diff --git a/nac3artiq/src/lib.rs b/nac3artiq/src/lib.rs
index 0af1bfcd..813f7984 100644
--- a/nac3artiq/src/lib.rs
+++ b/nac3artiq/src/lib.rs
@@ -1,12 +1,10 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::fs;
 use std::path::Path;
 use std::process::Command;
 use std::sync::Arc;
 
 use inkwell::{
-    AddressSpace, AtomicOrdering,
-    values::BasicValueEnum,
     passes::{PassManager, PassManagerBuilder},
     targets::*,
     OptimizationLevel,
@@ -18,13 +16,13 @@ use rustpython_parser::{
     parser,
 };
 
-use parking_lot::RwLock;
+use parking_lot::{RwLock, Mutex};
 
 use nac3core::{
     codegen::{CodeGenTask, WithCall, WorkerRegistry},
     symbol_resolver::SymbolResolver,
-    toplevel::{composer::TopLevelComposer, TopLevelContext, TopLevelDef, GenCall},
-    typecheck::typedef::{FunSignature, FuncArg},
+    toplevel::{composer::TopLevelComposer, TopLevelContext, TopLevelDef},
+    typecheck::typedef::FunSignature,
 };
 use nac3core::{
     toplevel::DefinitionId,
@@ -33,6 +31,7 @@ use nac3core::{
 
 use crate::symbol_resolver::Resolver;
 
+mod builtins;
 mod symbol_resolver;
 
 #[derive(PartialEq, Clone, Copy)]
@@ -41,6 +40,17 @@ enum Isa {
     CortexA9,
 }
 
+#[derive(Clone)]
+pub struct PrimitivePythonId {
+    int: u64,
+    int32: u64,
+    int64: u64,
+    float: u64,
+    bool: u64,
+    list: u64,
+    tuple: u64,
+}
+
 // TopLevelComposer is unsendable as it holds the unification table, which is
 // unsendable due to Rc. Arc would cause a performance hit.
 #[pyclass(unsendable, name = "NAC3")]
@@ -54,6 +64,8 @@ struct Nac3 {
     composer: TopLevelComposer,
     top_level: Option<Arc<TopLevelContext>>,
     to_be_registered: Vec<PyObject>,
+    primitive_ids: PrimitivePythonId,
+    global_value_ids: Arc<Mutex<HashSet<u64>>>,
 }
 
 impl Nac3 {
@@ -81,16 +93,18 @@ impl Nac3 {
         let source = fs::read_to_string(source_file).map_err(|e| {
             exceptions::PyIOError::new_err(format!("failed to read input file: {}", e))
         })?;
-        let parser_result = parser::parse_program(&source).map_err(|e| {
-            exceptions::PySyntaxError::new_err(format!("parse error: {}", e))
-        })?;
+        let parser_result = parser::parse_program(&source)
+            .map_err(|e| exceptions::PySyntaxError::new_err(format!("parse error: {}", e)))?;
         let resolver = Arc::new(Box::new(Resolver {
             id_to_type: self.builtins_ty.clone().into(),
             id_to_def: self.builtins_def.clone().into(),
             pyid_to_def: self.pyid_to_def.clone(),
             pyid_to_type: self.pyid_to_type.clone(),
+            primitive_ids: self.primitive_ids.clone(),
+            global_value_ids: self.global_value_ids.clone(),
             class_names: Default::default(),
             name_to_pyid: name_to_pyid.clone(),
+            module: obj,
         }) as Box<dyn SymbolResolver + Send + Sync>);
         let mut name_to_def = HashMap::new();
         let mut name_to_type = HashMap::new();
@@ -163,128 +177,76 @@ impl Nac3 {
     }
 }
 
-// ARTIQ timeline control with now-pinning optimization.
-fn timeline_builtins(primitive: &PrimitiveStore) -> Vec<(StrRef, FunSignature, Arc<GenCall>)> {
-    vec![(
-        "now_mu".into(),
-        FunSignature {
-            args: vec![],
-            ret: primitive.int64,
-            vars: HashMap::new(),
-        },
-        Arc::new(GenCall::new(Box::new(
-            |ctx, _, _, _| {
-                let i64_type = ctx.ctx.i64_type();
-                let now = ctx.module.get_global("now").unwrap_or_else(|| ctx.module.add_global(i64_type, None, "now"));
-                let now_raw = ctx.builder.build_load(now.as_pointer_value(), "now");
-                if let BasicValueEnum::IntValue(now_raw) = now_raw {
-                    let i64_32 = i64_type.const_int(32, false).into();
-                    let now_lo = ctx.builder.build_left_shift(now_raw, i64_32, "now_shl");
-                    let now_hi = ctx.builder.build_right_shift(now_raw, i64_32, false, "now_lshr").into();
-                    Some(ctx.builder.build_or(now_lo, now_hi, "now_or").into())
-                } else {
-                    unreachable!()
-                }
-            }
-        )))
-    ),(
-        "at_mu".into(),
-        FunSignature {
-            args: vec![FuncArg {
-                name: "t".into(),
-                ty: primitive.int64,
-                default_value: None,
-            }],
-            ret: primitive.none,
-            vars: HashMap::new(),
-        },
-        Arc::new(GenCall::new(Box::new(
-            |ctx, _, _, args| {
-                let i32_type = ctx.ctx.i32_type();
-                let i64_type = ctx.ctx.i64_type();
-                let i64_32 = i64_type.const_int(32, false).into();
-                if let BasicValueEnum::IntValue(time) = args[0].1 {
-                    let time_hi = ctx.builder.build_int_truncate(ctx.builder.build_right_shift(time, i64_32, false, "now_lshr"), i32_type, "now_trunc");
-                    let time_lo = ctx.builder.build_int_truncate(time, i32_type, "now_trunc");
-                    let now = ctx.module.get_global("now").unwrap_or_else(|| ctx.module.add_global(i64_type, None, "now"));
-                    let now_hiptr = ctx.builder.build_bitcast(now, i32_type.ptr_type(AddressSpace::Generic), "now_bitcast");
-                    if let BasicValueEnum::PointerValue(now_hiptr) = now_hiptr {
-                        let now_loptr = unsafe { ctx.builder.build_gep(now_hiptr, &[i32_type.const_int(1, false).into()], "now_gep") };
-                        ctx.builder.build_store(now_hiptr, time_hi).set_atomic_ordering(AtomicOrdering::SequentiallyConsistent).unwrap();
-                        ctx.builder.build_store(now_loptr, time_lo).set_atomic_ordering(AtomicOrdering::SequentiallyConsistent).unwrap();
-                        None
-                    } else {
-                        unreachable!();
-                    }
-                } else {
-                    unreachable!();
-                }
-            }
-        )))
-    ),(
-        "delay_mu".into(),
-        FunSignature {
-            args: vec![FuncArg {
-                name: "dt".into(),
-                ty: primitive.int64,
-                default_value: None,
-            }],
-            ret: primitive.none,
-            vars: HashMap::new(),
-        },
-        Arc::new(GenCall::new(Box::new(
-            |ctx, _, _, args| {
-                let i32_type = ctx.ctx.i32_type();
-                let i64_type = ctx.ctx.i64_type();
-                let i64_32 = i64_type.const_int(32, false).into();
-                let now = ctx.module.get_global("now").unwrap_or_else(|| ctx.module.add_global(i64_type, None, "now"));
-                let now_raw = ctx.builder.build_load(now.as_pointer_value(), "now");
-                if let (BasicValueEnum::IntValue(now_raw), BasicValueEnum::IntValue(dt)) = (now_raw, args[0].1) {
-                    let now_lo = ctx.builder.build_left_shift(now_raw, i64_32, "now_shl");
-                    let now_hi = ctx.builder.build_right_shift(now_raw, i64_32, false, "now_lshr").into();
-                    let now_val = ctx.builder.build_or(now_lo, now_hi, "now_or");
-                    let time = ctx.builder.build_int_add(now_val, dt, "now_add");
-                    let time_hi = ctx.builder.build_int_truncate(ctx.builder.build_right_shift(time, i64_32, false, "now_lshr"), i32_type, "now_trunc");
-                    let time_lo = ctx.builder.build_int_truncate(time, i32_type, "now_trunc");
-                    let now_hiptr = ctx.builder.build_bitcast(now, i32_type.ptr_type(AddressSpace::Generic), "now_bitcast");
-                    if let BasicValueEnum::PointerValue(now_hiptr) = now_hiptr {
-                        let now_loptr = unsafe { ctx.builder.build_gep(now_hiptr, &[i32_type.const_int(1, false).into()], "now_gep") };
-                        ctx.builder.build_store(now_hiptr, time_hi).set_atomic_ordering(AtomicOrdering::SequentiallyConsistent).unwrap();
-                        ctx.builder.build_store(now_loptr, time_lo).set_atomic_ordering(AtomicOrdering::SequentiallyConsistent).unwrap();
-                        None
-                    } else {
-                        unreachable!();
-                    }
-                } else {
-                    unreachable!();
-                }
-            }
-        )))
-    )]
-}
-
 #[pymethods]
 impl Nac3 {
     #[new]
-    fn new(isa: &str) -> PyResult<Self> {
+    fn new(isa: &str, py: Python) -> PyResult<Self> {
         let isa = match isa {
             "riscv" => Isa::RiscV,
             "cortexa9" => Isa::CortexA9,
             _ => return Err(exceptions::PyValueError::new_err("invalid ISA")),
         };
         let primitive: PrimitiveStore = TopLevelComposer::make_primitives().0;
-        let builtins = if isa == Isa::RiscV { timeline_builtins(&primitive) } else { vec![] };
+        let builtins = if isa == Isa::RiscV {
+            builtins::timeline_builtins(&primitive)
+        } else {
+            vec![]
+        };
         let (composer, builtins_def, builtins_ty) = TopLevelComposer::new(builtins);
+
+        let builtins_mod = PyModule::import(py, "builtins").unwrap();
+        let id_fn = builtins_mod.getattr("id").unwrap();
+        let numpy_mod = PyModule::import(py, "numpy").unwrap();
+        let primitive_ids = PrimitivePythonId {
+            int: id_fn
+                .call1((builtins_mod.getattr("int").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            int32: id_fn
+                .call1((numpy_mod.getattr("int32").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            int64: id_fn
+                .call1((numpy_mod.getattr("int64").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            bool: id_fn
+                .call1((builtins_mod.getattr("bool").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            float: id_fn
+                .call1((builtins_mod.getattr("float").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            list: id_fn
+                .call1((builtins_mod.getattr("list").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+            tuple: id_fn
+                .call1((builtins_mod.getattr("tuple").unwrap(),))
+                .unwrap()
+                .extract()
+                .unwrap(),
+        };
+
         Ok(Nac3 {
             isa,
             primitive,
             builtins_ty,
             builtins_def,
             composer,
+            primitive_ids,
             top_level: None,
             pyid_to_def: Default::default(),
             pyid_to_type: Default::default(),
             to_be_registered: Default::default(),
+            global_value_ids: Default::default(),
         })
     }
 
@@ -301,7 +263,7 @@ impl Nac3 {
         Ok(())
     }
 
-    fn compile_method(&mut self, class: u64, method_name: String) -> PyResult<()> {
+    fn compile_method(&mut self, class: u64, method_name: String, py: Python) -> PyResult<()> {
         let top_level = self.top_level.as_ref().unwrap();
         let module_resolver;
         let instance = {
@@ -356,7 +318,7 @@ impl Nac3 {
         let isa = self.isa;
         let f = Arc::new(WithCall::new(Box::new(move |module| {
             let builder = PassManagerBuilder::create();
-            builder.set_optimization_level(OptimizationLevel::Aggressive);
+            builder.set_optimization_level(OptimizationLevel::Default);
             let passes = PassManager::create(());
             builder.populate_module_pass_manager(&passes);
             passes.run_on(module);
@@ -390,9 +352,13 @@ impl Nac3 {
         })));
         let thread_names: Vec<String> = (0..4).map(|i| format!("module{}", i)).collect();
         let threads: Vec<_> = thread_names.iter().map(|s| s.as_str()).collect();
-        let (registry, handles) = WorkerRegistry::create_workers(&threads, top_level.clone(), f);
-        registry.add_task(task);
-        registry.wait_tasks_complete(handles);
+
+        py.allow_threads(|| {
+            let (registry, handles) =
+                WorkerRegistry::create_workers(&threads, top_level.clone(), f);
+            registry.add_task(task);
+            registry.wait_tasks_complete(handles);
+        });
 
         let mut linker_args = vec![
             "-shared".to_string(),
diff --git a/nac3artiq/src/symbol_resolver.rs b/nac3artiq/src/symbol_resolver.rs
index f163de64..1b1c62e9 100644
--- a/nac3artiq/src/symbol_resolver.rs
+++ b/nac3artiq/src/symbol_resolver.rs
@@ -1,32 +1,348 @@
+use inkwell::{types::BasicType, values::BasicValueEnum, AddressSpace};
 use nac3core::{
+    codegen::CodeGenContext,
     location::Location,
-    symbol_resolver::{SymbolResolver, SymbolValue},
-    toplevel::DefinitionId,
+    symbol_resolver::SymbolResolver,
+    toplevel::{DefinitionId, TopLevelDef},
     typecheck::{
         type_inferencer::PrimitiveStore,
-        typedef::{Type, Unifier},
+        typedef::{Type, TypeEnum, Unifier},
     },
 };
 use parking_lot::{Mutex, RwLock};
+use pyo3::{
+    types::{PyList, PyModule, PyTuple},
+    PyAny, PyObject, PyResult, Python,
+};
 use rustpython_parser::ast::StrRef;
-use std::{collections::HashMap, sync::Arc};
+use std::{
+    collections::{HashMap, HashSet},
+    sync::Arc,
+};
+
+use crate::PrimitivePythonId;
 
 pub struct Resolver {
     pub id_to_type: Mutex<HashMap<StrRef, Type>>,
     pub id_to_def: Mutex<HashMap<StrRef, DefinitionId>>,
+    pub global_value_ids: Arc<Mutex<HashSet<u64>>>,
     pub class_names: Mutex<HashMap<StrRef, Type>>,
     pub pyid_to_def: Arc<RwLock<HashMap<u64, DefinitionId>>>,
     pub pyid_to_type: Arc<RwLock<HashMap<u64, Type>>>,
+    pub primitive_ids: PrimitivePythonId,
     // module specific
     pub name_to_pyid: HashMap<StrRef, u64>,
+    pub module: PyObject,
+}
+
+struct PythonHelper<'a> {
+    type_fn: &'a PyAny,
+    len_fn: &'a PyAny,
+    id_fn: &'a PyAny,
+}
+
+impl Resolver {
+    fn get_list_elem_type(
+        &self,
+        list: &PyAny,
+        len: usize,
+        helper: &PythonHelper,
+        unifier: &mut Unifier,
+        defs: &[Arc<RwLock<TopLevelDef>>],
+        primitives: &PrimitiveStore,
+    ) -> PyResult<Option<Type>> {
+        let first = self.get_obj_type(list.get_item(0)?, helper, unifier, defs, primitives)?;
+        Ok((1..len).fold(first, |a, i| {
+            let b = list
+                .get_item(i)
+                .map(|elem| self.get_obj_type(elem, helper, unifier, defs, primitives));
+            a.and_then(|a| {
+                if let Ok(Ok(Some(ty))) = b {
+                    if unifier.unify(a, ty).is_ok() {
+                        Some(a)
+                    } else {
+                        None
+                    }
+                } else {
+                    None
+                }
+            })
+        }))
+    }
+
+    fn get_obj_type(
+        &self,
+        obj: &PyAny,
+        helper: &PythonHelper,
+        unifier: &mut Unifier,
+        defs: &[Arc<RwLock<TopLevelDef>>],
+        primitives: &PrimitiveStore,
+    ) -> PyResult<Option<Type>> {
+        let ty_id: u64 = helper
+            .id_fn
+            .call1((helper.type_fn.call1((obj,))?,))?
+            .extract()?;
+
+        if ty_id == self.primitive_ids.int || ty_id == self.primitive_ids.int32 {
+            Ok(Some(primitives.int32))
+        } else if ty_id == self.primitive_ids.int64 {
+            Ok(Some(primitives.int64))
+        } else if ty_id == self.primitive_ids.bool {
+            Ok(Some(primitives.bool))
+        } else if ty_id == self.primitive_ids.float {
+            Ok(Some(primitives.float))
+        } else if ty_id == self.primitive_ids.list {
+            let len: usize = helper.len_fn.call1((obj,))?.extract()?;
+            if len == 0 {
+                let var = unifier.get_fresh_var().0;
+                let list = unifier.add_ty(TypeEnum::TList { ty: var });
+                Ok(Some(list))
+            } else {
+                let ty = self.get_list_elem_type(obj, len, helper, unifier, defs, primitives)?;
+                Ok(ty.map(|ty| unifier.add_ty(TypeEnum::TList { ty })))
+            }
+        } else if ty_id == self.primitive_ids.tuple {
+            let elements: &PyTuple = obj.cast_as()?;
+            let types: Result<Option<Vec<_>>, _> = elements
+                .iter()
+                .map(|elem| self.get_obj_type(elem, helper, unifier, defs, primitives))
+                .collect();
+            let types = types?;
+            Ok(types.map(|types| unifier.add_ty(TypeEnum::TTuple { ty: types })))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn get_obj_value<'ctx, 'a>(
+        &self,
+        obj: &PyAny,
+        helper: &PythonHelper,
+        ctx: &mut CodeGenContext<'ctx, 'a>,
+    ) -> PyResult<Option<BasicValueEnum<'ctx>>> {
+        let ty_id: u64 = helper
+            .id_fn
+            .call1((helper.type_fn.call1((obj,))?,))?
+            .extract()?;
+        if ty_id == self.primitive_ids.int || ty_id == self.primitive_ids.int32 {
+            let val: i32 = obj.extract()?;
+            Ok(Some(ctx.ctx.i32_type().const_int(val as u64, false).into()))
+        } else if ty_id == self.primitive_ids.int64 {
+            let val: i64 = obj.extract()?;
+            Ok(Some(ctx.ctx.i64_type().const_int(val as u64, false).into()))
+        } else if ty_id == self.primitive_ids.bool {
+            let val: bool = obj.extract()?;
+            Ok(Some(
+                ctx.ctx.bool_type().const_int(val as u64, false).into(),
+            ))
+        } else if ty_id == self.primitive_ids.float {
+            let val: f64 = obj.extract()?;
+            Ok(Some(ctx.ctx.f64_type().const_float(val).into()))
+        } else if ty_id == self.primitive_ids.list {
+            let id: u64 = helper.id_fn.call1((obj,))?.extract()?;
+            let id_str = id.to_string();
+            let len: usize = helper.len_fn.call1((obj,))?.extract()?;
+            if len == 0 {
+                let int32 = ctx.ctx.i32_type();
+                return Ok(Some(
+                    ctx.ctx
+                        .struct_type(
+                            &[int32.into(), int32.ptr_type(AddressSpace::Generic).into()],
+                            false,
+                        )
+                        .const_zero()
+                        .into(),
+                ));
+            }
+            let ty = self
+                .get_list_elem_type(
+                    obj,
+                    len,
+                    helper,
+                    &mut ctx.unifier,
+                    &ctx.top_level.definitions.read(),
+                    &ctx.primitives,
+                )?
+                .unwrap();
+            let ty = ctx.get_llvm_type(ty);
+            let arr_ty = ctx.ctx.struct_type(
+                &[
+                    ctx.ctx.i32_type().into(),
+                    ty.ptr_type(AddressSpace::Generic).into(),
+                ],
+                false,
+            );
+
+            {
+                let mut global_value_ids = self.global_value_ids.lock();
+                if global_value_ids.contains(&id) {
+                    let global = ctx.module.get_global(&id_str).unwrap_or_else(|| {
+                        ctx.module
+                            .add_global(arr_ty, Some(AddressSpace::Generic), &id_str)
+                    });
+                    return Ok(Some(global.as_pointer_value().into()));
+                } else {
+                    global_value_ids.insert(id);
+                }
+            }
+
+            let arr: Result<Option<Vec<_>>, _> = (0..len)
+                .map(|i| {
+                    obj.get_item(i)
+                        .and_then(|elem| self.get_obj_value(elem, helper, ctx))
+                })
+                .collect();
+            let arr = arr?.unwrap();
+
+            let arr_global = ctx.module.add_global(
+                ty.array_type(len as u32),
+                Some(AddressSpace::Generic),
+                &(id_str.clone() + "_"),
+            );
+            let arr: BasicValueEnum = if ty.is_int_type() {
+                let arr: Vec<_> = arr
+                    .into_iter()
+                    .map(BasicValueEnum::into_int_value)
+                    .collect();
+                ty.into_int_type().const_array(&arr)
+            } else if ty.is_float_type() {
+                let arr: Vec<_> = arr
+                    .into_iter()
+                    .map(BasicValueEnum::into_float_value)
+                    .collect();
+                ty.into_float_type().const_array(&arr)
+            } else if ty.is_array_type() {
+                let arr: Vec<_> = arr
+                    .into_iter()
+                    .map(BasicValueEnum::into_array_value)
+                    .collect();
+                ty.into_array_type().const_array(&arr)
+            } else if ty.is_struct_type() {
+                let arr: Vec<_> = arr
+                    .into_iter()
+                    .map(BasicValueEnum::into_struct_value)
+                    .collect();
+                ty.into_struct_type().const_array(&arr)
+            } else if ty.is_pointer_type() {
+                let arr: Vec<_> = arr
+                    .into_iter()
+                    .map(BasicValueEnum::into_pointer_value)
+                    .collect();
+                ty.into_pointer_type().const_array(&arr)
+            } else {
+                unreachable!()
+            }
+            .into();
+            arr_global.set_initializer(&arr);
+
+            let val = arr_ty.const_named_struct(&[
+                ctx.ctx.i32_type().const_int(len as u64, false).into(),
+                arr_global
+                    .as_pointer_value()
+                    .const_cast(ty.ptr_type(AddressSpace::Generic))
+                    .into(),
+            ]);
+
+            let global = ctx
+                .module
+                .add_global(arr_ty, Some(AddressSpace::Generic), &id_str);
+            global.set_initializer(&val);
+
+            Ok(Some(global.as_pointer_value().into()))
+        } else if ty_id == self.primitive_ids.tuple {
+            let id: u64 = helper.id_fn.call1((obj,))?.extract()?;
+            let id_str = id.to_string();
+            let elements: &PyTuple = obj.cast_as()?;
+            let types: Result<Option<Vec<_>>, _> = elements
+                .iter()
+                .map(|elem| {
+                    self.get_obj_type(
+                        elem,
+                        helper,
+                        &mut ctx.unifier,
+                        &ctx.top_level.definitions.read(),
+                        &ctx.primitives,
+                    )
+                    .map(|ty| ty.map(|ty| ctx.get_llvm_type(ty)))
+                })
+                .collect();
+            let types = types?.unwrap();
+            let ty = ctx.ctx.struct_type(&types, false);
+
+            {
+                let mut global_value_ids = self.global_value_ids.lock();
+                if global_value_ids.contains(&id) {
+                    let global = ctx.module.get_global(&id_str).unwrap_or_else(|| {
+                        ctx.module
+                            .add_global(ty, Some(AddressSpace::Generic), &id_str)
+                    });
+                    return Ok(Some(global.as_pointer_value().into()));
+                } else {
+                    global_value_ids.insert(id);
+                }
+            }
+
+            let val: Result<Option<Vec<_>>, _> = elements
+                .iter()
+                .map(|elem| self.get_obj_value(elem, helper, ctx))
+                .collect();
+            let val = val?.unwrap();
+            let val = ctx.ctx.const_struct(&val, false);
+            let global = ctx
+                .module
+                .add_global(ty, Some(AddressSpace::Generic), &id_str);
+            global.set_initializer(&val);
+            Ok(Some(global.as_pointer_value().into()))
+        } else {
+            Ok(None)
+        }
+    }
 }
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+    fn get_symbol_type(
+        &self,
+        unifier: &mut Unifier,
+        defs: &[Arc<RwLock<TopLevelDef>>],
+        primitives: &PrimitiveStore,
+        str: StrRef,
+    ) -> Option<Type> {
         let mut id_to_type = self.id_to_type.lock();
         id_to_type.get(&str).cloned().or_else(|| {
             let py_id = self.name_to_pyid.get(&str);
-            let result = py_id.and_then(|id| self.pyid_to_type.read().get(&id).copied());
+            let result = py_id.and_then(|id| {
+                self.pyid_to_type.read().get(&id).copied().or_else(|| {
+                    Python::with_gil(|py| -> PyResult<Option<Type>> {
+                        let obj: &PyAny = self.module.extract(py)?;
+                        let members: &PyList = PyModule::import(py, "inspect")?
+                            .getattr("getmembers")?
+                            .call1((obj,))?
+                            .cast_as()?;
+                        let mut sym_ty = None;
+                        for member in members.iter() {
+                            let key: &str = member.get_item(0)?.extract()?;
+                            if key == str.to_string() {
+                                let builtins = PyModule::import(py, "builtins")?;
+                                let helper = PythonHelper {
+                                    id_fn: builtins.getattr("id").unwrap(),
+                                    len_fn: builtins.getattr("len").unwrap(),
+                                    type_fn: builtins.getattr("type").unwrap(),
+                                };
+                                sym_ty = self.get_obj_type(
+                                    member.get_item(1)?,
+                                    &helper,
+                                    unifier,
+                                    defs,
+                                    primitives,
+                                )?;
+                                break;
+                            }
+                        }
+                        Ok(sym_ty)
+                    })
+                    .unwrap()
+                })
+            });
             if let Some(result) = &result {
                 id_to_type.insert(str, *result);
             }
@@ -34,8 +350,35 @@ impl SymbolResolver for Resolver {
         })
     }
 
-    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
-        unimplemented!()
+    fn get_symbol_value<'ctx, 'a>(
+        &self,
+        id: StrRef,
+        ctx: &mut CodeGenContext<'ctx, 'a>,
+    ) -> Option<BasicValueEnum<'ctx>> {
+        Python::with_gil(|py| -> PyResult<Option<BasicValueEnum<'ctx>>> {
+            let obj: &PyAny = self.module.extract(py)?;
+            let members: &PyList = PyModule::import(py, "inspect")?
+                .getattr("getmembers")?
+                .call1((obj,))?
+                .cast_as()?;
+            let mut sym_value = None;
+            for member in members.iter() {
+                let key: &str = member.get_item(0)?.extract()?;
+                let val = member.get_item(1)?;
+                if key == id.to_string() {
+                    let builtins = PyModule::import(py, "builtins")?;
+                    let helper = PythonHelper {
+                        id_fn: builtins.getattr("id").unwrap(),
+                        len_fn: builtins.getattr("len").unwrap(),
+                        type_fn: builtins.getattr("type").unwrap(),
+                    };
+                    sym_value = self.get_obj_value(val, &helper, ctx)?;
+                    break;
+                }
+            }
+            Ok(sym_value)
+        })
+        .unwrap()
     }
 
     fn get_symbol_location(&self, _: StrRef) -> Option<Location> {
diff --git a/nac3core/src/codegen/expr.rs b/nac3core/src/codegen/expr.rs
index 34407bc0..b3233c1b 100644
--- a/nac3core/src/codegen/expr.rs
+++ b/nac3core/src/codegen/expr.rs
@@ -108,7 +108,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
         fun: (&FunSignature, DefinitionId),
         params: Vec<(Option<StrRef>, BasicValueEnum<'ctx>)>,
     ) -> Option<BasicValueEnum<'ctx>> {
-        let definition = self.top_level.definitions.read().get(fun.1.0).cloned().unwrap();
+        let definition = self.top_level.definitions.read().get(fun.1 .0).cloned().unwrap();
         let mut task = None;
         let key = self.get_subst_key(obj.map(|a| a.0), fun.0, None);
         let symbol = {
@@ -283,7 +283,8 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                 } else {
                     unreachable!();
                 };
-                ty.const_int(v.try_into().unwrap(), false).into()
+                let val: i64 = v.try_into().unwrap();
+                ty.const_int(val as u64, false).into()
             }
             Constant::Float(v) => {
                 assert!(self.unifier.unioned(ty, self.primitives.float));
@@ -386,8 +387,13 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                 self.gen_const(value, ty)
             }
             ExprKind::Name { id, .. } => {
-                let ptr = self.var_assignment.get(id).unwrap();
-                self.builder.build_load(*ptr, "load")
+                let ptr = self.var_assignment.get(id);
+                if let Some(ptr) = ptr {
+                    self.builder.build_load(*ptr, "load")
+                } else {
+                    let resolver = self.resolver.clone();
+                    resolver.get_symbol_value(*id, self).unwrap()
+                }
             }
             ExprKind::List { elts, .. } => {
                 // this shall be optimized later for constant primitive lists...
@@ -647,10 +653,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                 let mut params =
                     args.iter().map(|arg| (None, self.gen_expr(arg).unwrap())).collect_vec();
                 let kw_iter = keywords.iter().map(|kw| {
-                    (
-                        Some(*kw.node.arg.as_ref().unwrap()),
-                        self.gen_expr(&kw.node.value).unwrap(),
-                    )
+                    (Some(*kw.node.arg.as_ref().unwrap()), self.gen_expr(&kw.node.value).unwrap())
                 });
                 params.extend(kw_iter);
                 let call = self.calls.get(&expr.location.into());
diff --git a/nac3core/src/codegen/test.rs b/nac3core/src/codegen/test.rs
index 3f34c664..2c7bad40 100644
--- a/nac3core/src/codegen/test.rs
+++ b/nac3core/src/codegen/test.rs
@@ -1,7 +1,7 @@
 use crate::{
-    codegen::{CodeGenTask, WithCall, WorkerRegistry},
+    codegen::{CodeGenTask, WithCall, WorkerRegistry, CodeGenContext},
     location::Location,
-    symbol_resolver::{SymbolResolver, SymbolValue},
+    symbol_resolver::SymbolResolver,
     toplevel::{
         composer::TopLevelComposer, DefinitionId, FunInstance, TopLevelContext, TopLevelDef,
     },
@@ -11,6 +11,7 @@ use crate::{
     },
 };
 use indoc::indoc;
+use inkwell::values::BasicValueEnum;
 use parking_lot::RwLock;
 use rustpython_parser::{
     ast::{fold::Fold, StrRef},
@@ -33,11 +34,11 @@ impl Resolver {
 }
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &[Arc<RwLock<TopLevelDef>>], _: &PrimitiveStore, str: StrRef) -> Option<Type> {
         self.id_to_type.get(&str).cloned()
     }
 
-    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
+    fn get_symbol_value<'ctx, 'a>(&self, _: StrRef, _: &mut CodeGenContext<'ctx, 'a>) -> Option<BasicValueEnum<'ctx>> {
         unimplemented!()
     }
 
diff --git a/nac3core/src/symbol_resolver.rs b/nac3core/src/symbol_resolver.rs
index d657e4e9..958757af 100644
--- a/nac3core/src/symbol_resolver.rs
+++ b/nac3core/src/symbol_resolver.rs
@@ -2,7 +2,7 @@ use std::collections::HashMap;
 use std::fmt::Debug;
 use std::{cell::RefCell, sync::Arc};
 
-use crate::toplevel::{DefinitionId, TopLevelDef};
+use crate::{codegen::CodeGenContext, toplevel::{DefinitionId, TopLevelDef}};
 use crate::typecheck::{
     type_inferencer::PrimitiveStore,
     typedef::{Type, Unifier},
@@ -11,6 +11,7 @@ use crate::{location::Location, typecheck::typedef::TypeEnum};
 use itertools::{chain, izip};
 use parking_lot::RwLock;
 use rustpython_parser::ast::{Expr, StrRef};
+use inkwell::values::BasicValueEnum;
 
 #[derive(Clone, PartialEq)]
 pub enum SymbolValue {
@@ -28,12 +29,13 @@ pub trait SymbolResolver {
     fn get_symbol_type(
         &self,
         unifier: &mut Unifier,
+        top_level_defs: &[Arc<RwLock<TopLevelDef>>],
         primitives: &PrimitiveStore,
         str: StrRef,
     ) -> Option<Type>;
     // get the top-level definition of identifiers
     fn get_identifier_def(&self, str: StrRef) -> Option<DefinitionId>;
-    fn get_symbol_value(&self, str: StrRef) -> Option<SymbolValue>;
+    fn get_symbol_value<'ctx, 'a>(&self, str: StrRef, ctx: &mut CodeGenContext<'ctx, 'a>) -> Option<BasicValueEnum<'ctx>>;
     fn get_symbol_location(&self, str: StrRef) -> Option<Location>;
     // handle function call etc.
 }
@@ -113,7 +115,7 @@ pub fn parse_type_annotation<T>(
                 } else {
                     // it could be a type variable
                     let ty = resolver
-                        .get_symbol_type(unifier, primitives, *id)
+                        .get_symbol_type(unifier, top_level_defs, primitives, *id)
                         .ok_or_else(|| "unknown type variable name".to_owned())?;
                     if let TypeEnum::TVar { .. } = &*unifier.get_ty(ty) {
                         Ok(ty)
diff --git a/nac3core/src/toplevel/test.rs b/nac3core/src/toplevel/test.rs
index a53bed77..e652236b 100644
--- a/nac3core/src/toplevel/test.rs
+++ b/nac3core/src/toplevel/test.rs
@@ -1,6 +1,7 @@
 use crate::{
+    codegen::CodeGenContext,
     location::Location,
-    symbol_resolver::{SymbolResolver, SymbolValue},
+    symbol_resolver::SymbolResolver,
     toplevel::DefinitionId,
     typecheck::{
         type_inferencer::PrimitiveStore,
@@ -34,7 +35,7 @@ impl ResolverInternal {
 struct Resolver(Arc<ResolverInternal>);
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &[Arc<RwLock<TopLevelDef>>], _: &PrimitiveStore, str: StrRef) -> Option<Type> {
         let ret = self.0.id_to_type.lock().get(&str).cloned();
         if ret.is_none() {
             // println!("unknown here resolver {}", str);
@@ -42,7 +43,11 @@ impl SymbolResolver for Resolver {
         ret
     }
 
-    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
+    fn get_symbol_value<'ctx, 'a>(
+        &self,
+        _: StrRef,
+        _: &mut CodeGenContext<'ctx, 'a>,
+    ) -> Option<BasicValueEnum<'ctx>> {
         unimplemented!()
     }
 
diff --git a/nac3core/src/toplevel/type_annotation.rs b/nac3core/src/toplevel/type_annotation.rs
index 6d4d6f0d..7f33e823 100644
--- a/nac3core/src/toplevel/type_annotation.rs
+++ b/nac3core/src/toplevel/type_annotation.rs
@@ -62,7 +62,7 @@ pub fn parse_ast_to_type_annotation_kinds<T>(
                     ));
                 }
                 Ok(TypeAnnotation::CustomClassKind { id: obj_id, params: vec![] })
-            } else if let Some(ty) = resolver.get_symbol_type(unifier, primitives, *id) {
+            } else if let Some(ty) = resolver.get_symbol_type(unifier, top_level_defs, primitives, *id) {
                 if let TypeEnum::TVar { .. } = unifier.get_ty(ty).as_ref() {
                     Ok(TypeAnnotation::TypeVarKind(ty))
                 } else {
diff --git a/nac3core/src/typecheck/function_check.rs b/nac3core/src/typecheck/function_check.rs
index fce0589b..c66bacfe 100644
--- a/nac3core/src/typecheck/function_check.rs
+++ b/nac3core/src/typecheck/function_check.rs
@@ -57,7 +57,17 @@ impl<'a> Inferencer<'a> {
         match &expr.node {
             ExprKind::Name { id, .. } => {
                 if !defined_identifiers.contains(id) {
-                    if self.function_data.resolver.get_identifier_def(*id).is_some() {
+                    if self
+                        .function_data
+                        .resolver
+                        .get_symbol_type(
+                            self.unifier,
+                            &self.top_level.definitions.read(),
+                            self.primitives,
+                            *id,
+                        )
+                        .is_some()
+                    {
                         defined_identifiers.insert(*id);
                     } else {
                         return Err(format!(
diff --git a/nac3core/src/typecheck/type_inferencer/mod.rs b/nac3core/src/typecheck/type_inferencer/mod.rs
index af7008ad..eb54ce9c 100644
--- a/nac3core/src/typecheck/type_inferencer/mod.rs
+++ b/nac3core/src/typecheck/type_inferencer/mod.rs
@@ -111,32 +111,40 @@ impl<'a> fold::Fold<()> for Inferencer<'a> {
                     if let ast::StmtKind::Assign { targets, value, .. } = node.node {
                         let value = self.fold_expr(*value)?;
                         let value_ty = value.custom.unwrap();
-                        let targets: Result<Vec<_>, _> = targets.into_iter().map(|target| {
-                            if let ast::ExprKind::Name { id, ctx } = target.node {
-                                self.defined_identifiers.insert(id);
-                                let target_ty = if let Some(ty) = self.variable_mapping.get(&id) {
-                                    *ty
+                        let targets: Result<Vec<_>, _> = targets
+                            .into_iter()
+                            .map(|target| {
+                                if let ast::ExprKind::Name { id, ctx } = target.node {
+                                    self.defined_identifiers.insert(id);
+                                    let target_ty = if let Some(ty) = self.variable_mapping.get(&id)
+                                    {
+                                        *ty
+                                    } else {
+                                        let unifier = &mut self.unifier;
+                                        self.function_data
+                                            .resolver
+                                            .get_symbol_type(
+                                                unifier,
+                                                &self.top_level.definitions.read(),
+                                                self.primitives,
+                                                id,
+                                            )
+                                            .unwrap_or_else(|| {
+                                                self.variable_mapping.insert(id, value_ty);
+                                                value_ty
+                                            })
+                                    };
+                                    let location = target.location;
+                                    self.unifier.unify(value_ty, target_ty).map(|_| Located {
+                                        location,
+                                        node: ast::ExprKind::Name { id, ctx },
+                                        custom: Some(target_ty),
+                                    })
                                 } else {
-                                    let unifier = &mut self.unifier;
-                                    self
-                                        .function_data
-                                        .resolver
-                                        .get_symbol_type(unifier, self.primitives, id)
-                                        .unwrap_or_else(|| {
-                                            self.variable_mapping.insert(id, value_ty);
-                                            value_ty
-                                        })
-                                };
-                                let location = target.location;
-                                self.unifier.unify(value_ty, target_ty).map(|_| Located {
-                                    location,
-                                    node: ast::ExprKind::Name { id, ctx },
-                                    custom: Some(target_ty)
-                                })
-                            } else {
-                                unreachable!()
-                            }
-                        }).collect();
+                                    unreachable!()
+                                }
+                            })
+                            .collect();
                         let targets = targets?;
                         return Ok(Located {
                             location: node.location,
@@ -145,7 +153,7 @@ impl<'a> fold::Fold<()> for Inferencer<'a> {
                                 value: Box::new(value),
                                 type_comment: None,
                             },
-                            custom: None
+                            custom: None,
                         });
                     } else {
                         unreachable!()
@@ -207,7 +215,17 @@ impl<'a> fold::Fold<()> for Inferencer<'a> {
             ast::ExprKind::Constant { value, .. } => Some(self.infer_constant(value)?),
             ast::ExprKind::Name { id, .. } => {
                 if !self.defined_identifiers.contains(id) {
-                    if self.function_data.resolver.get_identifier_def(*id).is_some() {
+                    if self
+                        .function_data
+                        .resolver
+                        .get_symbol_type(
+                            self.unifier,
+                            &self.top_level.definitions.read(),
+                            self.primitives,
+                            *id,
+                        )
+                        .is_some()
+                    {
                         self.defined_identifiers.insert(*id);
                     } else {
                         return Err(format!(
@@ -359,11 +377,8 @@ impl<'a> Inferencer<'a> {
                 defined_identifiers.insert(*name);
             }
         }
-        let fn_args: Vec<_> = args
-            .args
-            .iter()
-            .map(|v| (v.node.arg, self.unifier.get_fresh_var().0))
-            .collect();
+        let fn_args: Vec<_> =
+            args.args.iter().map(|v| (v.node.arg, self.unifier.get_fresh_var().0)).collect();
         let mut variable_mapping = self.variable_mapping.clone();
         variable_mapping.extend(fn_args.iter().cloned());
         let ret = self.unifier.get_fresh_var().0;
@@ -596,7 +611,7 @@ impl<'a> Inferencer<'a> {
             Ok(self
                 .function_data
                 .resolver
-                .get_symbol_type(unifier, self.primitives, id)
+                .get_symbol_type(unifier, &self.top_level.definitions.read(), self.primitives, id)
                 .unwrap_or_else(|| {
                     let ty = unifier.get_fresh_var().0;
                     variable_mapping.insert(id, ty);
diff --git a/nac3core/src/typecheck/type_inferencer/test.rs b/nac3core/src/typecheck/type_inferencer/test.rs
index 24dc2df1..aea6a326 100644
--- a/nac3core/src/typecheck/type_inferencer/test.rs
+++ b/nac3core/src/typecheck/type_inferencer/test.rs
@@ -1,11 +1,12 @@
 use super::super::typedef::*;
 use super::*;
-use crate::symbol_resolver::*;
 use crate::{
+    codegen::CodeGenContext,
     location::Location,
     toplevel::{DefinitionId, TopLevelDef},
 };
 use indoc::indoc;
+use inkwell::values::BasicValueEnum;
 use itertools::zip;
 use parking_lot::RwLock;
 use rustpython_parser::parser::parse_program;
@@ -18,11 +19,15 @@ struct Resolver {
 }
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &[Arc<RwLock<TopLevelDef>>], _: &PrimitiveStore, str: StrRef) -> Option<Type> {
         self.id_to_type.get(&str).cloned()
     }
 
-    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
+    fn get_symbol_value<'ctx, 'a>(
+        &self,
+        _: StrRef,
+        _: &mut CodeGenContext<'ctx, 'a>,
+    ) -> Option<BasicValueEnum<'ctx>> {
         unimplemented!()
     }
 
@@ -278,7 +283,7 @@ impl TestEnvironment {
         let top_level = TopLevelContext {
             definitions: Arc::new(top_level_defs.into()),
             unifiers: Default::default(),
-            personality_symbol: None
+            personality_symbol: None,
         };
 
         let resolver = Arc::new(Box::new(Resolver {
diff --git a/nac3standalone/src/basic_symbol_resolver.rs b/nac3standalone/src/basic_symbol_resolver.rs
index 92f0d0c5..4d42cc37 100644
--- a/nac3standalone/src/basic_symbol_resolver.rs
+++ b/nac3standalone/src/basic_symbol_resolver.rs
@@ -1,13 +1,9 @@
-use nac3core::{
-    location::Location,
-    symbol_resolver::{SymbolResolver, SymbolValue},
-    toplevel::DefinitionId,
-    typecheck::{
+use inkwell::values::BasicValueEnum;
+use nac3core::{codegen::CodeGenContext, location::Location, symbol_resolver::{SymbolResolver, SymbolValue}, toplevel::{DefinitionId, TopLevelDef}, typecheck::{
         type_inferencer::PrimitiveStore,
         typedef::{Type, Unifier},
-    },
-};
-use parking_lot::Mutex;
+    }};
+use parking_lot::{Mutex, RwLock};
 use rustpython_parser::ast::StrRef;
 use std::{collections::HashMap, sync::Arc};
 
@@ -30,7 +26,7 @@ impl ResolverInternal {
 pub struct Resolver(pub Arc<ResolverInternal>);
 
 impl SymbolResolver for Resolver {
-    fn get_symbol_type(&self, _: &mut Unifier, _: &PrimitiveStore, str: StrRef) -> Option<Type> {
+    fn get_symbol_type(&self, _: &mut Unifier, _: &[Arc<RwLock<TopLevelDef>>], _: &PrimitiveStore, str: StrRef) -> Option<Type> {
         let ret = self.0.id_to_type.lock().get(&str).cloned();
         if ret.is_none() {
             // println!("unknown here resolver {}", str);
@@ -38,7 +34,7 @@ impl SymbolResolver for Resolver {
         ret
     }
 
-    fn get_symbol_value(&self, _: StrRef) -> Option<SymbolValue> {
+    fn get_symbol_value<'ctx, 'a>(&self, _: StrRef, _: &mut CodeGenContext<'ctx, 'a>) -> Option<BasicValueEnum<'ctx>> {
         unimplemented!()
     }