeName], returnType) restOfDescriptor
-        Nothing -> error $ "unterminated class type in function signature: " ++ (show descriptor)
+        Nothing -> error $ "unterminated class type in function signature: " ++ show descriptor
 parseMethodType (params, _) (')' : descriptor) = (params, descriptor)
 parseMethodType _ descriptor = error $ "expected start of type name (L, I, C, Z) but got: " ++ descriptor
 
 -- given a method index (constant pool index), 
 -- returns the full type of the method. (i.e (LSomething;II)V)
 methodTypeFromIndex :: [ConstantInfo] -> Int -> String
-methodTypeFromIndex constants index = case constants!!(fromIntegral (index - 1)) of
+methodTypeFromIndex constants index = case constants !! fromIntegral (index - 1) of
-    MethodRefInfo _ nameAndTypeIndex -> case constants!!(fromIntegral (nameAndTypeIndex - 1)) of
+    MethodRefInfo _ nameAndTypeIndex -> case constants !! fromIntegral (nameAndTypeIndex - 1) of
-        NameAndTypeInfo _ typeIndex -> case constants!!(fromIntegral (typeIndex - 1)) of
+        NameAndTypeInfo _ typeIndex -> case constants !! fromIntegral (typeIndex - 1) of
             Utf8Info typeLiteral -> typeLiteral
             unexpectedElement -> error "Expected Utf8Info but got: " ++ show unexpectedElement
         unexpectedElement -> error "Expected NameAndTypeInfo but got: " ++ show unexpectedElement
@@ -70,7 +71,7 @@ methodParametersFromIndex :: [ConstantInfo] -> Int -> ([String], String)
 methodParametersFromIndex constants index = parseMethodType ([], "V") (methodTypeFromIndex constants index)
 
 memberInfoIsMethod :: [ConstantInfo] -> MemberInfo -> Bool
-memberInfoIsMethod constants info = elem '(' (memberInfoDescriptor constants info)
+memberInfoIsMethod constants info = '(' `elem` memberInfoDescriptor constants info
 
 datatypeDescriptor :: String -> String
 datatypeDescriptor "void" = "V"
@@ -79,35 +80,24 @@ datatypeDescriptor "char" = "C"
 datatypeDescriptor "boolean" = "Z"
 datatypeDescriptor x = "L" ++ x ++ ";"
 
-
 memberInfoDescriptor :: [ConstantInfo] -> MemberInfo -> String
-memberInfoDescriptor constants MemberInfo {
+memberInfoDescriptor constants MemberInfo { memberDescriptorIndex = descriptorIndex } = let
-    memberAccessFlags = _,
+            descriptor = constants !! (fromIntegral descriptorIndex - 1)
-    memberNameIndex = _,
-    memberDescriptorIndex = descriptorIndex,
-    memberAttributes = _ } = let
-            descriptor = constants!!((fromIntegral descriptorIndex) - 1)
         in case descriptor of
             Utf8Info descriptorText -> descriptorText
-            _ -> ("Invalid Item at Constant pool index " ++ show descriptorIndex)
+            _ -> "Invalid Item at Constant pool index " ++ show descriptorIndex
-
 
 memberInfoName :: [ConstantInfo] -> MemberInfo -> String
-memberInfoName constants MemberInfo {
+memberInfoName constants MemberInfo { memberNameIndex = nameIndex } = let
-    memberAccessFlags = _,
+            name = constants !! (fromIntegral nameIndex - 1)
-    memberNameIndex = nameIndex,
-    memberDescriptorIndex = _,
-    memberAttributes = _ } = let
-            name = constants!!((fromIntegral nameIndex) - 1)
         in case name of
             Utf8Info nameText -> nameText
-            _ -> ("Invalid Item at Constant pool index " ++ show nameIndex)
+            _ -> "Invalid Item at Constant pool index " ++ show nameIndex
-
 
 returnOperation :: DataType -> Operation
 returnOperation dtype
-    | elem dtype ["int", "char", "boolean"] = Opireturn
+    | dtype `elem` ["int", "char", "boolean"] = Opireturn
-    | otherwise                             = Opareturn
+    | otherwise                               = Opareturn
 
 binaryOperation :: BinaryOperator -> Operation
 binaryOperation Addition       = Opiadd
@@ -141,50 +131,15 @@ comparisonOffset anything_else = Nothing
 isComparisonOperation :: Operation -> Bool
 isComparisonOperation op = isJust (comparisonOffset op)
 
-findFieldIndex :: [ConstantInfo] -> String -> Maybe Int
-findFieldIndex constants name = let
-        fieldRefNameInfos = [
-                -- we only skip one entry to get the name since the Java constant pool
-                -- is 1-indexed (why)
-                (index, constants!!(fromIntegral index + 1))
-                | (index, FieldRefInfo classIndex _) <- (zip [1..] constants)
-            ]
-        fieldRefNames = map (\(index, nameInfo) -> case nameInfo of
-            Utf8Info fieldName -> (index, fieldName)
-            something_else -> error ("Expected UTF8Info but got" ++ show something_else))
-                fieldRefNameInfos
-        fieldIndex = find (\(index, fieldName) -> fieldName == name) fieldRefNames
-    in case fieldIndex of
-        Just (index, _) -> Just index
-        Nothing -> Nothing
-
-findMethodRefIndex :: [ConstantInfo] -> String -> Maybe Int
-findMethodRefIndex constants name = let
-        methodRefNameInfos = [
-                -- we only skip one entry to get the name since the Java constant pool
-                -- is 1-indexed (why)
-                (index, constants!!(fromIntegral index + 1))
-                | (index, MethodRefInfo _ _) <- (zip [1..] constants)
-            ]
-        methodRefNames = map (\(index, nameInfo) -> case nameInfo of
-            Utf8Info methodName -> (index, methodName)
-            something_else -> error ("Expected UTF8Info but got " ++ show something_else))
-                methodRefNameInfos
-        methodIndex = find (\(index, methodName) -> methodName == name) methodRefNames
-    in case methodIndex of
-        Just (index, _) -> Just index
-        Nothing -> Nothing
-
-
 findMethodIndex :: ClassFile -> String -> Maybe Int
 findMethodIndex classFile name = let
         constants = constantPool classFile
     in
-        findIndex (\method -> ((memberInfoIsMethod constants method) && (memberInfoName constants method) == name)) (methods classFile)
+        findIndex (\method -> memberInfoIsMethod constants method && memberInfoName constants method == name) (methods classFile)
 
 findClassIndex :: [ConstantInfo] -> String -> Maybe Int
 findClassIndex constants name = let
-        classNameIndices = [(index, constants!!(fromIntegral nameIndex - 1)) | (index, ClassInfo nameIndex) <- (zip [1..] constants)]
+        classNameIndices = [(index, constants!!(fromIntegral nameIndex - 1)) | (index, ClassInfo nameIndex) <- zip [1..] constants]
         classNames = map (\(index, nameInfo) -> case nameInfo of
             Utf8Info className -> (index, className)
             something_else -> error ("Expected UTF8Info but got " ++ show something_else))
@@ -198,10 +153,10 @@ getKnownMembers :: [ConstantInfo] -> [(Int, (String, String, String))]
 getKnownMembers constants = let
         fieldsClassAndNT = [
                 (index, constants!!(fromIntegral classIndex - 1), constants!!(fromIntegral nameTypeIndex - 1))
-                | (index, FieldRefInfo classIndex nameTypeIndex) <- (zip [1..] constants)
+                | (index, FieldRefInfo classIndex nameTypeIndex) <- zip [1..] constants
             ] ++ [
                 (index, constants!!(fromIntegral classIndex - 1), constants!!(fromIntegral nameTypeIndex - 1))
-                | (index, MethodRefInfo classIndex nameTypeIndex) <- (zip [1..] constants)
+                | (index, MethodRefInfo classIndex nameTypeIndex) <- zip [1..] constants
             ]
 
         fieldsClassNameType = map (\(index, nameInfo, nameTypeInfo) -> case (nameInfo, nameTypeInfo) of
@@ -280,9 +235,9 @@ injectFieldInitializers classname vars pre = let
                 otherwise -> Nothing
             ) vars
     in
-        map (\(method) -> case method of
+        map (\method -> case method of
                 MethodDeclaration "void" "<init>" params (TypedStatement "void" (Block statements)) -> MethodDeclaration "void" "<init>" params (TypedStatement "void" (Block (initializers ++ statements)))
-                otherwise -> method
+                _ -> method
             ) pre
 
 -- effect of one instruction/operation on the stack
@@ -312,10 +267,10 @@ operationStackCost constants Opdup_x1        =  1
 operationStackCost constants Oppop           = -1
 operationStackCost constants (Opinvokespecial idx) = let
         (params, returnType) = methodParametersFromIndex constants (fromIntegral idx)
-    in  (length params + 1) - (fromEnum (returnType /= "V"))
+    in  (length params + 1) - fromEnum (returnType /= "V")
 operationStackCost constants (Opinvokevirtual idx) = let
         (params, returnType) = methodParametersFromIndex constants (fromIntegral idx)
-    in  (length params + 1) - (fromEnum (returnType /= "V"))
+    in  (length params + 1) - fromEnum (returnType /= "V")
 operationStackCost constants (Opgoto _)      =  0
 operationStackCost constants (Opsipush _)    =  1
 operationStackCost constants (Opldc_w _)     =  1