diff --git a/phasm/codestyle.py b/phasm/codestyle.py
index d6f57bb..1e21daf 100644
--- a/phasm/codestyle.py
+++ b/phasm/codestyle.py
@@ -116,10 +116,6 @@ def expression(inp: ourlang.Expression) -> str:
     if isinstance(inp, ourlang.AccessStructMember):
         return f'{expression(inp.varref)}.{inp.member}'
 
-    if isinstance(inp, ourlang.Fold):
-        fold_name = 'foldl' if ourlang.Fold.Direction.LEFT == inp.dir else 'foldr'
-        return f'{fold_name}({inp.func.name}, {expression(inp.base)}, {expression(inp.iter)})'
-
     raise NotImplementedError(expression, inp)
 
 def statement(inp: ourlang.Statement) -> Statements:
diff --git a/phasm/compiler.py b/phasm/compiler.py
index 9d8cc0e..fb34d9e 100644
--- a/phasm/compiler.py
+++ b/phasm/compiler.py
@@ -4,7 +4,7 @@ This module contains the code to convert parsed Ourlang into WebAssembly code
 import struct
 from typing import Dict, List, Optional
 
-from . import codestyle, ourlang, prelude, wasm
+from . import ourlang, prelude, wasm
 from .runtime import calculate_alloc_size, calculate_member_offset
 from .stdlib import alloc as stdlib_alloc
 from .stdlib import types as stdlib_types
@@ -587,89 +587,85 @@ def expression(wgn: WasmGenerator, inp: ourlang.Expression) -> None:
         )))
         return
 
-    if isinstance(inp, ourlang.Fold):
-        expression_fold(wgn, inp)
-        return
-
     raise NotImplementedError(expression, inp)
 
-def expression_fold(wgn: WasmGenerator, inp: ourlang.Fold) -> None:
-    """
-    Compile: Fold expression
-    """
-    assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
+# def expression_fold(wgn: WasmGenerator, inp: ourlang.Fold) -> None:
+#     """
+#     Compile: Fold expression
+#     """
+#     assert isinstance(inp.type3, type3types.Type3), type3placeholders.TYPE3_ASSERTION_ERROR
 
-    if inp.iter.type3 is not prelude.bytes_:
-        raise NotImplementedError(expression_fold, inp, inp.iter.type3)
+#     if inp.iter.type3 is not prelude.bytes_:
+#         raise NotImplementedError(expression_fold, inp, inp.iter.type3)
 
-    wgn.add_statement('nop', comment='acu :: u8')
-    acu_var = wgn.temp_var_u8(f'fold_{codestyle.type3(inp.type3)}_acu')
-    wgn.add_statement('nop', comment='adr :: bytes*')
-    adr_var = wgn.temp_var_i32('fold_i32_adr')
-    wgn.add_statement('nop', comment='len :: i32')
-    len_var = wgn.temp_var_i32('fold_i32_len')
+#     wgn.add_statement('nop', comment='acu :: u8')
+#     acu_var = wgn.temp_var_u8(f'fold_{codestyle.type3(inp.type3)}_acu')
+#     wgn.add_statement('nop', comment='adr :: bytes*')
+#     adr_var = wgn.temp_var_i32('fold_i32_adr')
+#     wgn.add_statement('nop', comment='len :: i32')
+#     len_var = wgn.temp_var_i32('fold_i32_len')
 
-    wgn.add_statement('nop', comment='acu = base')
-    expression(wgn, inp.base)
-    wgn.local.set(acu_var)
+#     wgn.add_statement('nop', comment='acu = base')
+#     expression(wgn, inp.base)
+#     wgn.local.set(acu_var)
 
-    wgn.add_statement('nop', comment='adr = adr(iter)')
-    expression(wgn, inp.iter)
-    wgn.local.set(adr_var)
+#     wgn.add_statement('nop', comment='adr = adr(iter)')
+#     expression(wgn, inp.iter)
+#     wgn.local.set(adr_var)
 
-    wgn.add_statement('nop', comment='len = len(iter)')
-    wgn.local.get(adr_var)
-    wgn.i32.load()
-    wgn.local.set(len_var)
+#     wgn.add_statement('nop', comment='len = len(iter)')
+#     wgn.local.get(adr_var)
+#     wgn.i32.load()
+#     wgn.local.set(len_var)
 
-    wgn.add_statement('nop', comment='i = 0')
-    idx_var = wgn.temp_var_i32(f'fold_{codestyle.type3(inp.type3)}_idx')
-    wgn.i32.const(0)
-    wgn.local.set(idx_var)
+#     wgn.add_statement('nop', comment='i = 0')
+#     idx_var = wgn.temp_var_i32(f'fold_{codestyle.type3(inp.type3)}_idx')
+#     wgn.i32.const(0)
+#     wgn.local.set(idx_var)
 
-    wgn.add_statement('nop', comment='if i < len')
-    wgn.local.get(idx_var)
-    wgn.local.get(len_var)
-    wgn.i32.lt_u()
-    with wgn.if_():
-        # From here on, adr_var is the address of byte we're referencing
-        # This is akin to calling stdlib_types.__subscript_bytes__
-        # But since we already know we are inside of bounds,
-        # can just bypass it and load the memory directly.
-        wgn.local.get(adr_var)
-        wgn.i32.const(3) # Bytes header -1, since we do a +1 every loop
-        wgn.i32.add()
-        wgn.local.set(adr_var)
+#     wgn.add_statement('nop', comment='if i < len')
+#     wgn.local.get(idx_var)
+#     wgn.local.get(len_var)
+#     wgn.i32.lt_u()
+#     with wgn.if_():
+#         # From here on, adr_var is the address of byte we're referencing
+#         # This is akin to calling stdlib_types.__subscript_bytes__
+#         # But since we already know we are inside of bounds,
+#         # can just bypass it and load the memory directly.
+#         wgn.local.get(adr_var)
+#         wgn.i32.const(3) # Bytes header -1, since we do a +1 every loop
+#         wgn.i32.add()
+#         wgn.local.set(adr_var)
 
-        wgn.add_statement('nop', comment='while True')
-        with wgn.loop():
-            wgn.add_statement('nop', comment='acu = func(acu, iter[i])')
-            wgn.local.get(acu_var)
+#         wgn.add_statement('nop', comment='while True')
+#         with wgn.loop():
+#             wgn.add_statement('nop', comment='acu = func(acu, iter[i])')
+#             wgn.local.get(acu_var)
 
-            # Get the next byte, write back the address
-            wgn.local.get(adr_var)
-            wgn.i32.const(1)
-            wgn.i32.add()
-            wgn.local.tee(adr_var)
-            wgn.i32.load8_u()
+#             # Get the next byte, write back the address
+#             wgn.local.get(adr_var)
+#             wgn.i32.const(1)
+#             wgn.i32.add()
+#             wgn.local.tee(adr_var)
+#             wgn.i32.load8_u()
 
-            wgn.add_statement('call', f'${inp.func.name}')
-            wgn.local.set(acu_var)
+#             wgn.add_statement('call', f'${inp.func.name}')
+#             wgn.local.set(acu_var)
 
-            wgn.add_statement('nop', comment='i = i + 1')
-            wgn.local.get(idx_var)
-            wgn.i32.const(1)
-            wgn.i32.add()
-            wgn.local.set(idx_var)
+#             wgn.add_statement('nop', comment='i = i + 1')
+#             wgn.local.get(idx_var)
+#             wgn.i32.const(1)
+#             wgn.i32.add()
+#             wgn.local.set(idx_var)
 
-            wgn.add_statement('nop', comment='if i >= len: break')
-            wgn.local.get(idx_var)
-            wgn.local.get(len_var)
-            wgn.i32.lt_u()
-            wgn.br_if(0)
+#             wgn.add_statement('nop', comment='if i >= len: break')
+#             wgn.local.get(idx_var)
+#             wgn.local.get(len_var)
+#             wgn.i32.lt_u()
+#             wgn.br_if(0)
 
-    # return acu
-    wgn.local.get(acu_var)
+#     # return acu
+#     wgn.local.get(acu_var)
 
 def statement_return(wgn: WasmGenerator, inp: ourlang.StatementReturn) -> None:
     """
diff --git a/phasm/ourlang.py b/phasm/ourlang.py
index 77168df..9939683 100644
--- a/phasm/ourlang.py
+++ b/phasm/ourlang.py
@@ -1,7 +1,6 @@
 """
 Contains the syntax tree for ourlang
 """
-import enum
 from typing import Dict, Iterable, List, Optional, Union
 
 from . import prelude
@@ -222,36 +221,6 @@ class AccessStructMember(Expression):
         self.struct_type3 = struct_type3
         self.member = member
 
-class Fold(Expression):
-    """
-    A (left or right) fold
-    """
-    class Direction(enum.Enum):
-        """
-        Which direction to fold in
-        """
-        LEFT = 0
-        RIGHT = 1
-
-    dir: Direction
-    func: 'Function'
-    base: Expression
-    iter: Expression
-
-    def __init__(
-            self,
-            dir_: Direction,
-            func: 'Function',
-            base: Expression,
-            iter_: Expression,
-        ) -> None:
-        super().__init__()
-
-        self.dir = dir_
-        self.func = func
-        self.base = base
-        self.iter = iter_
-
 class Statement:
     """
     A statement within a function
diff --git a/phasm/parser.py b/phasm/parser.py
index ced7d6d..e81612c 100644
--- a/phasm/parser.py
+++ b/phasm/parser.py
@@ -14,7 +14,6 @@ from .ourlang import (
     ConstantStruct,
     ConstantTuple,
     Expression,
-    Fold,
     Function,
     FunctionCall,
     FunctionParam,
@@ -467,7 +466,7 @@ class OurVisitor:
 
         raise NotImplementedError(f'{node} as expr in FunctionDef')
 
-    def visit_Module_FunctionDef_Call(self, module: Module, function: Function, our_locals: OurLocals, node: ast.Call) -> Union[Fold, FunctionCall, UnaryOp]:
+    def visit_Module_FunctionDef_Call(self, module: Module, function: Function, our_locals: OurLocals, node: ast.Call) -> Union[FunctionCall, UnaryOp]:
         if node.keywords:
             _raise_static_error(node, 'Keyword calling not supported') # Yet?
 
@@ -490,28 +489,28 @@ class OurVisitor:
             )
             unary_op.type3 = prelude.u32
             return unary_op
-        elif node.func.id == 'foldl':
-            if 3 != len(node.args):
-                _raise_static_error(node, f'Function {node.func.id} requires 3 arguments but {len(node.args)} are given')
+        # elif node.func.id == 'foldl':
+        #     if 3 != len(node.args):
+        #         _raise_static_error(node, f'Function {node.func.id} requires 3 arguments but {len(node.args)} are given')
 
-            # TODO: This is not generic, you cannot return a function
-            subnode = node.args[0]
-            if not isinstance(subnode, ast.Name):
-                raise NotImplementedError(f'Calling methods that are not a name {subnode}')
-            if not isinstance(subnode.ctx, ast.Load):
-                _raise_static_error(subnode, 'Must be load context')
-            if subnode.id not in module.functions:
-                _raise_static_error(subnode, 'Reference to undefined function')
-            func = module.functions[subnode.id]
-            if 2 != len(func.posonlyargs):
-                _raise_static_error(node, f'Function {node.func.id} requires a function with 2 arguments but a function with {len(func.posonlyargs)} args is given')
+        #     # TODO: This is not generic, you cannot return a function
+        #     subnode = node.args[0]
+        #     if not isinstance(subnode, ast.Name):
+        #         raise NotImplementedError(f'Calling methods that are not a name {subnode}')
+        #     if not isinstance(subnode.ctx, ast.Load):
+        #         _raise_static_error(subnode, 'Must be load context')
+        #     if subnode.id not in module.functions:
+        #         _raise_static_error(subnode, 'Reference to undefined function')
+        #     func = module.functions[subnode.id]
+        #     if 2 != len(func.posonlyargs):
+        #         _raise_static_error(node, f'Function {node.func.id} requires a function with 2 arguments but a function with {len(func.posonlyargs)} args is given')
 
-            return Fold(
-                Fold.Direction.LEFT,
-                func,
-                self.visit_Module_FunctionDef_expr(module, function, our_locals, node.args[1]),
-                self.visit_Module_FunctionDef_expr(module, function, our_locals, node.args[2]),
-            )
+        #     return Fold(
+        #         Fold.Direction.LEFT,
+        #         func,
+        #         self.visit_Module_FunctionDef_expr(module, function, our_locals, node.args[1]),
+        #         self.visit_Module_FunctionDef_expr(module, function, our_locals, node.args[2]),
+        #     )
         else:
             if node.func.id not in module.functions:
                 _raise_static_error(node, 'Call to undefined function')
diff --git a/phasm/prelude/__init__.py b/phasm/prelude/__init__.py
index 06eda3c..d799c04 100644
--- a/phasm/prelude/__init__.py
+++ b/phasm/prelude/__init__.py
@@ -2,7 +2,12 @@
 The prelude are all the builtin types, type classes and methods
 """
 
-from ..type3.typeclasses import Type3Class, TypeVariable, instance_type_class
+from ..type3.typeclasses import (
+    Type3Class,
+    TypeConstructorVariable,
+    TypeVariable,
+    instance_type_class,
+)
 from ..type3.types import (
     Type3,
     TypeConstructor_StaticArray,
@@ -121,7 +126,8 @@ PRELUDE_TYPES: dict[str, Type3] = {
 }
 
 a = TypeVariable('a')
-
+b = TypeVariable('b')
+t = TypeConstructorVariable('t')
 
 InternalPassAsPointer = Type3Class('InternalPassAsPointer', [a], methods={}, operators={})
 """
@@ -247,6 +253,10 @@ Sized_ = Type3Class('Sized', [a], methods={
 
 instance_type_class(Sized_, bytes_)
 
+Foldable = Type3Class('Foldable', [t], methods={
+    'foldl': [[a, b, b], b, t(a), b],
+}, operators={})
+
 PRELUDE_TYPE_CLASSES = {
     'Eq': Eq,
     'Ord': Ord,
diff --git a/phasm/type3/constraints.py b/phasm/type3/constraints.py
index 26de593..237a04c 100644
--- a/phasm/type3/constraints.py
+++ b/phasm/type3/constraints.py
@@ -241,14 +241,10 @@ class MustImplementTypeClassConstraint(ConstraintBase):
     """
     __slots__ = ('type_class3', 'type3', )
 
-    type_class3: Union[str, typeclasses.Type3Class]
+    type_class3: typeclasses.Type3Class
     type3: placeholders.Type3OrPlaceholder
 
-    DATA = {
-        'bytes': {'Foldable'},
-    }
-
-    def __init__(self, type_class3: Union[str, typeclasses.Type3Class], type3: placeholders.Type3OrPlaceholder, comment: Optional[str] = None) -> None:
+    def __init__(self, type_class3: typeclasses.Type3Class, type3: placeholders.Type3OrPlaceholder, comment: Optional[str] = None) -> None:
         super().__init__(comment=comment)
 
         self.type_class3 = type_class3
@@ -262,12 +258,8 @@ class MustImplementTypeClassConstraint(ConstraintBase):
         if isinstance(typ, placeholders.PlaceholderForType):
             return RequireTypeSubstitutes()
 
-        if isinstance(self.type_class3, typeclasses.Type3Class):
-            if self.type_class3 in typ.classes:
-                return None
-        else:
-            if self.type_class3 in self.__class__.DATA.get(typ.name, set()):
-                return None
+        if self.type_class3 in typ.classes:
+            return None
 
         return Error(f'{typ.name} does not implement the {self.type_class3} type class')
 
diff --git a/phasm/type3/constraintsgenerator.py b/phasm/type3/constraintsgenerator.py
index 724993b..8b9b4d3 100644
--- a/phasm/type3/constraintsgenerator.py
+++ b/phasm/type3/constraintsgenerator.py
@@ -161,16 +161,6 @@ def expression(ctx: Context, inp: ourlang.Expression) -> ConstraintGenerator:
             comment=f'The type of a struct member reference is the same as the type of struct member {inp.struct_type3.name}.{inp.member}')
         return
 
-    if isinstance(inp, ourlang.Fold):
-        yield from expression(ctx, inp.base)
-        yield from expression(ctx, inp.iter)
-
-        yield SameTypeConstraint(inp.func.posonlyargs[0].type3, inp.func.returns_type3, inp.base.type3, inp.type3,
-            comment='foldl :: Foldable t => (b -> a -> b) -> b -> t a -> b')
-        yield MustImplementTypeClassConstraint('Foldable', inp.iter.type3)
-
-        return
-
     raise NotImplementedError(expression, inp)
 
 def statement_return(ctx: Context, fun: ourlang.Function, inp: ourlang.StatementReturn) -> ConstraintGenerator:
diff --git a/phasm/type3/typeclasses.py b/phasm/type3/typeclasses.py
index 01f3d02..bfec542 100644
--- a/phasm/type3/typeclasses.py
+++ b/phasm/type3/typeclasses.py
@@ -24,6 +24,27 @@ class TypeVariable:
     def __repr__(self) -> str:
         return f'TypeVariable({repr(self.letter)})'
 
+class TypeConstructorVariable:
+    __slots__ = ('letter', )
+
+    letter: str
+
+    def __init__(self, letter: str) -> None:
+        assert len(letter) == 1, f'{letter} is not a valid type variable'
+        self.letter = letter
+
+    def __hash__(self) -> int:
+        return hash(self.letter)
+
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, TypeVariable):
+            raise NotImplementedError
+
+        return self.letter == other.letter
+
+    def __repr__(self) -> str:
+        return f'TypeVariable({repr(self.letter)})'
+
 class TypeReference:
     __slots__ = ('name', )
 
@@ -45,14 +66,16 @@ class TypeReference:
     def __repr__(self) -> str:
         return f'TypeReference({repr(self.name)})'
 
+Signature = List[Union[Type3, TypeVariable, list[TypeVariable]]]
+
 class Type3ClassMethod:
     __slots__ = ('type3_class', 'name', 'signature', )
 
     type3_class: 'Type3Class'
     name: str
-    signature: List[Union[Type3, TypeVariable]]
+    signature: Signature
 
-    def __init__(self, type3_class: 'Type3Class', name: str, signature: Iterable[Union[Type3, TypeVariable]]) -> None:
+    def __init__(self, type3_class: 'Type3Class', name: str, signature: Signature) -> None:
         self.type3_class = type3_class
         self.name = name
         self.signature = list(signature)
@@ -64,7 +87,7 @@ class Type3Class:
     __slots__ = ('name', 'args', 'methods', 'operators', 'inherited_classes', )
 
     name: str
-    args: List[TypeVariable]
+    args: List[Union[TypeVariable, TypeConstructorVariable]]
     methods: Dict[str, Type3ClassMethod]
     operators: Dict[str, Type3ClassMethod]
     inherited_classes: List['Type3Class']
@@ -72,9 +95,9 @@ class Type3Class:
     def __init__(
             self,
             name: str,
-            args: Iterable[TypeVariable],
-            methods: Mapping[str, Iterable[Union[Type3, TypeVariable]]],
-            operators: Mapping[str, Iterable[Union[Type3, TypeVariable]]],
+            args: Iterable[Union[TypeVariable, TypeConstructorVariable]],
+            methods: Mapping[str, Signature],
+            operators: Mapping[str, Signature],
             inherited_classes: Optional[List['Type3Class']] = None,
         ) -> None:
         self.name = name