added constructordeclaration

Reviewed-on: #6

Test/JavaSources/Main.java

@@ -1,7 +1,7 @@
 // compile all test files using:
 // ls Test/JavaSources/*.java | grep -v ".*Main.java" | xargs -I {} cabal run compiler {}
 // compile (in project root) using:
-// javac -g:none -sourcepath Test/JavaSources/ Test/JavaSources/Main.java 
+// pushd Test/JavaSources; javac -g:none Main.java; popd
 // afterwards, run using
 // java -ea -cp Test/JavaSources/ Main
 
@@ -11,6 +11,7 @@ public class Main {
         TestEmpty empty = new TestEmpty();
         TestFields fields = new TestFields();
         TestConstructor constructor = new TestConstructor(42);
+        TestArithmetic arithmetic = new TestArithmetic();
         TestMultipleClasses multipleClasses = new TestMultipleClasses();
         TestRecursion recursion = new TestRecursion(10);
         TestMalicious malicious = new TestMalicious();
@@ -21,6 +22,10 @@ public class Main {
         assert fields.a == 0 && fields.b == 42;
         // constructor parameters override initializers
         assert constructor.a == 42;
+        // basic arithmetics
+        assert arithmetic.basic(1, 2, 3) == 2;
+        // we have boolean logic as well
+        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

@@ -0,0 +1,11 @@
+public class TestArithmetic {
+    public int basic(int a, int b, int c)
+    {
+        return a + b - c * a / b % c;
+    }
+
+    public boolean logic(boolean a, boolean b, boolean c)
+    {
+        return !a && (c || b);
+    }
+}

Test/JavaSources/TestRecursion.java

@@ -23,5 +23,12 @@ public class TestRecursion {
         {
             return fibonacci(n - 1) + this.fibonacci(n - 2);
         }
-    }    
+    }
+
+    public int ackermann(int m, int n)
+    {
+        if (m == 0) return n + 1;
+        if (n == 0) return ackermann(m - 1, 1);
+        return ackermann(m - 1, ackermann(m, n - 1));
+    }
 }

Test/TestParser.hs

@@ -238,6 +238,40 @@ testStatementPreIncrement = TestCase $
     assertEqual "expect increment" [StatementExpressionStatement $ PostIncrement $ Reference "a"] $
     parseStatement [IDENTIFIER "a",INCREMENT,SEMICOLON]
 
+testForLoop = TestCase $
+    assertEqual "expect for loop" [Block [
+        LocalVariableDeclaration (VariableDeclaration "int" "i" (Just (IntegerLiteral 0))),
+        While (BinaryOperation CompareLessThan (Reference "i") (IntegerLiteral 3)) (Block [Block [], StatementExpressionStatement (PostIncrement (Reference "i"))])
+        ]] $
+    parseStatement [FOR,LBRACE,INT,IDENTIFIER "i",ASSIGN,INTEGERLITERAL 0,SEMICOLON,IDENTIFIER "i",LESS,INTEGERLITERAL 3,SEMICOLON,IDENTIFIER "i",INCREMENT,RBRACE,LBRACKET,RBRACKET]
+testForLoopExpressionlistInInit = TestCase $
+    assertEqual "expect expressionlist in init part of for loop" [Block [
+        StatementExpressionStatement (PostIncrement (Reference "i")),
+        While (BinaryOperation CompareLessThan (Reference "i") (IntegerLiteral 3)) (Block [Block [], StatementExpressionStatement (PostIncrement (Reference "i"))])
+        ]] $
+    parseStatement [FOR,LBRACE,IDENTIFIER "i",INCREMENT,SEMICOLON,IDENTIFIER "i",LESS,INTEGERLITERAL 3,SEMICOLON,IDENTIFIER "i",INCREMENT,RBRACE,LBRACKET,RBRACKET]
+testForLoopMultipleUpdateExpressions = TestCase $
+    assertEqual "expect for loop with multiple update statements" [Block [
+        LocalVariableDeclaration (VariableDeclaration "int" "i" (Just (IntegerLiteral 0))),
+        While (BinaryOperation CompareLessThan (Reference "i") (IntegerLiteral 3)) (Block [Block [], StatementExpressionStatement (PostIncrement (Reference "i")), StatementExpressionStatement (PostIncrement (Reference "k"))])
+        ]] $
+    parseStatement [FOR,LBRACE,INT,IDENTIFIER "i",ASSIGN,INTEGERLITERAL 0,SEMICOLON,IDENTIFIER "i",LESS,INTEGERLITERAL 3,SEMICOLON,IDENTIFIER "i",INCREMENT,COMMA,IDENTIFIER "k",INCREMENT,RBRACE,LBRACKET,RBRACKET]
+testForLoopEmptyFirstPart = TestCase $
+    assertEqual "expect for loop with empty init part" [Block [
+        While (BinaryOperation CompareLessThan (Reference "i") (IntegerLiteral 3)) (Block [Block [], StatementExpressionStatement (PostIncrement (Reference "i"))])
+        ]] $
+    parseStatement [FOR,LBRACE,SEMICOLON,IDENTIFIER "i",LESS,INTEGERLITERAL 3,SEMICOLON,IDENTIFIER "i",INCREMENT,RBRACE,LBRACKET,RBRACKET]
+testForLoopEmtpySecondPart = TestCase $
+    assertEqual "expect for loop with empty expresion part" [Block [
+        While (BooleanLiteral True) (Block [Block [], StatementExpressionStatement (PostIncrement (Reference "i"))])
+        ]] $
+    parseStatement [FOR,LBRACE,SEMICOLON,SEMICOLON,IDENTIFIER "i",INCREMENT,RBRACE,LBRACKET,RBRACKET]
+testForLoopEmtpy = TestCase $
+    assertEqual "expect empty for loop" [Block [While (BooleanLiteral True) (Block [Block []])]] $
+    parseStatement [FOR,LBRACE,SEMICOLON,SEMICOLON,RBRACE,LBRACKET,RBRACKET]
+
+
+
 
 tests = TestList [
     testSingleEmptyClass,
@@ -308,5 +342,11 @@ tests = TestList [
     testStatementMethodCallNoParams,
     testStatementConstructorCall,
     testStatementConstructorCallWithArgs,
-    testStatementPreIncrement
+    testStatementPreIncrement,
+    testForLoop,
+    testForLoopExpressionlistInInit,
+    testForLoopMultipleUpdateExpressions,
+    testForLoopEmptyFirstPart,
+    testForLoopEmtpySecondPart,
+    testForLoopEmtpy
     ]

doc/bytecode.md

@@ -4,20 +4,7 @@ Die Bytecodegenerierung ist letztendlich eine zweistufige Transformation:
 
 `Getypter AST -> [ClassFile] -> [[Word8]]`
 
-Vom AST, der bereits den Typcheck durchlaufen hat, wird zunächst eine Abbildung in die einzelnen ClassFiles vorgenommen. Diese ClassFiles werden anschließend in deren Byte-Repräsentation serialisiert.
-
-## Serialisierung
-
-Damit Bytecode generiert werden kann, braucht es Strukturen, die die Daten halten, die letztendlich serialisiert werden. Die JVM erwartet den kompilierten Code in handliche Pakete verpackt. Die Struktur dieser Pakete ist [so definiert](https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html).
-
-Jede Struktur, die in dieser übergreifenden Class File vorkommt, haben wir in Haskell abgebildet. Es gibt z.B die Struktur "ClassFile", die wiederum weitere Strukturen wie z.B Informationen über Felder oder Methoden der Klasse. Alle diese Strukturen implementieren folgendes TypeClass:
-
-```
-class Serializable a where
-    serialize :: a -> [Word8]
-```
-
-Die Struktur ClassFile ruft für deren Kinder rekursiv diese `serialize` Funktion auf. Am Ende bleibt eine flache Word8-Liste übrig, die Serialisierung ist damit abgeschlossen.
+Vom AST, der bereits den Typcheck durchlaufen hat, wird zunächst eine Abbildung in die einzelnen ClassFiles vorgenommen. Diese ClassFiles werden anschließend in deren Byte-Repräsentation serialisiert. Dieser Teil der Aufgabenstellung wurde gemeinsam von Christian Brier und Matthias Raba umgesetzt.
 
 ## Codegenerierung
 
@@ -32,7 +19,6 @@ Die Idee hinter beiden ist, dass sie jeweils zwei Inputs haben, wobei der Rückg
 Der Nutzer ruft beispielsweise die Funktion `classBuilder` auf. Diese wendet nach und nach folgende Transformationen an:
 
 ```
-
         methodsWithInjectedConstructor = injectDefaultConstructor methods
         methodsWithInjectedInitializers = injectFieldInitializers name fields methodsWithInjectedConstructor
 
@@ -47,7 +33,7 @@ Zuerst wird (falls notwendig) ein leerer Defaultkonstruktor in die Classfile ein
     2. Hinzufügen aller Methoden (nur Prototypen)
     3. Hinzufügen des Bytecodes in allen Methoden
 
-Die Unterteilung von Schritt 2 und 3 ist deswegen notwendig, weil der Code einer Methode auch eine andere, erst nachher deklarierte Methode aufrufen kann. Nach Schritt 2 sind alle Methoden der Klasse bekannt. Wie beschrieben wird auch hier der Zustand über alle Faltungen mitgenommen. Jeder Schritt hat Zugriff auf alle Daten, die aus dem vorherigen Schritt bleiben. Sukkzessive wird eine korrekte ClassFile aufgebaut.
+Die Unterteilung von Schritt 2 und 3 ist deswegen notwendig, weil der Code einer Methode auch eine andere, erst nachher deklarierte Methode aufrufen kann. Nach Schritt 2 sind alle Methoden der Klasse bekannt. Wie beschrieben wird auch hier der Zustand über alle Faltungen mitgenommen. Jeder Schritt hat Zugriff auf alle Daten, die aus dem vorherigen Schritt bleiben. Sukzessive wird eine korrekte ClassFile aufgebaut.
 
 Besonders interessant ist hierbei Schritt 3. Dort wird das Verhalten jeder einzelnen Methode in Bytecode übersetzt. In diesem Schritt werden zusätzlich zu den `Buildern` noch die `Assembler` verwendet (Definition siehe oben.) Die Assembler funktionieren ähnlich wie die Builder, arbeiten allerdings nicht auf einer ClassFile, sondern auf dem Inhalt einer Methode: Sie verarbeiten jeweils ein Tupel:
 
@@ -66,4 +52,28 @@ assembleExpression (constants, ops, lvars) (TypedExpression _ NullLiteral) =
 
 Hier werden die Konstanten und lokalen Variablen des Inputs nicht berührt, dem Bytecode wird lediglich die Operation `aconst_null` hinzugefügt. Damit ist das Verhalten des gematchten Inputs - eines Nullliterals - abgebildet.
 
-Die Assembler rufen sich teilweise rekursiv selbst auf, da ja auch der AST verschachteltes Verhalten abbilden kann. Der Startpunkt für die Assembly einer Methode ist der Builder `methodAssembler`. Dieser entspricht Schritt 3 in der obigen Übersicht.
+Die Assembler rufen sich teilweise rekursiv selbst auf, da ja auch der AST verschachteltes Verhalten abbilden kann. Der Startpunkt für die Assembly einer Methode ist der Builder `methodAssembler`. Dieser entspricht Schritt 3 in der obigen Übersicht.
+
+## Serialisierung
+
+Damit Bytecode generiert werden kann, braucht es Strukturen, die die Daten halten, die letztendlich serialisiert werden. Die JVM erwartet den kompilierten Code in handliche Pakete verpackt. Die Struktur dieser Pakete ist [so definiert](https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html).
+
+Jede Struktur, die in dieser übergreifenden Class File vorkommt, haben wir in Haskell abgebildet. Es gibt z.B die Struktur "ClassFile", die wiederum weitere Strukturen wie z.B Informationen über Felder oder Methoden der Klasse beinhaltet. Alle diese Strukturen implementieren folgende TypeClass:
+
+```
+class Serializable a where
+    serialize :: a -> [Word8]
+```
+
+Hier ist ein Beispiel anhand der Serialisierung der einzelnen Operationen:
+
+```
+instance Serializable Operation where
+    serialize Opiadd                    = [0x60]
+    serialize Opisub                    = [0x64]
+    serialize Opimul                    = [0x68]
+    ...
+    serialize (Opgetfield index)        = 0xB4 : unpackWord16 index
+```
+
+Die Struktur ClassFile ruft für deren Kinder rekursiv diese `serialize` Funktion auf und konkateniert die Ergebnisse. Am Ende bleibt eine flache Word8-Liste übrig, die Serialisierung ist damit abgeschlossen. Da der Typecheck sicherstellt, dass alle referenzierten Methoden/Felder gültig sind, kann die Übersetzung der einzelnen Klassen voneinander unabhängig geschehen.

doc/features.md

@@ -0,0 +1,29 @@
+# Sprach-Features
+- Klassen
+- Felder
+- Methoden (mit Parametern)
+- Konstruktoren (mit Parametern)
+- Standardkonstruktoren
+- Lokale Variablen
+- Zuweisungen (Feld- und lokale Variablen)
+- Arithmetik (+, -, *, /, %, Klammern, Korrekte Operator Precedence)
+- Arithmetische Zuweisungen (+=, -=, *=, /=, %=, &=, |=, ^=)
+- Vergleichsoperationen (<, >, <=, >=, ==, !=)
+- Boolsche Operationen (||, &&)
+- Unäre Operationen (-, ~)
+- Binar-Operationen (&, |, ^)
+- Pre/Post-Inkrement & Dekrement
+- Kontrollflussstrukturen:
+    - If/Else
+    - While
+    - For
+    - Return (mit/ohne Rückgabewert)
+- Default-Werte für alle Klassenfelder
+- Methodenaufrufe (mit Parametern), auch über Klassengrenzen
+- Mehrere Klassen in einer Datei
+- implizites "this"
+- Beliebig verschachtelte Namensketten
+- Beliebige Deklarationsreihenfolge
+- Literale für Integer und Characters
+- Deklaration und Zuweisung in einer Anweisung
+- Beliebig verschachtelte Blöcke

doc/parser.md

@@ -0,0 +1,19 @@
+# Lexer 
+(Marvin Schlegel)
+
+Der Lexer wurde mit dem Alex tool implementiert. Dieser ist dafür zuständig den langen String in einzelne Tokens umzuwandeln. In der Alex Datei gibt es für jedes Token einen regulären Ausdruck. Bei den meisten Tokens ist das einfach das Schlüsselwort. Etwas komplexer waren Identifier, Integerliterale Strings und Chars. Für die Definition wurde sich eng an die offizielle Java Language Specification gehalten. Es ist beispielsweise auch möglich Unterstriche in Integerliterale einzubauen (Bsp.: `234_343_000`) Es sind fast alle Schlüsselwörter von Java im Lexer implementiert, auch wenn nicht alle davon vom Parser geparst werden können. Whitespace und Kommentare werden direkt ignoriert und verworfen. Für Charliterale und Integerliterale gibt es auch spezielle Fehlermeldungen. Die meisten Tokens haben nur die Information, zu welchem Keyword sie gehören. Eine Ausnahme bilden der Identifier und die Literale. Für den Identifier wird noch der Name gespeichert und für die Literale der entsprechende Wert. Mit der Funktion alexScanTokens kann dann ein beliebiger String in Tokens umgewandelt werden.
+
+Die komplexeren Tokens haben Unittests, welche mit dem Testframework HUnit geschrieben wurden. Es gibt Tests für Kommentare, Identifier, Literale und ein paar weitere Tokens.
+
+# Parser
+(Marvin Schlegel)
+
+Der Parser wurde mit dem Happy tool implementiert. Er baut aus einer Liste von Tokens einen ungetypten AST. Wir haben bereits eine Grammatik bekommen und mussten diese noch in den AST umwandeln.
+
+Um den Parser aufzubauen wurde zuerst ein Großteil der Grammatik auskommentiert und Stück für Stück wurden die Umwandlungen hinzugefügt. Immer wenn ein neues Feature umgesetzt wurde, wurde dafür ein weiterer Unit Test geschrieben. Es gibt also für jede komplexe Ableitungsregel mindestens einen Unittest.
+
+Als erstes wurden leere Methoden und Felder umgesetzt. Da in Java Methoden und Felder durcheinander vorkommen können geben die Ableitungsregeln einen Datentype namens `MethodOrFieldDeclaration` zurück. Über Pattern Matching baut die classbodydeclarations Regel dann eine Tupel mit einer Liste aus Methoden und einer aus Feldern. Über pattern matching werden diese Listen dann erweitert und in der darüberliegenden Regel schließlich extrahiert. Die Konstruktoren sind in diesem Fall auch normale Methoden mit dem Rückgabewert `void` und dem Namen `<init>`. Auf diese Weise müssen sie nicht mehr vom Typcheck oder vom Bytecode verändert werden.
+
+In Java ist es möglich mehrere Variablen in einer Zeile zu deklarieren (Bsp.: `int x, y;`). Beim Parsen ergiebt sich dann die Schwierigkeit, dass man in dem Moment, wo man die Variable parst nicht weiß welchen Datentyp diese hat. Aus diesem Grund gibt es den Datentyp Declarator, welcher nur den Identifier und eventuell eine Zuweisung enthält. In den darüberliegenden Regeln fielddeclaration und localvariabledeclaration wird dann die Typinformation hinzugefügt mithilfe der Funktion convertDeclarator.
+
+Für die Zuweisung wird auch die Kombination mit Rechenoperatoren unterstützt. Das ganze ist als syntactic sugar im Parser umgesetzt. Wenn es einen Zuweisungsoperator gibt, dann wird der Ausdruck in eine Zuweisung und Rechnung aufgeteilt. Bsp.: `x += 3;` wird umgewandelt in `x = x + 3`.

src/Ast.hs

@@ -2,12 +2,13 @@ module Ast where
 
 type CompilationUnit = [Class]
 type DataType = String
-type Identifier = String 
+type Identifier = String
 
 data ParameterDeclaration = ParameterDeclaration DataType Identifier deriving (Show, Eq)
 data VariableDeclaration = VariableDeclaration DataType Identifier (Maybe Expression) deriving (Show, Eq)
 data Class = Class DataType [MethodDeclaration] [VariableDeclaration] deriving (Show, Eq)
 data MethodDeclaration = MethodDeclaration DataType Identifier [ParameterDeclaration] Statement deriving (Show, Eq)
+data ConstructorDeclaration = ConstructorDeclaration Identifier [ParameterDeclaration] Statement deriving (Show, Eq)
 
 data Statement
   = If Expression Statement (Maybe Statement)

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
@@ -99,20 +99,20 @@ 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)
     (TypedStatementExpression _ (PreIncrement (TypedExpression dtype receiver))) = let
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
-        (TypedExpression dtype (LocalVariable name)) -> let 
-                localIndex = findIndex ((==) name) lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+        (TypedExpression dtype (LocalVariable name)) -> let
+                localIndex = elemIndex name lvars
+                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
@@ -121,20 +121,20 @@ 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)
     (TypedStatementExpression _ (PreDecrement (TypedExpression dtype receiver))) = let
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
-        (TypedExpression dtype (LocalVariable name)) -> let 
-                localIndex = findIndex ((==) name) lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+        (TypedExpression dtype (LocalVariable name)) -> let
+                localIndex = elemIndex name lvars
+                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
@@ -143,20 +143,20 @@ 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)
     (TypedStatementExpression _ (PostIncrement (TypedExpression dtype receiver))) = let
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
-        (TypedExpression dtype (LocalVariable name)) -> let 
-                localIndex = findIndex ((==) name) lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+        (TypedExpression dtype (LocalVariable name)) -> let
+                localIndex = elemIndex name lvars
+                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
@@ -165,20 +165,20 @@ 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)
     (TypedStatementExpression _ (PostDecrement (TypedExpression dtype receiver))) = let
         target = resolveNameChain (TypedExpression dtype receiver)
     in case target of
-        (TypedExpression dtype (LocalVariable name)) -> let 
-                localIndex = findIndex ((==) name) lvars
-                expr = (TypedExpression dtype (LocalVariable name))
+        (TypedExpression dtype (LocalVariable name)) -> let
+                localIndex = elemIndex name lvars
+                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
-assembleMethod _ (MethodDeclaration _ _ _ stmt) = error ("Typed block expected for method body, got: " ++ show stmt) 
+        _ -> 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)),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
+            memberNameIndex = fromIntegral (baseIndex + 2),
+            memberDescriptorIndex = fromIntegral (baseIndex + 3),
             memberAttributes = []
             }
     in
         input {
-            constantPool = (constantPool input) ++ constants,
-            fields = (fields input) ++ [field]
+            constantPool = constantPool input ++ constants,
+            fields = fields input ++ [field]
         }
 
 
@@ -46,16 +46,15 @@ methodBuilder (MethodDeclaration returntype name parameters statement) input = l
 
         method = MemberInfo {
             memberAccessFlags = accessPublic,
-            memberNameIndex = (fromIntegral (baseIndex + 2)),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
+            memberNameIndex = fromIntegral (baseIndex + 2),
+            memberDescriptorIndex = fromIntegral (baseIndex + 3),
             memberAttributes = []
             }
-    in 
+    in
         input {
-            constantPool = (constantPool input) ++ constants,
-            methods = (methods input) ++ [method]
+            constantPool = constantPool input ++ constants,
+            methods = methods input ++ [method]
         }
-        
 
 
 methodAssembler :: ClassFileBuilder MethodDeclaration
@@ -66,21 +65,22 @@ methodAssembler (MethodDeclaration returntype name parameters statement) input =
         Just index -> let
                 declaration = MethodDeclaration returntype name parameters statement
                 paramNames = "this" : [name | ParameterDeclaration _ name <- parameters]
-            in case (splitAt index (methods input)) of
+            in case splitAt index (methods input) of
                 (pre, []) -> input
                 (pre, method : post) -> let
-                        (_, bytecode, _) = assembleMethod (constantPool input, [], paramNames) declaration
+                        (constants, bytecode, aParamNames) = assembleMethod (constantPool input, [], paramNames) declaration
                         assembledMethod = method {
                             memberAttributes = [
                                 CodeAttribute {
-                                    attributeMaxStack = 420,
-                                    attributeMaxLocals = 420,
+                                    attributeMaxStack = fromIntegral $ maxStackDepth constants bytecode,
+                                    attributeMaxLocals = fromIntegral $ length aParamNames,
                                     attributeCode = bytecode
                                 }
                             ]
                         }
                     in
                         input {
+                            constantPool = constants,
                             methods = pre ++ (assembledMethod : post)
                         }
 
@@ -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(
-    ConstantInfo(..),
-    Attribute(..),
-    MemberInfo(..),
-    ClassFile(..),
-    Operation(..),
-    serialize,
-    emptyClassFile,
-    opcodeEncodingLength,
-    className
-) where
+module ByteCode.ClassFile where
 
 import Data.Word
 import Data.Int
@@ -99,11 +89,11 @@ 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
 opcodeEncodingLength Opiadd                 = 1
@@ -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

@@ -4,29 +4,28 @@ import Data.Int
 import Ast
 import ByteCode.ClassFile
 import Data.List
-import Data.Maybe (mapMaybe)
+import Data.Maybe (mapMaybe, isJust)
 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 (FieldVariable name)) = (TypedExpression dtype (FieldVariable name))
-resolveNameChain invalidExpression = error ("expected a NameResolution or Local/Field Variable but got: " ++ show(invalidExpression))
+resolveNameChain (TypedExpression dtype (LocalVariable name)) = TypedExpression dtype (LocalVariable name)
+resolveNameChain (TypedExpression dtype (FieldVariable name)) = TypedExpression dtype (FieldVariable name)
+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
 
@@ -35,50 +34,70 @@ methodDescriptorFromParamlist parameters returntype = let
         parameter_types = [datatype | TypedExpression datatype _ <- parameters]
     in
         "("
-        ++ (concat (map datatypeDescriptor parameter_types))
+        ++ concatMap datatypeDescriptor parameter_types
         ++ ")"
         ++ datatypeDescriptor returntype
 
-memberInfoIsMethod :: [ConstantInfo] -> MemberInfo -> Bool
-memberInfoIsMethod constants info = elem '(' (memberInfoDescriptor constants info)
+-- 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
+parseMethodType (params, returnType) ('C' : descriptor) = parseMethodType (params ++ ["C"], returnType) descriptor
+parseMethodType (params, returnType) ('Z' : descriptor) = parseMethodType (params ++ ["Z"], returnType) descriptor
+parseMethodType (params, returnType) ('L' : descriptor) = let
+        typeLength = elemIndex ';' descriptor
+    in case typeLength of
+        Just length -> let
+                (typeName, semicolon : restOfDescriptor) = splitAt length descriptor
+            in
+                parseMethodType (params ++ [typeName], returnType) restOfDescriptor
+        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
+    MethodRefInfo _ nameAndTypeIndex -> case constants !! fromIntegral (nameAndTypeIndex - 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
+    unexpectedElement -> error "Expected MethodRefInfo but got: " ++ show unexpectedElement
+
+methodParametersFromIndex :: [ConstantInfo] -> Int -> ([String], String)
+methodParametersFromIndex constants index = parseMethodType ([], "V") (methodTypeFromIndex constants index)
+
+memberInfoIsMethod :: [ConstantInfo] -> MemberInfo -> Bool
+memberInfoIsMethod constants info = '(' `elem` memberInfoDescriptor constants info
 
 datatypeDescriptor :: String -> String
 datatypeDescriptor "void" = "V"
 datatypeDescriptor "int" = "I"
 datatypeDescriptor "char" = "C"
-datatypeDescriptor "boolean" = "B"
+datatypeDescriptor "boolean" = "Z"
 datatypeDescriptor x = "L" ++ x ++ ";"
 
-
 memberInfoDescriptor :: [ConstantInfo] -> MemberInfo -> String
-memberInfoDescriptor constants MemberInfo {
-    memberAccessFlags = _,
-    memberNameIndex = _,
-    memberDescriptorIndex = descriptorIndex,
-    memberAttributes = _ } = let
-            descriptor = constants!!((fromIntegral descriptorIndex) - 1)
+memberInfoDescriptor constants MemberInfo { memberDescriptorIndex = descriptorIndex } = 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 {
-    memberAccessFlags = _,
-    memberNameIndex = nameIndex,
-    memberDescriptorIndex = _,
-    memberAttributes = _ } = let
-            name = constants!!((fromIntegral nameIndex) - 1)
+memberInfoName constants MemberInfo { memberNameIndex = nameIndex } = 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
-    | otherwise                             = Opareturn
+    | dtype `elem` ["int", "char", "boolean"] = Opireturn
+    | otherwise                               = Opareturn
 
 binaryOperation :: BinaryOperator -> Operation
 binaryOperation Addition       = Opiadd
@@ -100,53 +119,30 @@ comparisonOperation CompareLessOrEqual    branchLocation = Opif_icmple branchLoc
 comparisonOperation CompareGreaterThan    branchLocation = Opif_icmpgt branchLocation
 comparisonOperation CompareGreaterOrEqual branchLocation = Opif_icmpge branchLocation
 
-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
+comparisonOffset :: Operation -> Maybe Int
+comparisonOffset (Opif_icmpeq offset) = Just $ fromIntegral offset
+comparisonOffset (Opif_icmpne offset) = Just $ fromIntegral offset
+comparisonOffset (Opif_icmplt offset) = Just $ fromIntegral offset
+comparisonOffset (Opif_icmple offset) = Just $ fromIntegral offset
+comparisonOffset (Opif_icmpgt offset) = Just $ fromIntegral offset
+comparisonOffset (Opif_icmpge offset) = Just $ fromIntegral offset
+comparisonOffset anything_else = Nothing
 
+isComparisonOperation :: Operation -> Bool
+isComparisonOperation op = isJust (comparisonOffset op)
 
 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))
+            something_else -> error ("Expected UTF8Info but got " ++ show something_else))
                 classNameIndices
         desiredClassIndex = find (\(index, className) -> className == name) classNames
     in case desiredClassIndex of
@@ -157,12 +153,12 @@ 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
             (ClassInfo nameIndex, NameAndTypeInfo fnameIndex ftypeIndex) -> (index, (constants!!(fromIntegral nameIndex - 1), constants!!(fromIntegral fnameIndex - 1), constants!!(fromIntegral ftypeIndex - 1)))
             something_else -> error ("Expected Class and NameType info, but got: " ++ show nameInfo ++ " and " ++ show nameTypeInfo))
@@ -170,8 +166,8 @@ getKnownMembers constants = let
 
         fieldsResolved = map (\(index, (nameInfo, fnameInfo, ftypeInfo)) -> case (nameInfo, fnameInfo, ftypeInfo) of
             (Utf8Info cname, Utf8Info fname, Utf8Info ftype) -> (index, (cname, fname, ftype))
-            something_else -> error("Expected UTF8Infos but got " ++ show something_else))
-                fieldsClassNameType    
+            something_else -> error ("Expected UTF8Infos but got " ++ show something_else))
+                fieldsClassNameType
     in
         fieldsResolved
 
@@ -179,7 +175,7 @@ getKnownMembers constants = let
 getClassIndex :: [ConstantInfo] -> String -> ([ConstantInfo], Int)
 getClassIndex constants name = case findClassIndex constants name of
     Just index -> (constants, index)
-    Nothing -> (constants ++ [ClassInfo (fromIntegral (length constants)), Utf8Info name], fromIntegral (length constants))
+    Nothing -> (constants ++ [ClassInfo (fromIntegral (length constants) + 2), Utf8Info name], fromIntegral (length constants) + 1)
 
 -- get the index for a field within a class, creating it if it does not exist.
 getFieldIndex :: [ConstantInfo] -> (String, String, String) -> ([ConstantInfo], Int)
@@ -223,7 +219,7 @@ injectDefaultConstructor pre
     | otherwise = pre ++ [MethodDeclaration "void" "<init>" [] (TypedStatement "void" (Block []))]
 
 injectFieldInitializers :: String -> [VariableDeclaration] -> [MethodDeclaration] -> [MethodDeclaration]
-injectFieldInitializers classname vars pre = let 
+injectFieldInitializers classname vars pre = let
         initializers = mapMaybe (\(variable) -> case variable of
                 VariableDeclaration dtype name (Just initializer) -> Just (
                         TypedStatement dtype (
@@ -239,7 +235,58 @@ 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
-            ) pre
+                _ -> method
+            ) pre
+
+-- effect of one instruction/operation on the stack
+operationStackCost :: [ConstantInfo] -> Operation -> Int
+operationStackCost constants Opiadd          = -1
+operationStackCost constants Opisub          = -1
+operationStackCost constants Opimul          = -1
+operationStackCost constants Opidiv          = -1
+operationStackCost constants Opirem          = -1
+operationStackCost constants Opiand          = -1
+operationStackCost constants Opior           = -1
+operationStackCost constants Opixor          = -1
+operationStackCost constants Opineg          =  0
+operationStackCost constants Opdup           =  1
+operationStackCost constants (Opnew _)       =  1
+operationStackCost constants (Opif_icmplt _) = -2
+operationStackCost constants (Opif_icmple _) = -2
+operationStackCost constants (Opif_icmpgt _) = -2
+operationStackCost constants (Opif_icmpge _) = -2
+operationStackCost constants (Opif_icmpeq _) = -2
+operationStackCost constants (Opif_icmpne _) = -2
+operationStackCost constants Opaconst_null   =  1
+operationStackCost constants Opreturn        =  0
+operationStackCost constants Opireturn       = -1
+operationStackCost constants Opareturn       = -1
+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")
+operationStackCost constants (Opinvokevirtual idx) = let
+        (params, returnType) = methodParametersFromIndex constants (fromIntegral idx)
+    in  (length params + 1) - fromEnum (returnType /= "V")
+operationStackCost constants (Opgoto _)      =  0
+operationStackCost constants (Opsipush _)    =  1
+operationStackCost constants (Opldc_w _)     =  1
+operationStackCost constants (Opaload _)     =  1
+operationStackCost constants (Opiload _)     =  1
+operationStackCost constants (Opastore _)    = -1
+operationStackCost constants (Opistore _)    = -1
+operationStackCost constants (Opputfield _)  = -2
+operationStackCost constants (Opgetfield _)  = -1
+
+simulateStackOperation :: [ConstantInfo] -> Operation -> (Int, Int) -> (Int, Int)
+simulateStackOperation constants op (cd, md) = let
+        depth = cd + operationStackCost constants op
+    in if depth < 0
+        then error ("Consuming value off of empty stack: " ++ show op)
+        else (depth, max depth md)
+
+maxStackDepth :: [ConstantInfo] -> [Operation] -> Int
+maxStackDepth constants ops = snd $ foldr (simulateStackOperation constants) (0, 0) (reverse ops)

src/Main.hs

@@ -1,6 +1,5 @@
 module Main where
 
-import Example
 import Typecheck
 import Parser.Lexer (alexScanTokens)
 import Parser.JavaParser
@@ -14,20 +13,20 @@ main = do
     args <- getArgs
     let filename = if null args
                    then error "Missing filename, I need to know what to compile"
-                   else args!!0
+                   else head args
     let outputDirectory = takeDirectory filename
     print ("Compiling " ++ filename)
     file <- readFile filename
 
     let untypedAST = parse $ alexScanTokens file
-    let typedAST = (typeCheckCompilationUnit untypedAST)
-    let assembledClasses = map (\(typedClass) -> classBuilder typedClass emptyClassFile) typedAST
+    let typedAST = typeCheckCompilationUnit untypedAST
+    let assembledClasses = map (`classBuilder` emptyClassFile) typedAST
 
-    mapM_ (\(classFile) -> let
+    mapM_ (\classFile -> let
             fileContent = pack (serialize classFile)
-            fileName = outputDirectory ++ "/" ++ (className classFile) ++ ".class"
+            fileName = outputDirectory ++ "/" ++ className classFile ++ ".class"
         in Data.ByteString.writeFile fileName fileContent
-        ) assembledClasses
+            ) assembledClasses
+
 
 
-    

src/Parser/JavaParser.y

@@ -75,6 +75,7 @@ import Parser.Lexer
         OREQUAL { OREQUAL }
         COLON { COLON }
         LESS { LESS }
+        FOR { FOR }
 %%
 
 compilationunit  : typedeclarations { $1 }
@@ -204,6 +205,7 @@ statement        : statementwithouttrailingsubstatement{ $1 }  -- statement retu
                  | ifthenstatement { [$1] }
                  | ifthenelsestatement { [$1] }
                  | whilestatement { [$1] }
+                 | forstatement { [$1] }
                                      
 
 expression       : assignmentexpression { $1 }
@@ -224,6 +226,21 @@ ifthenelsestatement : IF LBRACE expression  RBRACE statementnoshortif ELSE state
 
 whilestatement   : WHILE LBRACE expression  RBRACE  statement { While $3 (Block $5) }
 
+forstatement : FOR LBRACE forinit optionalexpression forupdate statement { Block ($3 ++ [While ($4) (Block ($6 ++ $5))]) }
+
+forinit         : statementexpressionlist SEMICOLON { $1 }
+                | localvariabledeclaration SEMICOLON { $1 }
+                | SEMICOLON { [] }
+
+optionalexpression : expression SEMICOLON { $1 }
+                   | SEMICOLON { BooleanLiteral True }
+
+forupdate       : statementexpressionlist RBRACE { $1 }
+                | RBRACE { [] }
+
+statementexpressionlist : statementexpression { [StatementExpressionStatement $1] }
+                        | statementexpressionlist COMMA statementexpression { $1 ++ [StatementExpressionStatement $3] }
+
 assignmentexpression : conditionalexpression { $1 }
                  | assignment { StatementExpressionExpression $1 }