diff --git a/include/types.hpp b/include/types.hpp
index f6c99f6..3af1975 100644
--- a/include/types.hpp
+++ b/include/types.hpp
@@ -8,6 +8,7 @@
 #include <unordered_map>
 
 // for clangd
+#include "error_handling.hpp"
 #include "utils.hpp"
 
 namespace info::type {
@@ -49,6 +50,11 @@ public:
   }
 
   bool HasTypeclass(utils::IdType graph_id) {
+    error_handling::DebugPrint(name_);
+    error_handling::DebugPrint(requirement_graph_ids_.size());
+    for (auto& requirement_graph_id : requirement_graph_ids_) {
+      error_handling::DebugPrint(requirement_graph_id);
+    }
     return requirement_graph_ids_.count(graph_id) != 0;
   }
 
diff --git a/include/utils.hpp b/include/utils.hpp
index b2c9802..cfa30f4 100644
--- a/include/utils.hpp
+++ b/include/utils.hpp
@@ -69,21 +69,21 @@ inline bool IsBuiltinFunction(const std::string& name) { // optimize ??
   builtin_functions.insert("+=");
   builtin_functions.insert("-=");
   builtin_functions.insert("*=");
-  builtin_functions.insert("//=");
-  builtin_functions.insert("%=");
+  builtin_functions.insert("div");
+  builtin_functions.insert("mod");
   builtin_functions.insert("/=");
-  builtin_functions.insert("+");
-  builtin_functions.insert("-");
-  builtin_functions.insert("*");
-  builtin_functions.insert("//");
-  builtin_functions.insert("%");
-  builtin_functions.insert("/");
+  // builtin_functions.insert("+");
+  // builtin_functions.insert("-");
+  // builtin_functions.insert("*");
+  // builtin_functions.insert("/");
   builtin_functions.insert("&&");
   builtin_functions.insert("||");
   builtin_functions.insert("size");
   builtin_functions.insert("random");
   builtin_functions.insert("print");
   builtin_functions.insert("scan");
+  builtin_functions.insert("zero");
+  builtin_functions.insert("one");
 
   return builtin_functions.count(name) != 0;
 }
diff --git a/src/build_visitor.cpp b/src/build_visitor.cpp
index 6982618..ca0a941 100644
--- a/src/build_visitor.cpp
+++ b/src/build_visitor.cpp
@@ -902,7 +902,7 @@ void BuildVisitor::VisitBinaryOperatorExpression(FunctionCallExpression* node) {
       FunctionCallExpression* argument_node = std::get<std::unique_ptr<FunctionCallExpression>>(node->arguments[i]).get();
       if (argument_node->is_binary_operator_expression
           && argument_node->precedence.has_value()
-          && argument_node->precedence.value() >= node->precedence.value()) {
+          && argument_node->precedence.value() == node->precedence.value()) {
         error_handling::HandleParsingError("Operators can't be chained (left argument)", node->base.start_position, node->base.end_position);
       }
     }
diff --git a/tests/.test_code.lang.kate-swp b/tests/.test_code.lang.kate-swp
deleted file mode 100644
index c343296..0000000
Binary files a/tests/.test_code.lang.kate-swp and /dev/null differ
diff --git a/tests/stdlib.lang b/tests/stdlib.lang
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_code.lang b/tests/test_code.lang
index 7f574d3..eac5aea 100644
--- a/tests/test_code.lang
+++ b/tests/test_code.lang
@@ -1,7 +1,7 @@
-basic (Float : #Ord)
-basic (Int : #Ord)
+basic (Float : #Ord #Div)
+basic (Int : #Ord #IDiv)
 basic (String : #Ord)
-basic (Char : #Ord)
+basic (Char : #Ord #Enum)
 basic (Bool : #Ord)
 basic Unit
 
@@ -33,7 +33,70 @@ def ( || ) : x y =
         | false -> false
     )
 
-// Eq typeclass
+//
+
+typeclass Move =
+  & var ( <- ) : Move -> Unit // TODO
+
+typeclass Copy =
+  & var ( = ) : Copy -> Unit
+
+//
+
+typeclass (Sum : #Copy) =
+  & var ( += ) : Sum -> Unit
+  & var ( -= ) : Sum -> Unit
+  & var ( + ) : Sum -> Sum
+  & var ( - ) : Sum -> Sum
+  & zero : -> Sum
+
+namespace var Sum {
+  def ( + ) : x = {
+    var ans = self
+    ; ans += x
+    return ans
+  }
+
+  def ( - ) : x = {
+    var ans = self
+    ; ans -= x
+    return ans
+  }
+}
+
+typeclass (Mult : #Sum) =
+  & var ( *= ) : Mult -> Unit
+  & var ( * ) : Mult -> Mult
+
+namespace var Mult {
+  def ( * ) : x = {
+    var ans = self
+    ; ans *= x
+    return ans
+  }
+}
+
+typeclass (IDiv : #Mult) =
+  & var div : IDiv -> Unit
+  & var mod : IDiv -> Unit
+
+namespace var IDiv {
+  def mod : x = self -. x * self.div: x
+}
+
+typeclass (Div : #Mult) =
+  & var ( /= ) : Div -> Unit
+  & var ( / ) : Div -> Div
+
+namespace var Div {
+  def ( / ) : x = {
+    var ans = self
+    ; ans /= x
+    return ans
+  }
+}
+
+//
 
 typeclass Eq =
   & var ( == ) : Eq -> Bool
@@ -82,8 +145,8 @@ typeclass Show =
 typeclass Read =
   & var read : String -> Read
 
-typeclass Debug =
-  & debug : -> String
+typeclass DebugShow =
+  & debug_show : -> String
 
 //
 
@@ -141,7 +204,7 @@ def func : s = {
 }
 
 exec main {
-  for i in (,0 ,1 ,2 ,3) do func: "abacaba"
+  for i in 0--9 do func: "abacaba"
   ; print: ({
     if true then bring scan: else { ; print: "aaa" }
     bring "nothing"