Implement variable declaration

src/main/java/de/hsrm/compiler/Klang/visitors/EvalVisitor.java

@@ -101,6 +101,17 @@ public class EvalVisitor implements Visitor<Value> {
     return null;
   }
 
+  @Override
+  public Value visit(VariableDeclaration e) {
+    Value initialValue = null;
+    if (e.expression != null) {
+      initialValue = e.expression.welcome(this);
+    }
+
+    this.env.put(e.name, initialValue);
+    return null;
+  }
+
   @Override
   public Value visit(VariableAssignment e) {
     Value result = e.expression.welcome(this);

src/main/java/de/hsrm/compiler/Klang/visitors/GenASM.java

@@ -162,6 +162,18 @@ public class GenASM implements Visitor<Void> {
     throw new RuntimeException("Das machen wir mal nicht, ne?!");
   }
 
+  @Override
+  public Void visit(VariableDeclaration e) {
+    // If there is an initialization present,
+    // push it to the location of the local var
+    if (e.expression != null) {
+      e.expression.welcome(this);
+      int offset = this.env.get(e.name);
+      this.ex.write("    movq %rax, " + offset + "(%rbp)\n");
+    }
+    return null;
+  }
+
   @Override
   public Void visit(VariableAssignment e) {
     e.expression.welcome(this);

src/main/java/de/hsrm/compiler/Klang/visitors/GetVars.java

@@ -84,8 +84,13 @@ class GetVars implements Visitor<Void> {
   }
 
   @Override
-  public Void visit(VariableAssignment e) {
+  public Void visit(VariableDeclaration e) {
     vars.add(e.name);
+    return null;
+  }
+
+  @Override
+  public Void visit(VariableAssignment e) {
     e.expression.welcome(this);
     return null;
   }

src/main/java/de/hsrm/compiler/Klang/visitors/PrettyPrintVisitor.java

@@ -153,6 +153,18 @@ public class PrettyPrintVisitor implements Visitor<Void> {
         return null;
     }
 
+    @Override
+    public Void visit(VariableDeclaration e) {
+        ex.write("let " + e.name);
+
+        if (e.expression != null) {
+            ex.write(" = " + e.expression.welcome(this));
+        }
+
+        ex.write(";");
+        return null;
+    }
+
     @Override
     public Void visit(VariableAssignment e) {
         ex.write(e.name + " = ");

src/main/java/de/hsrm/compiler/Klang/visitors/Visitor.java

@@ -17,6 +17,7 @@ public interface Visitor<R> {
     R visit(NegateExpression e);
     R visit(IfStatement e);
     R visit(PrintStatement e);
+    R visit(VariableDeclaration e);
     R visit(VariableAssignment e);
     R visit(ReturnStatement e);
     R visit(Block e);