diff --git a/.gitignore b/.gitignore
index 3092112..2329c99 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,5 @@
 *.user
 /vs/*/*
 /bin/slime
+*.psess
+*.vspx
diff --git a/src/built_ins.c b/src/built_ins.c
index bd1c660..259eba0 100644
--- a/src/built_ins.c
+++ b/src/built_ins.c
@@ -39,84 +39,84 @@ bool ast_node_equal(Ast_Node* n1, Ast_Node* n2) {
     return false;
 }
 
-Ast_Node* built_in_equals(Parsed_Arguments* arguments) {
-    for (int i = 0; i < arguments->positional_arguments->next_index-1; ++i) {
-        if (!ast_node_equal(
-                arguments->positional_arguments->data[i],
-                arguments->positional_arguments->data[i+1]))
+Ast_Node* built_in_equals(Ast_Node* operands) {
+    if (operands->type == Ast_Node_Type_Nil)
+        return create_ast_node_number(1);
+
+    Ast_Node* first = operands->value.pair->first;
+
+    while (operands->type == Ast_Node_Type_Pair) {
+        if (!ast_node_equal(operands->value.pair->first, first))
             return create_ast_node_nil();
+        operands = operands->value.pair->rest;
     }
+
     return create_ast_node_number(1);
 }
 
-Ast_Node* built_in_add(Parsed_Arguments* arguments) {
+Ast_Node* built_in_add(Ast_Node* operands) {
     double sum = 0;
-    for (int i = 0; i < arguments->positional_arguments->next_index; ++i) {
+    while (operands->type == Ast_Node_Type_Pair) {
         try {
-            assert_type(arguments->positional_arguments->data[i], Ast_Node_Type_Number);
+            assert_type(operands->value.pair->first, Ast_Node_Type_Number);
         }
-        sum += arguments->positional_arguments->data[i]->value.number->value;
+        sum += operands->value.pair->first->value.number->value;
+        operands = operands->value.pair->rest;
     }
 
     return create_ast_node_number(sum);
 }
 
-Ast_Node* built_in_substract(Parsed_Arguments* arguments) {
-    if (arguments->positional_arguments->next_index == 0)
-        return create_ast_node_number(0);
-
+Ast_Node* built_in_substract(Ast_Node* operands) {
     try {
-        assert_type(*arguments->positional_arguments->data, Ast_Node_Type_Number);
+        assert_type(operands->value.pair->first, Ast_Node_Type_Number);
     }
+    double difference = operands->value.pair->first->value.number->value;
 
-    if (arguments->positional_arguments->next_index == 1) {
-        return create_ast_node_number(-(*arguments->positional_arguments->data)->value.number->value);
-    }
-
-    // okay we have at least 2 arguments
-    double difference = (*arguments->positional_arguments->data)->value.number->value;
-    for (int i = 1; i < arguments->positional_arguments->next_index; ++i) {
+    operands = operands->value.pair->rest;
+    while (operands->type == Ast_Node_Type_Pair) {
         try {
-            assert_type(arguments->positional_arguments->data[i], Ast_Node_Type_Number);
+            assert_type(operands->value.pair->first, Ast_Node_Type_Number);
         }
-        difference -= arguments->positional_arguments->data[i]->value.number->value;
-    }
 
+        difference -= operands->value.pair->first->value.number->value;
+        operands = operands->value.pair->rest;
+    }
     return create_ast_node_number(difference);
 }
 
-Ast_Node* built_in_multiply(Parsed_Arguments* arguments) {
-    double product = 1;
-    for (int i = 0; i < arguments->positional_arguments->next_index; ++i) {
+Ast_Node* built_in_multiply(Ast_Node* operands) {
+    try {
+        assert_type(operands->value.pair->first, Ast_Node_Type_Number);
+    }
+    double product = operands->value.pair->first->value.number->value;
+
+    operands = operands->value.pair->rest;
+    while (operands->type == Ast_Node_Type_Pair) {
         try {
-            assert_type(arguments->positional_arguments->data[i], Ast_Node_Type_Number);
+            assert_type(operands->value.pair->first, Ast_Node_Type_Number);
         }
-        product *= arguments->positional_arguments->data[i]->value.number->value;
-    }
 
+        product *= operands->value.pair->first->value.number->value;
+        operands = operands->value.pair->rest;
+    }
     return create_ast_node_number(product);
 }
 
-Ast_Node* built_in_divide(Parsed_Arguments* arguments) {
-    if (arguments->positional_arguments->next_index == 0)
-        return create_ast_node_number(1);
-
+Ast_Node* built_in_divide(Ast_Node* operands) {
     try {
-        assert_type(*arguments->positional_arguments->data, Ast_Node_Type_Number);
+        assert_type(operands->value.pair->first, Ast_Node_Type_Number);
     }
+    double quotient = operands->value.pair->first->value.number->value;
 
-    if (arguments->positional_arguments->next_index == 1) {
-        return create_ast_node_number((*arguments->positional_arguments->data)->value.number->value);
-    }
-
-    // okay we have at least 2 arguments
-    double difference = (*arguments->positional_arguments->data)->value.number->value;
-    for (int i = 1; i < arguments->positional_arguments->next_index; ++i) {
+    operands = operands->value.pair->rest;
+    while (operands->type == Ast_Node_Type_Pair) {
         try {
-            assert_type(arguments->positional_arguments->data[i], Ast_Node_Type_Number);
+            assert_type(operands->value.pair->first, Ast_Node_Type_Number);
         }
-        difference /= arguments->positional_arguments->data[i]->value.number->value;
-    }
 
-    return create_ast_node_number(difference);
+        quotient /= operands->value.pair->first->value.number->value;
+        operands = operands->value.pair->rest;
+    }
+    return create_ast_node_number(quotient);
 }
diff --git a/src/env.c b/src/env.c
index 1cd8794..03a3ee6 100644
--- a/src/env.c
+++ b/src/env.c
@@ -10,12 +10,13 @@ struct Environment {
 
 typedef struct Environment Environment;
 
-Environment* create_empty_environment() {
+
+Environment* create_child_environment(Environment* parent) {
     Environment* env = new(Environment);
 
     int start_capacity = 16;
 
-    env->parent     = nullptr;
+    env->parent     = parent;
     env->capacity   = start_capacity;
     env->next_index = 0;
     env->keys       =    (char**)malloc(start_capacity * sizeof(char*));
@@ -24,6 +25,10 @@ Environment* create_empty_environment() {
     return env;
 }
 
+Environment* create_empty_environment() {
+    return create_child_environment(nullptr);
+}
+
 void define_symbol(Ast_Node* symbol, Ast_Node* value, Environment* env) {
     // NOTE(Felix): right now we are simmply adding the symol at the
     // back of the list without checking if it already exists but are
diff --git a/src/eval.c b/src/eval.c
index e483d0b..023ce6f 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1,10 +1,33 @@
+Ast_Node* eval_expr(Ast_Node* node, Environment* env);
+
+Ast_Node* apply_arguments_to_function(Ast_Node* arguments, Function* function, Environment* parent) {
+    Environment* new_env = create_child_environment(parent);
+
+    // positional arguments
+    for (int i = 0; i < function->positional_arguments->next_index; ++i) {
+        if (arguments->type == Ast_Node_Type_Pair) {
+            define_symbol(
+                create_ast_node_symbol(function->positional_arguments->identifiers[i]),
+                arguments->value.pair->first, new_env);
+        } else {
+            // not enough arguments given
+            create_error(Error_Type_Ill_Formed_Arguments, arguments);
+            return nullptr;
+        }
+        arguments = arguments->value.pair->rest;
+    }
 
-Ast_Node* apply_arguments_to_function (Ast_Node* arguments, Ast_Node* function) {
-    printf("calling function, yey\n");
+    Ast_Node* result;
 
-    return create_ast_node_nil();
+    try {
+        result = eval_expr(function->body, new_env);
+    }
+
+    return result;
 }
 
+/* (define type (lambda (e) (if (and (= (old-type e) :pair) (= (first e) :my-type)) :my-type (old-type e)))) */
+
 /**
    This parses the argument specification of funcitons into their
    Function struct. It dois this by allocating new
@@ -189,59 +212,8 @@ Ast_Node* copy_list(Ast_Node* node) {
     return result;
 }
 
-Ast_Node* eval_expr(Ast_Node* node, Environment* env);
 bool is_truthy (Ast_Node* expression, Environment* env);
 
-Parsed_Arguments* eval_and_parse_arguments(Ast_Node* arguments, Environment* env) {
-    // TODO(Felix): if arguments is nil then maybe return a constant
-    // Parsed_Arguments_nil?
-
-
-    typedef enum {
-        Expecting_Anything,
-        Expecting_Keyword_Key,
-        Expecting_Keyword_Value
-    } Parse_State;
-
-    Parse_State parse_state = Expecting_Anything;
-
-    Parsed_Arguments* result = new(Parsed_Arguments);
-    result->positional_arguments = create_Ast_Node_Array_List(16);
-    result->keyword_keys         = create_Ast_Node_Array_List(16);
-    result->keyword_values       = create_Ast_Node_Array_List(16);
-
-    Ast_Node* current_head = copy_list(arguments);
-    Ast_Node* current_evaluated_head;
-    while (current_head->type == Ast_Node_Type_Pair) {
-        try {
-            current_evaluated_head = eval_expr(current_head->value.pair->first, env);
-        }
-        if (current_evaluated_head->type == Ast_Node_Type_Keyword) {
-            if (parse_state == Expecting_Anything || Expecting_Keyword_Key) {
-                append_to_Ast_Node_Array_List(result->keyword_keys, current_evaluated_head);
-                parse_state = Expecting_Keyword_Value;
-            } else {
-                create_error(Error_Type_Ill_Formed_Arguments, arguments);
-                return nullptr;
-            }
-        } else {
-            if (parse_state == Expecting_Anything)
-                append_to_Ast_Node_Array_List(result->positional_arguments, current_evaluated_head);
-            else if (parse_state == Expecting_Keyword_Value) {
-                append_to_Ast_Node_Array_List(result->keyword_values, current_evaluated_head);
-                parse_state = Expecting_Keyword_Key;
-            }
-            else {
-                create_error(Error_Type_Ill_Formed_Arguments, arguments);
-                return nullptr;
-            }
-        }
-        current_head = current_head->value.pair->rest;
-    }
-
-    return result;
-}
-
 Ast_Node* extract_keyword_value(char* keyword, Parsed_Arguments* args) {
     // NOTE(Felix): This will be a hashmap lookup later
     for (int i = 0; i < args->keyword_keys->next_index; ++i) {
@@ -257,16 +229,27 @@ Ast_Node* eval_arguments(Ast_Node* arguments, Environment* env, int *out_argumen
         return arguments;
     }
 
-    // NOTE(Felix): Instead of copying and then mutating it, we could
-    // just build the resulting list on the fly
-    Ast_Node* evaluated_arguments = copy_list(arguments);
-    Ast_Node* current_head = evaluated_arguments;
+    Ast_Node* evaluated_arguments = create_ast_node_pair(nullptr, nullptr);
+    Ast_Node* evaluated_arguments_head = evaluated_arguments;
+    Ast_Node* current_head = arguments;
     while (current_head->type == Ast_Node_Type_Pair) {
         try {
-            current_head->value.pair->first =
+            evaluated_arguments_head->value.pair->first =
                 eval_expr(current_head->value.pair->first, env);
         }
         current_head = current_head->value.pair->rest;
+
+        if (current_head->type == Ast_Node_Type_Pair) {
+            evaluated_arguments_head->value.pair->rest = create_ast_node_pair(nullptr, nullptr);
+            evaluated_arguments_head = evaluated_arguments_head->value.pair->rest;
+        }
+        else if (current_head->type == Ast_Node_Type_Nil) {
+            evaluated_arguments_head->value.pair->rest = current_head;
+        }
+        else {
+            create_error(Error_Type_Ill_Formed_Arguments, arguments);
+            return nullptr;
+        }
         ++(*out_arguments_length);
     }
     return evaluated_arguments;
@@ -298,8 +281,12 @@ Ast_Node* eval_expr(Ast_Node* node, Environment* env) {
         return node;
     case Ast_Node_Type_Pair: {
         Ast_Node* operator;
-        try {
-           operator = eval_expr(node->value.pair->first, env);
+        if (node->value.pair->first->type != Ast_Node_Type_Built_In_Function) {
+            try {
+                operator = eval_expr(node->value.pair->first, env);
+            }
+        } else {
+                operator = node->value.pair->first;
         }
 
         Ast_Node* arguments = node->value.pair->rest;
@@ -458,27 +445,25 @@ Ast_Node* eval_expr(Ast_Node* node, Environment* env) {
             // to evaluate the arguments; eval_arguments will also tell
             // us the arguments_length.
             Ast_Node* evaluated_arguments;
-            Parsed_Arguments* evaluated_and_parsed_arguments;
             try {
                 evaluated_arguments = eval_arguments(arguments, env, &arguments_length);
-                evaluated_and_parsed_arguments = eval_and_parse_arguments(arguments, env);
             }
 
             switch (operator->value.built_in_function->type) {
             case Built_In_Addition: {
-                return built_in_add(evaluated_and_parsed_arguments);
+                return built_in_add(evaluated_arguments);
             }
             case Built_In_Subtraction: {
-                return built_in_substract(evaluated_and_parsed_arguments);
+                return built_in_substract(evaluated_arguments);
             }
             case Built_In_Multiplication: {
-                return built_in_multiply(evaluated_and_parsed_arguments);
+                return built_in_multiply(evaluated_arguments);
             }
             case Built_In_Division: {
-                return built_in_divide(evaluated_and_parsed_arguments);
+                return built_in_divide(evaluated_arguments);
             }
             case Built_In_Equal: {
-                return built_in_equals(evaluated_and_parsed_arguments);
+                return built_in_equals(evaluated_arguments);
             }
             case Built_In_Pair: {
                 if (arguments_length != 2) {
@@ -536,46 +521,12 @@ Ast_Node* eval_expr(Ast_Node* node, Environment* env) {
                 return evaluated_arguments;
             }
             case Built_In_Print: {
-                /* if (arguments_length != 1) { */
-                /*     report_error(Error_Type_Wrong_Number_Of_Arguments); */
-                /* } */
-                /* print(evaluated_arguments->value.pair->first); */
-                /* printf("\n"); */
-                /* return arguments->value.pair->first; */
-
-                if (evaluated_and_parsed_arguments->positional_arguments->next_index == 0) {
+                if (arguments_length != 1) {
                     report_error(Error_Type_Wrong_Number_Of_Arguments);
                 }
-
-                char* sep = " ";
-                char* end = "\n";
-
-                Ast_Node* temp = extract_keyword_value("sep", evaluated_and_parsed_arguments);
-                if (temp) {
-                    try {
-                        assert_type(temp, Ast_Node_Type_String);
-                    }
-                    sep = temp->value.string->value;
-                }
-
-                temp = extract_keyword_value("end", evaluated_and_parsed_arguments);
-                if (temp) {
-                    try {
-                        assert_type(temp, Ast_Node_Type_String);
-                    }
-                    end = temp->value.string->value;
-                }
-
-                print(*evaluated_and_parsed_arguments->positional_arguments->data);
-                for (int i = 1; i < evaluated_and_parsed_arguments->positional_arguments->next_index; ++i) {
-                    printf("%s", sep);
-                    print(*(evaluated_and_parsed_arguments->positional_arguments->data+i));
-                }
-                printf("%s", end);
-
-                // return last positional argument
-                return *(evaluated_and_parsed_arguments->positional_arguments->data+
-                         (evaluated_and_parsed_arguments->positional_arguments->next_index-1));
+                print(evaluated_arguments->value.pair->first);
+                printf("\n");
+                return arguments->value.pair->first;
             }
             case Built_In_Read: {
                 if (arguments_length > 1) {
@@ -635,7 +586,7 @@ Ast_Node* eval_expr(Ast_Node* node, Environment* env) {
         if (operator->type == Ast_Node_Type_Function) {
             Ast_Node* result;
             try {
-                result = apply_arguments_to_function(arguments, operator);
+                result = apply_arguments_to_function(arguments, operator->value.function, env);
             }
             return result;
         }
diff --git a/vs/slime.sln b/vs/slime.sln
index d61dfe6..043c57f 100644
--- a/vs/slime.sln
+++ b/vs/slime.sln
@@ -6,6 +6,9 @@ MinimumVisualStudioVersion = 10.0.40219.1
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "slime", "slime.vcxproj", "{1A47A3ED-871F-4CB4-875B-8CAA385B1771}"
 EndProject
 Global
+	GlobalSection(Performance) = preSolution
+		HasPerformanceSessions = true
+	EndGlobalSection
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|x64 = Debug|x64
 		Debug|x86 = Debug|x86