diff --git a/src/ast_compiler.rs b/src/ast_compiler.rs
index c09c038..7df9d0f 100644
--- a/src/ast_compiler.rs
+++ b/src/ast_compiler.rs
@@ -228,6 +228,9 @@ impl AstCompiler {
     }
 
     fn let_declaration(&mut self) -> Result<Statement, CompilerError> {
+        if self.peek().token_type.is_type(){
+            return Err(CompilerError::KeywordNotAllowedAsIdentifier(self.peek().token_type))
+        }
         let name_token = self.consume(Identifier, Expected("variable name."))?;
 
         let declared_type = if self.check(Colon) {
diff --git a/src/bytecode_compiler.rs b/src/bytecode_compiler.rs
index 2556be0..044fcd6 100644
--- a/src/bytecode_compiler.rs
+++ b/src/bytecode_compiler.rs
@@ -1,16 +1,22 @@
 use crate::ast_compiler::{Expression, Function, Statement};
 use crate::chunk::Chunk;
+use crate::errors::CompilerError;
 use crate::tokens::TokenType;
 use crate::value::Value;
-use crate::vm::{OP_ADD, OP_AND, OP_BITAND, OP_BITOR, OP_BITXOR, OP_CALL, OP_CONSTANT, OP_DEF_BOOL, OP_DEF_CHAR, OP_DEF_DATE, OP_DEF_F32, OP_DEF_F64, OP_DEF_I32, OP_DEF_I64, OP_DEF_LIST, OP_DEF_MAP, OP_DEF_STRING, OP_DEF_STRUCT, OP_DEFINE, OP_DIVIDE, OP_EQUAL, OP_GET, OP_GREATER, OP_GREATER_EQUAL, OP_LESS, OP_LESS_EQUAL, OP_MULTIPLY, OP_NEGATE, OP_NOT, OP_OR, OP_PRINT, OP_RETURN, OP_SHL, OP_SHR, OP_SUBTRACT, OP_DEF_U32};
+use crate::vm::{
+    OP_ADD, OP_AND, OP_ASSIGN, OP_BITAND, OP_BITOR, OP_BITXOR, OP_CALL, OP_CONSTANT, OP_DEF_BOOL,
+    OP_DEF_CHAR, OP_DEF_DATE, OP_DEF_F32, OP_DEF_F64, OP_DEF_I32, OP_DEF_I64, OP_DEF_LIST,
+    OP_DEF_MAP, OP_DEF_STRING, OP_DEF_STRUCT, OP_DEF_U32, OP_DEFINE, OP_DIVIDE, OP_EQUAL, OP_GET,
+    OP_GREATER, OP_GREATER_EQUAL, OP_LESS, OP_LESS_EQUAL, OP_MULTIPLY, OP_NEGATE, OP_NOT, OP_OR,
+    OP_PRINT, OP_RETURN, OP_SHL, OP_SHR, OP_SUBTRACT,
+};
 use std::collections::HashMap;
-use crate::errors::CompilerError;
 
 pub fn compile(
     namespace: Option<&str>,
     ast: &Vec<Statement>,
     registry: &mut HashMap<String, Chunk>,
-) -> Result<(),CompilerError> {
+) -> Result<(), CompilerError> {
     compile_name(ast, namespace, registry)
 }
 
@@ -22,9 +28,10 @@ pub(crate) fn compile_function(
     let mut compiler = Compiler::new(&function.name.lexeme);
     for parm in &function.parameters {
         let name = parm.name.lexeme.clone();
-        let name_index = compiler.chunk.add_constant(Value::String(name.clone()));
-        compiler.vars.insert(name, name_index);
-        compiler.emit_bytes(OP_DEFINE, name_index as u16);
+        let var_index = compiler.chunk.add_var(&parm.var_type, &parm.name.lexeme);
+
+        compiler.vars.insert(name, var_index);
+        // compiler.emit_bytes(OP_DEFINE, name_index as u16);
     }
 
     Ok(compiler.compile(&function.body, registry, namespace)?)
@@ -34,11 +41,11 @@ pub(crate) fn compile_name(
     ast: &Vec<Statement>,
     namespace: Option<&str>,
     registry: &mut HashMap<String, Chunk>,
-) -> Result<(),CompilerError> {
-    let name=namespace.unwrap_or("main");
+) -> Result<(), CompilerError> {
+    let name = namespace.unwrap_or("main");
     let compiler = Compiler::new(name);
     let chunk = compiler.compile(ast, registry, name)?;
-    let qname = if let Some(namespace) = namespace{
+    let qname = if let Some(namespace) = namespace {
         format!("{}.{}", namespace, "main")
     } else {
         "main".to_string()
@@ -70,17 +77,6 @@ impl Compiler {
         registry: &mut HashMap<String, Chunk>,
         namespace: &str,
     ) -> Result<Chunk, CompilerError> {
-        //TODO can likely be removed
-        for statement in ast {
-            if let Statement::FunctionStmt { function } = statement {
-                self.emit_constant(Value::String(format!(
-                    "{}.{}",
-                    namespace,
-                    function.name.lexeme.clone()
-                )));
-            }
-        }
-
         for statement in ast {
             self.compile_statement(statement, registry, namespace)?;
         }
@@ -102,10 +98,10 @@ impl Compiler {
                 var_type,
                 initializer,
             } => {
-                let name_index = self.chunk.add_constant(Value::String(name.lexeme.clone()));
+                let name_index = self.chunk.add_var(var_type, &name.lexeme);
                 self.vars.insert(name.lexeme.clone(), name_index);
                 self.compile_expression(namespace, initializer, registry)?;
-                self.define_variable(var_type, name_index, &initializer)?;
+                self.emit_bytes(OP_ASSIGN, name_index as u16);
             }
             Statement::PrintStmt { value } => {
                 self.compile_expression(namespace, value, registry)?;
@@ -116,7 +112,7 @@ impl Compiler {
             }
             Statement::FunctionStmt { function } => {
                 let function_name = function.name.lexeme.clone();
-                self.emit_constant(Value::String(function_name.clone()));
+                // self.emit_constant(Value::String(function_name.clone()));
                 let compiled_function = compile_function(function, registry, namespace)?;
                 registry.insert(
                     format!("{}.{}", self.chunk.name, function_name),
@@ -140,7 +136,7 @@ impl Compiler {
             Expression::FunctionCall {
                 name, arguments, ..
             } => {
-                let qname=format!("{}.{}", namespace, name);
+                let qname = format!("{}.{}", namespace, name);
                 let name_index = self
                     .chunk
                     .find_constant(&qname)
@@ -163,12 +159,14 @@ impl Compiler {
                 for expr in values {
                     self.compile_expression(namespace, expr, registry)?;
                 }
+                self.emit_bytes(OP_DEF_LIST, values.len() as u16);
             }
             Expression::Map { entries, .. } => {
                 for (key, value) in entries {
                     self.compile_expression(namespace, key, registry)?;
                     self.compile_expression(namespace, value, registry)?;
                 }
+                self.emit_bytes(OP_DEF_MAP, entries.len() as u16);
             }
             Expression::Grouping { expression, .. } => {
                 self.compile_expression(namespace, expression, registry)?
@@ -219,42 +217,6 @@ impl Compiler {
         Ok(())
     }
 
-    fn define_variable(
-        &mut self,
-        var_type: &TokenType,
-        name_index: usize,
-        initializer: &Expression,
-    ) -> Result<(), CompilerError> {
-        let def_op = match var_type {
-            TokenType::I32 => OP_DEF_I32,
-            TokenType::I64 => OP_DEF_I64,
-            TokenType::U32 => OP_DEF_U32,
-            TokenType::U64 => OP_DEF_I64,
-            TokenType::F32 => OP_DEF_F32,
-            TokenType::F64 => OP_DEF_F64,
-            TokenType::Date => OP_DEF_DATE,
-            TokenType::StringType => OP_DEF_STRING,
-            TokenType::Char => OP_DEF_CHAR,
-            TokenType::Bool => OP_DEF_BOOL,
-            TokenType::ListType => OP_DEF_LIST,
-            TokenType::MapType => OP_DEF_MAP,
-            TokenType::Object => OP_DEF_STRUCT,
-            _ => unimplemented!("{}", var_type),
-        };
-
-        self.emit_bytes(def_op, name_index as u16);
-        match initializer {
-            Expression::List { values, .. } => {
-                self.emit_byte(values.len() as u16);
-            }
-            Expression::Map { entries, .. } => {
-                self.emit_byte(entries.len() as u16);
-            }
-            _ => {}
-        }
-        Ok(())
-    }
-
     fn emit_byte(&mut self, byte: u16) {
         self.chunk.add(byte, self.current_line);
     }
diff --git a/src/chunk.rs b/src/chunk.rs
index 9d0d05b..cb19807 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use crate::ast_compiler::Parameter;
+use crate::tokens::TokenType;
 use crate::value::Value;
 use crate::vm::{
     OP_ADD, OP_BITAND, OP_BITOR, OP_BITXOR, OP_CALL, OP_CONSTANT, OP_DEF_BOOL, OP_DEF_F32,
@@ -14,7 +15,8 @@ pub struct Chunk {
     pub code: Vec<u16>,
     pub constants: Vec<Value>,
     lines: Vec<usize>,
-    object_defs: HashMap<String, Vec<Parameter>>
+    object_defs: HashMap<String, Vec<Parameter>>,
+    pub vars: Vec<(TokenType, String)>
 }
 
 impl Chunk {
@@ -38,6 +40,7 @@ impl Chunk {
             constants: vec![],
             lines: vec![],
             object_defs: HashMap::new(),
+            vars: vec![]
         }
     }
 
@@ -51,6 +54,11 @@ impl Chunk {
         self.constants.len() - 1
     }
 
+    pub(crate) fn add_var(&mut self, var_type: &TokenType, name: &str) -> usize {
+        self.vars.push((var_type.clone(), name.to_string()));
+        self.vars.len() - 1
+    }
+
     pub (crate) fn add_object_def(&mut self, name: &str, fields: &[Parameter]){
         self.object_defs.insert(name.to_string(), fields.to_vec());
     }
diff --git a/src/compiler_tests.rs b/src/compiler_tests.rs
index 966f32f..3fba686 100644
--- a/src/compiler_tests.rs
+++ b/src/compiler_tests.rs
@@ -29,19 +29,19 @@ mod tests {
     }
 
     #[test]
-    fn let_infer_type() {
+    fn infer_type() {
         assert_eq!(run(r#"let a=1
 a"#), Ok(Value::I64(1)));
     }
 
     #[test]
-    fn let_u32() {
+    fn define_u32() {
         assert_eq!(run(r#"let a:u32=1
 a"#), Ok(Value::U32(1)));
     }
 
     #[test]
-    fn let_char() {
+    fn define_char() {
         assert_eq!(
             run(r#"let a:char='a'
 a"#),
@@ -50,7 +50,7 @@ a"#),
     }
 
     #[test]
-    fn let_u32_invalid_value_negative() {
+    fn define_u32_invalid_value_negative() {
         let r = compile("let a:u32=-1");
         assert!(r.is_err());
         if let Err(e) = &r {
@@ -62,7 +62,7 @@ a"#),
     }
 
     #[test]
-    fn let_u64_invalid_value_negative() {
+    fn define_u64_invalid_value_negative() {
         let r = compile("let a:u64=-1");
         assert!(r.is_err());
         if let Err(e) = &r {
@@ -97,7 +97,7 @@ add_hello("world")"#,),
     }
 
     #[test]
-    fn object_definition() {
+    fn define_object() {
         let r = compile(
             r#"
 object Person:
@@ -120,7 +120,7 @@ object Person:
     //     }
 
     #[test]
-    fn let_map() {
+    fn literal_map() {
         let result = run(r#"{"name": "Dent", "age": 40 }"#);
         assert!(result.is_ok());
         let result = result.unwrap();
@@ -131,8 +131,29 @@ object Person:
             );
             assert_eq!(
                 map.get(&Value::String("age".to_string())).unwrap(),
-                &Value::I32(40)
+                &Value::I64(40)
             );
         }
     }
+
+    #[test]
+    fn define_map() {
+        let result = run(r#"let m = {"name": "Dent"}
+m"#);
+
+        let result = result.unwrap();
+        if let Value::Map(map) = result {
+            assert_eq!(
+                map.get(&Value::String("name".to_string())).unwrap(),
+                &Value::String("Dent".to_string())
+            );
+        }
+    }
+
+    #[test]
+    fn keyword_error(){
+        let result = run(r#"let map = {"name": "Dent"}"#);
+        assert!(result.is_err());
+        assert_eq!("'map' is a keyword. You cannot use it as an identifier",result.unwrap_err().to_string());
+    }
 }
diff --git a/src/errors.rs b/src/errors.rs
index 0fa85e8..df13ea4 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -1,5 +1,5 @@
-use thiserror::Error;
 use crate::tokens::{Token, TokenType};
+use thiserror::Error;
 
 #[derive(Error, Debug, PartialEq)]
 pub enum Error {
@@ -11,7 +11,6 @@ pub enum Error {
     Platform(String),
 }
 
-
 #[derive(Error, Debug, PartialEq)]
 pub enum CompilerError {
     #[error("Compilation failed")]
@@ -21,7 +20,7 @@ pub enum CompilerError {
     #[error("Expected {0}")]
     Expected(&'static str),
     #[error("unexpected indent level {0} vs expected {1}")]
-    UnexpectedIndent(usize,usize),
+    UnexpectedIndent(usize, usize),
     #[error("Type mismatch at line {0}: {1}")]
     TypeError(usize, Box<CompilerError>),
     #[error("Uninitialized variables are not allowed.")]
@@ -39,7 +38,9 @@ pub enum CompilerError {
     #[error("Illegal char length for {0} at line {1}")]
     IllegalCharLength(String, usize),
     #[error("Unexpected type {0}")]
-    UnexpectedType(TokenType)
+    UnexpectedType(TokenType),
+    #[error("'{0}' is a keyword. You cannot use it as an identifier")]
+    KeywordNotAllowedAsIdentifier(TokenType),
 }
 
 #[derive(Error, Debug, PartialEq)]
@@ -58,4 +59,6 @@ pub enum ValueError {
     CannotAnd(&'static str),
     #[error("{0}")]
     Some(&'static str),
-}
\ No newline at end of file
+    #[error("Illegal cast")]
+    IllegalCast,
+}
diff --git a/src/value.rs b/src/value.rs
index 30f4dc4..a3ec450 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -1,10 +1,10 @@
+use crate::errors::ValueError;
 use chrono::{DateTime, Utc};
 use std::cmp::Ordering;
 use std::collections::HashMap;
 use std::fmt::{Display, Formatter};
 use std::hash::{Hash, Hasher};
 use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Neg, Not, Shl, Shr, Sub};
-use crate::errors::ValueError;
 
 #[derive(Debug, Clone)]
 pub struct Object {
@@ -32,6 +32,56 @@ pub enum Value {
     Void,
 }
 
+impl Value {
+    pub fn cast_u32(self) -> Result<Self, ValueError> {
+        match self {
+            Value::U32(v) => Ok(Value::U32(v)),
+            Value::U64(v) => Ok(Value::U32(v as u32)),
+            Value::I32(v) => Ok(Value::U32(v as u32)),
+            Value::I64(v) => Ok(Value::U32(v as u32)),
+            Value::F32(v) => Ok(Value::U32(v as u32)),
+            Value::F64(v) => Ok(Value::U32(v as u32)),
+            _ => Err(ValueError::IllegalCast),
+        }
+    }
+
+    pub fn cast_u64(self) -> Result<Self, ValueError> {
+        match self {
+            Value::U32(v) => Ok(Value::U64(v as u64)),
+            Value::U64(v) => Ok(Value::U64(v)),
+            Value::I32(v) => Ok(Value::U64(v as u64)),
+            Value::I64(v) => Ok(Value::U64(v as u64)),
+            Value::F32(v) => Ok(Value::U64(v as u64)),
+            Value::F64(v) => Ok(Value::U64(v as u64)),
+            _ => Err(ValueError::IllegalCast),
+        }
+    }
+
+    pub fn cast_i32(self) -> Result<Self, ValueError> {
+        match self {
+            Value::U32(v) => Ok(Value::I32(v as i32)),
+            Value::U64(v) => Ok(Value::I32(v as i32)),
+            Value::I32(v) => Ok(Value::I32(v)),
+            Value::I64(v) => Ok(Value::I32(v as i32)),
+            Value::F32(v) => Ok(Value::I32(v as i32)),
+            Value::F64(v) => Ok(Value::I32(v as i32)),
+            _ => Err(ValueError::IllegalCast),
+        }
+    }
+
+    pub fn cast_f32(self) -> Result<Self, ValueError> {
+        match self {
+            Value::U32(v) => Ok(Value::F32(v as f32)),
+            Value::U64(v) => Ok(Value::F32(v as f32)),
+            Value::I32(v) => Ok(Value::F32(v as f32)),
+            Value::I64(v) => Ok(Value::F32(v as f32)),
+            Value::F32(v) => Ok(Value::F32(v)),
+            Value::F64(v) => Ok(Value::F32(v as f32)),
+            _ => Err(ValueError::IllegalCast),
+        }
+    }
+}
+
 impl Into<Value> for i32 {
     fn into(self) -> Value {
         Value::I32(self)
diff --git a/src/vm.rs b/src/vm.rs
index 6f7a1d3..519831d 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -4,6 +4,7 @@ use crate::errors::{RuntimeError, ValueError};
 use crate::value::Value;
 use std::collections::HashMap;
 use tracing::debug;
+use crate::tokens::TokenType;
 
 macro_rules! define_var {
     ($self:ident, $variant:ident, $chunk:ident) => {{
@@ -40,7 +41,7 @@ pub fn interpret(registry: &HashMap<String, Chunk>, function: &str) -> Result<Va
         error_occurred: false,
         registry,
     };
-    vm.run(&chunk, vec![])
+    vm.run(&chunk)
 }
 
 pub async fn interpret_async(registry: &HashMap<String, Chunk>, function: &str) -> Result<Value, RuntimeError> {
@@ -52,7 +53,7 @@ pub async fn interpret_async(registry: &HashMap<String, Chunk>, function: &str)
         error_occurred: false,
         registry,
     };
-    vm.run(&chunk, vec![])
+    vm.run(&chunk)
 }
 
 pub fn interpret_function(chunk: &Chunk, args: Vec<Value>) -> Result<Value, RuntimeError> {
@@ -63,14 +64,20 @@ pub fn interpret_function(chunk: &Chunk, args: Vec<Value>) -> Result<Value, Runt
         error_occurred: false,
         registry: &HashMap::new(),
     };
-    vm.run(chunk, args)
+
+    vm.run_function(chunk, args)
 }
 
 impl<'a> Vm<'a> {
-    fn run(&mut self, chunk: &Chunk, args: Vec<Value>) -> Result<Value, RuntimeError> {
-        for arg in args {
-            self.push(arg);
+    fn run_function(&mut self, chunk: &Chunk, mut args: Vec<Value>) -> Result<Value, RuntimeError> {
+        // arguments -> locals
+        for (_,name) in chunk.vars.iter() {
+            self.local_vars.insert(name.clone(), args.remove(0));
         }
+        self.run(&chunk)
+    }
+
+    fn run(&mut self, chunk: &Chunk) -> Result<Value, RuntimeError> {
         loop {
             if self.error_occurred {
                 return Err(Something);
@@ -131,64 +138,30 @@ impl<'a> Vm<'a> {
                     let value = self.pop();
                     self.local_vars.insert(name, value);
                 }
-                OP_DEF_I32 => {
-                    let name = self.read_name(chunk);
-                    let value = self.pop();
-                    let value = match value{
-                        Value::I32(v) => Value::I32(v),
-                        Value::I64(v) => Value::I32(v as i32),
-                        _ => unreachable!(),
-                    };
-                    self.local_vars.insert(name, value);
-                }
-                OP_DEF_I64 => define_var!(self, I64, chunk),
-                OP_DEF_U32 => {
-                    let name = self.read_name(chunk);
-                    let value = self.pop();
-                    let value = match value{
-                        Value::U32(v) => Value::U32(v),
-                        Value::I64(v) => Value::U32(v as u32),
-                        _ => unreachable!(),
-                    };
-                    self.local_vars.insert(name, value);
-                }
-                OP_DEF_U64 => {
-                    let name = self.read_name(chunk);
-                    let value = self.pop();
-                    let value = match value{
-                        Value::U64(v) => Value::U64(v),
-                        Value::I64(v) => Value::U64(v as u64),
-                        _ => unreachable!(),
-                    };
-                    self.local_vars.insert(name, value);
-                }
-                OP_DEF_F32 => {
-                    let name = self.read_name(chunk);
-                    let value = self.pop();
-                    let value = match value{
-                        Value::F32(v) => Value::F32(v),
-                        Value::F64(v) => Value::F32(v as f32),
-                        _ => unreachable!(),
-                    };
-                    self.local_vars.insert(name, value);
-                }
-                OP_DEF_F64 => define_var!(self, F64, chunk),
-                OP_DEF_STRING => define_var!(self, String, chunk),
-                OP_DEF_CHAR => define_var!(self, Char, chunk),
-                OP_DEF_BOOL => define_var!(self, Bool, chunk),
-                OP_DEF_DATE => define_var!(self, Date, chunk),
                 OP_DEF_LIST => {
-                    let name = self.read_name(chunk);
                     let len = self.read(chunk);
                     let mut list = vec![];
                     for _ in 0..len {
                         let value = self.pop();
                         list.push(value);
                     }
-                    self.local_vars.insert(name, Value::List(list));
+                    list.reverse();
+                    self.push(Value::List(list));
+                }
+                OP_ASSIGN=>{
+                    let index = self.read(chunk);
+                    let (var_type, name) = chunk.vars.get(index).unwrap();
+                    let value = self.pop();
+                    let value = match var_type{
+                        TokenType::U32 => value.cast_u32()?,
+                        TokenType::U64 => value.cast_u64()?,
+                        TokenType::F32 => value.cast_f32()?,
+                        TokenType::I32 => value.cast_i32()?,
+                        _ => value,
+                    };
+                    self.local_vars.insert(name.to_string(), value);
                 }
                 OP_DEF_MAP => {
-                    let name = self.read_name(chunk);
                     let len = self.read(chunk);
                     let mut map = HashMap::new();
                     for _ in 0..len {
@@ -196,12 +169,13 @@ impl<'a> Vm<'a> {
                         let key = self.pop();
                         map.insert(key, value);
                     }
-                    self.local_vars.insert(name, Value::Map(map));
+                    self.push(Value::Map(map));
                 }
                 OP_GET => {
-                    let name = self.read_name(chunk);
-                    let value = self.local_vars.get(&name).unwrap();
-                    self.push(value.clone()); // not happy
+                    let var_index = self.read(chunk);
+                    let (_,name_index)= chunk.vars.get(var_index).unwrap();
+                    let value = self.local_vars.get(name_index).unwrap();
+                    self.push(value.clone()); // not happy , take ownership, no clone
                     debug!("after get {:?}", self.stack);
                 }
                 OP_CALL => {
@@ -309,4 +283,4 @@ pub const OP_DEF_MAP: u16 = 37;
 pub const OP_DEF_STRUCT: u16 = 38;
 pub const OP_DEF_F32: u16 = 39;
 pub const OP_DEF_F64: u16 = 40;
-// pub const OP_NEW_LIST: u16 = 40;
+pub const OP_ASSIGN: u16 = 41;