diff --git a/nac3core/src/codegen/builtin_fns.rs b/nac3core/src/codegen/builtin_fns.rs
index 9914d81c..3ac65237 100644
--- a/nac3core/src/codegen/builtin_fns.rs
+++ b/nac3core/src/codegen/builtin_fns.rs
@@ -4,8 +4,7 @@ use inkwell::{FloatPredicate, IntPredicate, OptimizationLevel};
 use itertools::Itertools;
 
 use crate::codegen::classes::{
-    ArrayLikeValue, NDArrayValue, ProxyValue, RangeValue, TypedArrayLikeAccessor,
-    UntypedArrayLikeAccessor, UntypedArrayLikeMutator,
+    NDArrayValue, ProxyValue, RangeValue, UntypedArrayLikeAccessor, UntypedArrayLikeMutator,
 };
 use crate::codegen::expr::destructure_range;
 use crate::codegen::irrt::calculate_len_for_slice_range;
@@ -16,6 +15,12 @@ use crate::toplevel::helper::PrimDef;
 use crate::toplevel::numpy::unpack_ndarray_var_tys;
 use crate::typecheck::typedef::{Type, TypeEnum};
 
+use super::model::*;
+use super::object::any::AnyObject;
+use super::object::list::ListObject;
+use super::object::ndarray::NDArrayObject;
+use super::object::tuple::TupleObject;
+
 /// Shorthand for [`unreachable!()`] when a type of argument is not supported.
 ///
 /// The generated message will contain the function name and the name of the unsupported type.
@@ -32,58 +37,33 @@ pub fn call_len<'ctx, G: CodeGenerator + ?Sized>(
     ctx: &mut CodeGenContext<'ctx, '_>,
     n: (Type, BasicValueEnum<'ctx>),
 ) -> Result<IntValue<'ctx>, String> {
-    let llvm_i32 = ctx.ctx.i32_type();
-    let range_ty = ctx.primitives.range;
     let (arg_ty, arg) = n;
-
-    Ok(if ctx.unifier.unioned(arg_ty, range_ty) {
+    Ok(if ctx.unifier.unioned(arg_ty, ctx.primitives.range) {
         let arg = RangeValue::from_ptr_val(arg.into_pointer_value(), Some("range"));
         let (start, end, step) = destructure_range(ctx, arg);
         calculate_len_for_slice_range(generator, ctx, start, end, step)
     } else {
-        match &*ctx.unifier.get_ty_immutable(arg_ty) {
-            TypeEnum::TTuple { ty, .. } => llvm_i32.const_int(ty.len() as u64, false),
-            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::List.id() => {
-                let zero = llvm_i32.const_zero();
-                let len = ctx
-                    .build_gep_and_load(
-                        arg.into_pointer_value(),
-                        &[zero, llvm_i32.const_int(1, false)],
-                        None,
-                    )
-                    .into_int_value();
-                ctx.builder.build_int_truncate_or_bit_cast(len, llvm_i32, "len").unwrap()
+        let arg = AnyObject { ty: arg_ty, value: arg };
+        let len: Instance<'ctx, Int<Int32>> = match &*ctx.unifier.get_ty(arg_ty) {
+            TypeEnum::TTuple { .. } => {
+                let tuple = TupleObject::from_object(ctx, arg);
+                tuple.len(generator, ctx).truncate_or_bit_cast(generator, ctx, Int32)
             }
-            TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::NDArray.id() => {
-                let llvm_usize = generator.get_size_type(ctx.ctx);
-
-                let arg = NDArrayValue::from_ptr_val(arg.into_pointer_value(), llvm_usize, None);
-
-                let ndims = arg.dim_sizes().size(ctx, generator);
-                ctx.make_assert(
-                    generator,
-                    ctx.builder
-                        .build_int_compare(IntPredicate::NE, ndims, llvm_usize.const_zero(), "")
-                        .unwrap(),
-                    "0:TypeError",
-                    "len() of unsized object",
-                    [None, None, None],
-                    ctx.current_loc,
-                );
-
-                let len = unsafe {
-                    arg.dim_sizes().get_typed_unchecked(
-                        ctx,
-                        generator,
-                        &llvm_usize.const_zero(),
-                        None,
-                    )
-                };
-
-                ctx.builder.build_int_truncate_or_bit_cast(len, llvm_i32, "len").unwrap()
+            TypeEnum::TObj { obj_id, .. }
+                if *obj_id == ctx.primitives.ndarray.obj_id(&ctx.unifier).unwrap() =>
+            {
+                let ndarray = NDArrayObject::from_object(generator, ctx, arg);
+                ndarray.len(generator, ctx).truncate_or_bit_cast(generator, ctx, Int32)
             }
-            _ => unreachable!(),
-        }
+            TypeEnum::TObj { obj_id, .. }
+                if *obj_id == ctx.primitives.list.obj_id(&ctx.unifier).unwrap() =>
+            {
+                let list = ListObject::from_object(generator, ctx, arg);
+                list.len(generator, ctx).truncate_or_bit_cast(generator, ctx, Int32)
+            }
+            _ => unsupported_type(ctx, "len", &[arg_ty]),
+        };
+        len.value
     })
 }