diff --git a/Cargo.lock b/Cargo.lock
index 3d0ac9f..e2e573d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -114,6 +114,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c918d541ef2913577a0f9566e9ce27cb35b6df072075769e0b26cb5a554520da"
 dependencies = [
  "clap_builder",
+ "clap_derive",
 ]
 
 [[package]]
@@ -128,6 +129,18 @@ dependencies = [
  "strsim",
 ]
 
+[[package]]
+name = "clap_derive"
+version = "4.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "307bc0538d5f0f83b8248db3087aa92fe504e4691294d0c96c0eabc33f47ba47"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.50",
+]
+
 [[package]]
 name = "clap_lex"
 version = "0.7.0"
@@ -155,6 +168,16 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7a81dae078cea95a014a339291cec439d2f232ebe854a9d672b796c6afafa9b7"
 
+[[package]]
+name = "ctrlc"
+version = "3.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b467862cc8610ca6fc9a1532d7777cee0804e678ab45410897b9396495994a0b"
+dependencies = [
+ "nix",
+ "windows-sys",
+]
+
 [[package]]
 name = "diff"
 version = "0.1.13"
@@ -259,6 +282,12 @@ version = "0.14.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
 
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
 [[package]]
 name = "hermit-abi"
 version = "0.3.6"
@@ -335,6 +364,12 @@ dependencies = [
  "regex",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
 [[package]]
 name = "libc"
 version = "0.2.153"
@@ -659,6 +694,17 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5ee073c9e4cd00e28217186dbe12796d692868f432bf2e97ee73bed0c56dfa01"
 
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.50"
@@ -675,8 +721,10 @@ name = "talc-bin"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "ctrlc",
  "rustyline",
  "talc-lang",
+ "talc-std",
 ]
 
 [[package]]
@@ -685,14 +733,28 @@ version = "0.1.0"
 dependencies = [
  "lalrpop",
  "lalrpop-util",
+ "lazy_static",
  "num-complex",
  "num-rational",
  "thiserror",
 ]
 
+[[package]]
+name = "talc-macros"
+version = "0.1.0"
+dependencies = [
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "talc-std"
 version = "0.1.0"
+dependencies = [
+ "lazy_static",
+ "talc-lang",
+ "talc-macros",
+]
 
 [[package]]
 name = "term"
@@ -722,7 +784,7 @@ checksum = "a953cb265bef375dae3de6663da4d3804eee9682ea80d8e2542529b73c531c81"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.50",
 ]
 
 [[package]]
@@ -798,7 +860,7 @@ version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
 dependencies = [
- "windows-targets 0.52.0",
+ "windows-targets 0.52.3",
 ]
 
 [[package]]
@@ -818,17 +880,17 @@ dependencies = [
 
 [[package]]
 name = "windows-targets"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a18201040b24831fbb9e4eb208f8892e1f50a37feb53cc7ff887feb8f50e7cd"
+checksum = "d380ba1dc7187569a8a9e91ed34b8ccfc33123bbacb8c0aed2d1ad7f3ef2dc5f"
 dependencies = [
- "windows_aarch64_gnullvm 0.52.0",
- "windows_aarch64_msvc 0.52.0",
- "windows_i686_gnu 0.52.0",
- "windows_i686_msvc 0.52.0",
- "windows_x86_64_gnu 0.52.0",
- "windows_x86_64_gnullvm 0.52.0",
- "windows_x86_64_msvc 0.52.0",
+ "windows_aarch64_gnullvm 0.52.3",
+ "windows_aarch64_msvc 0.52.3",
+ "windows_i686_gnu 0.52.3",
+ "windows_i686_msvc 0.52.3",
+ "windows_x86_64_gnu 0.52.3",
+ "windows_x86_64_gnullvm 0.52.3",
+ "windows_x86_64_msvc 0.52.3",
 ]
 
 [[package]]
@@ -839,9 +901,9 @@ checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
 
 [[package]]
 name = "windows_aarch64_gnullvm"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb7764e35d4db8a7921e09562a0304bf2f93e0a51bfccee0bd0bb0b666b015ea"
+checksum = "68e5dcfb9413f53afd9c8f86e56a7b4d86d9a2fa26090ea2dc9e40fba56c6ec6"
 
 [[package]]
 name = "windows_aarch64_msvc"
@@ -851,9 +913,9 @@ checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbaa0368d4f1d2aaefc55b6fcfee13f41544ddf36801e793edbbfd7d7df075ef"
+checksum = "8dab469ebbc45798319e69eebf92308e541ce46760b49b18c6b3fe5e8965b30f"
 
 [[package]]
 name = "windows_i686_gnu"
@@ -863,9 +925,9 @@ checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a28637cb1fa3560a16915793afb20081aba2c92ee8af57b4d5f28e4b3e7df313"
+checksum = "2a4e9b6a7cac734a8b4138a4e1044eac3404d8326b6c0f939276560687a033fb"
 
 [[package]]
 name = "windows_i686_msvc"
@@ -875,9 +937,9 @@ checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ffe5e8e31046ce6230cc7215707b816e339ff4d4d67c65dffa206fd0f7aa7b9a"
+checksum = "28b0ec9c422ca95ff34a78755cfa6ad4a51371da2a5ace67500cf7ca5f232c58"
 
 [[package]]
 name = "windows_x86_64_gnu"
@@ -887,9 +949,9 @@ checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3d6fa32db2bc4a2f5abeacf2b69f7992cd09dca97498da74a151a3132c26befd"
+checksum = "704131571ba93e89d7cd43482277d6632589b18ecf4468f591fbae0a8b101614"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
@@ -899,9 +961,9 @@ checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1a657e1e9d3f514745a572a6846d3c7aa7dbe1658c056ed9c3344c4109a6949e"
+checksum = "42079295511643151e98d61c38c0acc444e52dd42ab456f7ccfd5152e8ecf21c"
 
 [[package]]
 name = "windows_x86_64_msvc"
@@ -911,6 +973,6 @@ checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.52.0"
+version = "0.52.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dff9641d1cd4be8d1a070daf9e3773c5f67e78b4d9d42263020c057706765c04"
+checksum = "0770833d60a970638e989b3fa9fd2bb1aaadcf88963d1659fd7d9990196ed2d6"
diff --git a/Cargo.toml b/Cargo.toml
index 1809e70..3f42c6b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,5 +3,6 @@ members = [
 	"talc-lang",
 	"talc-bin",
 	"talc-std",
+	"talc-macros",
 ]
 resolver = "2"
diff --git a/talc-bin/Cargo.toml b/talc-bin/Cargo.toml
index a85f938..38ae9c4 100644
--- a/talc-bin/Cargo.toml
+++ b/talc-bin/Cargo.toml
@@ -5,5 +5,7 @@ edition = "2021"
 
 [dependencies]
 talc-lang = { path = "../talc-lang" }
+talc-std = { path = "../talc-std" }
 rustyline = "13.0"
-clap = "4.5"
+clap = { version = "4.5", features = ["derive"] }
+ctrlc = "3.4"
diff --git a/talc-bin/src/main.rs b/talc-bin/src/main.rs
index 0d01072..04696e2 100644
--- a/talc-bin/src/main.rs
+++ b/talc-bin/src/main.rs
@@ -1,11 +1,60 @@
+use clap::Parser;
 use rustyline::error::ReadlineError;
-use talc_lang::{Parser, Vm, Symbol, value::{Value, Function}, compiler::repl};
-use std::{rc::Rc, io::Write};
+use talc_lang::{compiler::{compile, compile_repl}, value::{function::disasm_recursive, Value}, symbol::Symbol, Vm};
+use std::{rc::Rc, path::PathBuf, process::ExitCode};
 
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-	let parser = Parser::new();
+#[derive(Parser, Debug)]
+#[command(version, about, long_about = None)]
+struct Args {
+    file: Option<PathBuf>,
+
+    #[arg(short, long)]
+    repl: bool,
+
+    #[arg(short, long)]
+    disasm: bool,
+}
+
+fn exec(src: String, _args: &Args) -> ExitCode {
+	let parser = talc_lang::Parser::new();
 	let mut vm = Vm::new(256);
-	let mut globals = Vec::new();
+    talc_std::load_all(&mut vm);
+
+    let ex = match parser.parse(&src) {
+        Ok(ex) => ex,
+        Err(e) => { 
+            eprintln!("Error: {e}"); 
+            return ExitCode::FAILURE
+        },
+    };
+
+    let func = Rc::new(compile(&ex));
+
+    if let Err(e) = vm.call_no_args(func.clone()) {
+        eprintln!("{e}");
+        ExitCode::FAILURE
+    } else {
+        ExitCode::SUCCESS
+    }
+}
+
+fn repl(args: &Args) -> ExitCode {
+    if args.disasm {
+        eprintln!("input disassembly enabled");
+    }
+
+	let parser = talc_lang::Parser::new();
+	let mut compiler_globals = Vec::new();
+	let mut vm = Vm::new(256);
+    talc_std::load_all(&mut vm);
+
+    let interrupt = vm.get_interrupt();
+    let ctrlc_res = ctrlc::set_handler(move || {
+        interrupt.fetch_or(true, std::sync::atomic::Ordering::Relaxed);
+    });
+    if let Err(e) = ctrlc_res {
+        eprintln!("Warn: couldn't set ctrl+c handler: {e}")
+    }
 
 	let prev1_sym = Symbol::get("_");
 	let prev2_sym = Symbol::get("__");
@@ -15,13 +64,24 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 	vm.set_global(prev2_sym, Value::Nil);
 	vm.set_global(prev3_sym, Value::Nil);
 
-	let mut rl = rustyline::DefaultEditor::new()?;
+	let mut rl = match rustyline::DefaultEditor::new() {
+        Ok(rl) => rl,
+        Err(ReadlineError::Io(e)) => {
+            eprintln!("Error: {e}");
+            return ExitCode::FAILURE;
+        },
+        Err(ReadlineError::Errno(e)) => {
+            eprintln!("Error: {e}");
+            return ExitCode::FAILURE;
+        },
+        Err(_) => return ExitCode::SUCCESS,
+    };
 
 	loop {
 		let line = rl.readline(">> ");
 		let line = match line {
 			Ok(line) => line,
-			Err(ReadlineError::Eof) => break,
+			Err(ReadlineError::Eof) => return ExitCode::SUCCESS,
 			Err(ReadlineError::Interrupted) => continue,
 			Err(e) => {
 				eprintln!("Error: {e}");
@@ -34,14 +94,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 			Err(e) => { eprintln!("Error: {e}"); continue },
 		};
 
-		let (f, g) = repl(&ex, &globals);
-		globals = g;
+		let (f, g) = compile_repl(&ex, &compiler_globals);
+		compiler_globals = g;
 		let func = Rc::new(f);
+        
+        if args.disasm {
+            if let Err(e) = disasm_recursive(&func, &mut std::io::stderr()) {
+                eprintln!("Error: {e}");
+                return ExitCode::FAILURE
+            }
+        }
 
-		Function::disasm_recursive(func.clone(), &mut std::io::stdout())?;
-		std::io::stdout().flush()?;
-
-		match vm.run(func) {
+		match vm.call_no_args(func) {
 			Ok(v) => {
 				vm.set_global(prev3_sym, vm.get_global(prev2_sym).unwrap().clone());
 				vm.set_global(prev2_sym, vm.get_global(prev1_sym).unwrap().clone());
@@ -53,6 +117,20 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 			Err(e) => eprintln!("{e}"),
 		}
 	}
-
-	Ok(())
+}
+
+fn main() -> ExitCode {
+    let args = Args::parse();
+
+    if args.repl || args.file.is_none() {
+        return repl(&args)
+    }
+
+    match std::fs::read_to_string(args.file.as_ref().unwrap()) {
+        Ok(s) => exec(s, &args),
+        Err(e) => {
+            eprintln!("Error: {e}");
+            ExitCode::FAILURE
+        }
+    }
 }
diff --git a/talc-lang/Cargo.toml b/talc-lang/Cargo.toml
index 07144db..aa4ea01 100644
--- a/talc-lang/Cargo.toml
+++ b/talc-lang/Cargo.toml
@@ -8,6 +8,7 @@ lalrpop-util = { version = "0.20", features = ["lexer", "unicode"] }
 num-complex = "0.4"
 num-rational = { version = "0.4", default-features = false, features = [] }
 thiserror = "1.0"
+lazy_static = "1.4"
 
 [build-dependencies]
 lalrpop = { version = "0.20", default_features = false, features = ["lexer", "unicode"]}
diff --git a/talc-lang/src/ast.rs b/talc-lang/src/ast.rs
index 3fcc2a8..c2b6297 100644
--- a/talc-lang/src/ast.rs
+++ b/talc-lang/src/ast.rs
@@ -1,4 +1,4 @@
-use crate::{value::Value, Symbol};
+use crate::{value::Value, symbol::Symbol};
 
 #[derive(Clone, Copy, Debug)]
 pub enum BinaryOp {
@@ -33,6 +33,7 @@ pub enum Expr<'s> {
 	List(Vec<Expr<'s>>),
 	Table(Vec<(Expr<'s>, Expr<'s>)>),
 
+    Return(Box<Expr<'s>>),
 	And(Box<Expr<'s>>, Box<Expr<'s>>),
 	Or(Box<Expr<'s>>, Box<Expr<'s>>),
 	If(Box<Expr<'s>>, Box<Expr<'s>>, Option<Box<Expr<'s>>>),
diff --git a/talc-lang/src/chunk.rs b/talc-lang/src/chunk.rs
index d16581f..2c9f1bf 100644
--- a/talc-lang/src/chunk.rs
+++ b/talc-lang/src/chunk.rs
@@ -117,7 +117,7 @@ pub enum Instruction {
 	JumpTrue(Arg24),
 	JumpFalse(Arg24),
 
-	IterBegin, IterTest(Arg24),
+	IterBegin, IterNext(Arg24),
 
 	BeginTry(Arg24), EndTry,
 
@@ -159,7 +159,7 @@ impl std::fmt::Display for Instruction {
 			Self::JumpTrue(a) => write!(f, "jumptrue {}", usize::from(a)),
 			Self::JumpFalse(a) => write!(f, "jumpfalse {}", usize::from(a)),
 			Self::IterBegin => write!(f, "iterbegin"),
-			Self::IterTest(a) => write!(f, "itertest {}", usize::from(a)),
+			Self::IterNext(a) => write!(f, "iternext {}", usize::from(a)),
 			Self::BeginTry(t) => write!(f, "begintry {}", usize::from(t)),
 			Self::EndTry => write!(f, "endtry"),
 			Self::Call(n) => write!(f, "call {n}"),
diff --git a/talc-lang/src/compiler.rs b/talc-lang/src/compiler.rs
index e127812..d55ddb0 100644
--- a/talc-lang/src/compiler.rs
+++ b/talc-lang/src/compiler.rs
@@ -3,7 +3,7 @@ use std::rc::Rc;
 use crate::ast::{BinaryOp, Expr, LValue, CatchBlock};
 use crate::chunk::{Instruction as I, Chunk, Arg24, Catch};
 use crate::symbol::Symbol;
-use crate::value::Function;
+use crate::value::function::Function;
 use crate::value::Value;
 
 #[derive(Debug, Clone)]
@@ -14,51 +14,75 @@ pub struct Local {
 
 #[derive(Clone, Copy, PartialEq, Eq)]
 enum CompilerMode {
-	Function, Repl, // Module,
+	Function, Repl, Module,
 }
 
 struct Compiler<'a> {
-	parent: Option<&'a Compiler<'a>>,
 	mode: CompilerMode,
+	parent: Option<&'a Compiler<'a>>,
 	func: Function,
 	scope: usize,
 	locals: Vec<Local>,
 	globals: Vec<Local>,
 }
 
-pub fn repl(expr: &Expr, globals: &[Local]) -> (Function, Vec<Local>)  {
-	let locals = vec![Local {
-		name: "self".into(),
-		scope: 0,
-	}];
-	let mut comp = Compiler {
-		parent: None,
-		mode: CompilerMode::Repl,
-		func: Function { arity: 0, chunk: Chunk::new() },
-		scope: 0,
-		locals,
-		globals: globals.to_vec(),
-	};
+pub fn compile(expr: &Expr) -> Function  {
+    let mut comp = Compiler::new_module(None);
 	comp.expr(expr);
-	comp.emit(I::Return);
-	(comp.func, comp.globals)
+    comp.finish()
+}
+
+pub fn compile_repl(expr: &Expr, globals: &[Local]) -> (Function, Vec<Local>)  {
+    let mut comp = Compiler::new_repl(globals);
+	comp.expr(expr);
+    comp.finish_repl()
+}
+
+impl<'a> Default for Compiler<'a> {
+    fn default() -> Self {
+        let locals = vec![Local {
+            name: "self".into(),
+            scope: 0,
+        }];
+        Self {
+            mode: CompilerMode::Function,
+            parent: None,
+            func: Function { arity: 0, chunk: Chunk::new() },
+            scope: 0,
+            locals,
+            globals: Vec::new(),
+        }
+    }
 }
 
 impl<'a> Compiler<'a> {
-	fn new_function(&'a self, func: Function, args: &[&str]) -> Self {
-		let mut new = Self {
-			parent: Some(self),
-			mode: CompilerMode::Function,
-			func,
-			scope: 0,
-			locals: Vec::new(),
-			globals: Vec::new(),
-		};
+	fn new_repl(globals: &[Local]) -> Self {
+        Self {
+            mode: CompilerMode::Repl,
+            globals: globals.to_vec(),
+            ..Self::default()
+        }
+    }
 
-		new.locals.push(Local {
-			name: "self".into(),
-			scope: 0,
-		});
+	fn new_module(parent: Option<&'a Self>) -> Self {
+        Self {
+            mode: CompilerMode::Module,
+            parent,
+            ..Self::default()
+        }
+    }
+
+	fn new_function(&'a self, args: &[&str]) -> Self {
+        let func = Function {
+            arity: args.len(),
+            chunk: Chunk::new(),
+        };
+        let mut new = Self {
+			mode: CompilerMode::Function,
+			parent: Some(self),
+            func,
+            ..Self::default()
+        };
 
 		for arg in args {
 			new.locals.push(Local {
@@ -75,6 +99,11 @@ impl<'a> Compiler<'a> {
 		self.func
 	}
 
+	pub fn finish_repl(mut self) -> (Function, Vec<Local>) {
+		self.emit(I::Return);
+		(self.func, self.globals)
+	}
+
 	//
 	//  Utility
 	//
@@ -339,6 +368,10 @@ impl<'a> Compiler<'a> {
 				}
 				self.emit(I::Call(args.len() as u8));
 			},
+            Expr::Return(e) => {
+                self.expr(e);
+                self.emit(I::Return);
+            },
 			Expr::Pipe(a, f) => {
 				self.expr(a);
 				self.expr(f);
@@ -447,9 +480,7 @@ impl<'a> Compiler<'a> {
 		let start = self.ip();
 
 		// call iterator and jump if nil, otherwise store
-		self.emit(I::Dup);
-		self.emit(I::Call(0));
-		let j1 = self.emit(I::IterTest(Arg24::from_usize(0)));
+		let j1 = self.emit(I::IterNext(Arg24::from_usize(0)));
 		self.store_local(local);
 
 		// body
@@ -459,21 +490,17 @@ impl<'a> Compiler<'a> {
 		// end loop
 		self.emit(I::Jump(Arg24::from_usize(start)));
 
-		self.update_instr(j1, I::IterTest(Arg24::from_usize(self.ip())));
+		self.update_instr(j1, I::IterNext(Arg24::from_usize(self.ip())));
 		self.end_scope();
 		self.emit(I::Nil);
 	}
 
 	fn expr_lambda(&mut self, args: &[&str], body: &Expr) {
-		let func = Function {
-			arity: args.len(),
-			chunk: Chunk::new()
-		};
-		let mut inner = self.new_function(func, args);
+		let mut inner = self.new_function(args);
 		inner.parent = Some(self);
 		inner.expr(body);
 		let func = inner.finish();
-		let n = self.add_const(Value::Function(Rc::new(func)));
+		let n = self.add_const(func.into());
 		self.emit(I::Const(Arg24::from_usize(n)));
 	}
 
diff --git a/talc-lang/src/lib.rs b/talc-lang/src/lib.rs
index 54d9efc..8fda026 100644
--- a/talc-lang/src/lib.rs
+++ b/talc-lang/src/lib.rs
@@ -11,7 +11,7 @@ mod parser {
 }
 mod parser_util;
 mod vm;
-mod symbol;
+pub mod symbol;
 
 pub mod ast;
 pub mod value;
@@ -21,8 +21,6 @@ pub mod compiler;
 
 pub use parser::BlockParser as Parser;
 pub use vm::Vm;
-pub use symbol::Symbol;
-
 
 type LexResult<'input> = Result<
 	(usize, Token<'input>, usize),
diff --git a/talc-lang/src/parser.lalrpop b/talc-lang/src/parser.lalrpop
index 4c50924..98bdfa0 100644
--- a/talc-lang/src/parser.lalrpop
+++ b/talc-lang/src/parser.lalrpop
@@ -48,6 +48,7 @@ match {
 	"break",
 	"try",
 	"catch",
+	"return",
 } else {
 	// identifiers
 	r"[a-zA-Z_][a-zA-Z0-9_]*" => TokIdentifier,
@@ -81,7 +82,10 @@ pub Block: Box<Expr<'input>> = {
 }
 
 
-Expr: Box<Expr<'input>> = Assign;
+Expr: Box<Expr<'input>> = {
+	"return" <e:Expr> => Box::new(Expr::Return(e)),
+	Assign,
+}
 
 //
 //  assignment
diff --git a/talc-lang/src/symbol.rs b/talc-lang/src/symbol.rs
index ab1d377..c3a3d72 100644
--- a/talc-lang/src/symbol.rs
+++ b/talc-lang/src/symbol.rs
@@ -1,4 +1,6 @@
-use std::{sync::{OnceLock, Arc, Mutex}, collections::HashMap};
+use std::{collections::HashMap, sync::{Arc, Mutex, OnceLock}};
+
+use lazy_static::lazy_static;
 
 #[derive(Default)]
 struct SymbolTable {
@@ -6,7 +8,21 @@ struct SymbolTable {
 	values: HashMap<Arc<str>, Symbol>
 }
 
-static SYM_TABLE: OnceLock<Mutex<SymbolTable>> = OnceLock::new();
+lazy_static! {
+    pub static ref SYM_TYPE: Symbol = symbol!(type);
+    pub static ref SYM_MSG: Symbol = symbol!(msg);
+    pub static ref SYM_DATA: Symbol = symbol!(data);
+
+    pub static ref SYM_TYPE_ERROR: Symbol = symbol!(type_error);
+    pub static ref SYM_NAME_ERROR: Symbol = symbol!(name_error);
+    pub static ref SYM_INDEX_ERROR: Symbol = symbol!(index_error);
+    pub static ref SYM_HASH_ERROR: Symbol = symbol!(hash_error);
+    pub static ref SYM_CALL_STACK_OVERFLOW: Symbol = symbol!(call_stack_overflow);
+    pub static ref SYM_INTERRUPTED: Symbol = symbol!(interrupted);
+    pub static ref SYM_STOP_ITERATOR: Symbol = symbol!(stop_iterator);
+}
+
+static TABLE: OnceLock<Mutex<SymbolTable>> = OnceLock::new();
 
 const MAX_SYMBOL: usize = 0xff_ffff;
 
@@ -14,7 +30,7 @@ const MAX_SYMBOL: usize = 0xff_ffff;
 pub struct Symbol(u32);
 
 fn get_table() -> &'static Mutex<SymbolTable> {
-	SYM_TABLE.get_or_init(|| Mutex::new(SymbolTable::default()))
+	TABLE.get_or_init(|| Mutex::new(SymbolTable::default()))
 }
 
 impl Symbol {
@@ -74,3 +90,15 @@ impl Symbol {
 		table.names.get(self.0 as usize).cloned().expect("symbol does not exist")
 	}
 }
+
+#[macro_export]
+macro_rules! symbol {
+    ($sym:ident) => {
+        $crate::symbol::Symbol::get(stringify!($sym))
+    };
+    ($sym:literal) => {
+        $crate::symbol::Symbol::get($sym)
+    };
+}
+
+pub use symbol;
diff --git a/talc-lang/src/value/exception.rs b/talc-lang/src/value/exception.rs
new file mode 100644
index 0000000..6e0b5e9
--- /dev/null
+++ b/talc-lang/src/value/exception.rs
@@ -0,0 +1,98 @@
+use std::{rc::Rc, collections::HashMap, cell::RefCell, fmt::Display};
+use super::{HashValue, RcTable, Value};
+use crate::{symbol::{SYM_DATA, SYM_MSG, SYM_TYPE}, symbol::Symbol};
+
+pub type Result<T> = std::result::Result<T, Exception>;
+
+#[derive(Clone, Debug)]
+pub struct Exception {
+	pub ty: Symbol,
+	pub msg: Option<Rc<str>>,
+	pub data: Option<Value>,
+}
+
+impl Exception {
+	pub fn new(ty: Symbol) -> Self {
+		Self { ty, msg: None, data: None }
+	}
+
+	pub fn new_with_msg(ty: Symbol, msg: Rc<str>) -> Self {
+		Self { ty, msg: Some(msg), data: None }
+	}
+
+	pub fn from_table(table: &Rc<RefCell<HashMap<HashValue, Value>>>) -> Option<Self> {
+        let table = table.borrow();
+		let ty = table.get(&(*SYM_TYPE).into())?;
+		if let Value::Symbol(ty) = ty {
+			let data = table.get(&(*SYM_DATA).into()).cloned();
+            let msg = table.get(&(*SYM_MSG).into());
+            match msg {
+                None => Some(Self {
+                    ty: *ty,
+                    data,
+                    msg: None,
+                }),
+                Some(Value::String(msg)) => Some(Self {
+                    ty: *ty,
+                    data,
+                    msg: Some(msg.clone()),
+                }),
+                Some(_) => None,
+            }
+		} else {
+			None
+		}
+	}
+
+	pub fn to_table(self) -> RcTable {
+		let mut table = HashMap::new();
+		table.insert((*SYM_TYPE).into(), self.ty.into());
+		if let Some(msg) = self.msg {
+			table.insert((*SYM_MSG).into(), Value::String(msg));
+		}
+		if let Some(data) = self.data {
+			table.insert((*SYM_DATA).into(), data);
+		}
+		Rc::new(RefCell::new(table))
+	}
+}
+
+impl Display for Exception {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Some(msg) = &self.msg {
+            write!(f, "{}: {}", self.ty.name(), msg)
+        } else {
+            write!(f, "{}", self.ty.name())
+        }
+	}
+}
+
+#[macro_export]
+macro_rules! exception {
+	($exc_ty:expr, $fstr:literal, $($arg:expr),*) => {
+		$crate::value::exception::Exception::new_with_msg(
+			$exc_ty,
+			format!($fstr, $($arg),*).into()
+		)
+	};
+	($exc_ty:expr, $fstr:literal) => {
+		$crate::value::exception::exception!($exc_ty, $fstr,)
+	};
+	($exc_ty:expr) => {
+		$crate::value::exception::Exception::new($exc_ty)
+	};
+}
+
+pub use exception;
+
+#[macro_export]
+macro_rules! throw {
+	($($args:tt)*) => {
+        return Err($crate::value::exception::exception!($($args)*))
+	};
+}
+
+pub use throw;
+
+
+
diff --git a/talc-lang/src/value/function.rs b/talc-lang/src/value/function.rs
new file mode 100644
index 0000000..36ff31f
--- /dev/null
+++ b/talc-lang/src/value/function.rs
@@ -0,0 +1,72 @@
+use std::rc::Rc;
+
+use crate::{chunk::Chunk, Vm};
+
+use super::{Value, exception::Result};
+
+#[derive(Debug, Default)]
+pub struct Function {
+	pub arity: usize,
+	pub chunk: Chunk,
+}
+
+pub struct NativeFunc {
+	pub arity: usize,
+    #[allow(clippy::type_complexity)]
+	pub f: Box<dyn Fn(&mut Vm, Vec<Value>) -> Result<Value>>,
+}
+
+impl std::fmt::Debug for NativeFunc {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+		f.debug_struct("NativeFunc")
+			.field("arity", &self.arity)
+			.finish_non_exhaustive()
+	}
+}
+
+pub fn disasm_recursive(f: &Rc<Function>, w: &mut impl std::io::Write) -> std::io::Result<()> {
+    writeln!(w, "{} (argc={})", Value::Function(f.clone()), f.arity)?;
+    if !f.chunk.consts.is_empty() {
+        writeln!(w, "constants")?;
+        for (i, c) in f.chunk.consts.iter().enumerate() {
+            writeln!(w, "  {i:04}: {c}")?;
+        }
+    }
+    if !f.chunk.try_tables.is_empty() {
+        writeln!(w, "catch tables")?;
+        for (i, n) in f.chunk.try_tables.iter().enumerate() {
+            write!(w, "  {i:04}: ")?;
+            if n.catches.is_empty() {
+                writeln!(w)?;
+            }
+            for (i, catch) in n.catches.iter().enumerate() {
+                if i != 0 {
+                    write!(w, "      : ")?;
+                }
+                if let Some(types) = &catch.types {
+                    write!(w, "{:04} [", catch.addr)?;
+                    for (i, ty) in types.iter().enumerate() {
+                        if i != 0 { write!(w, ", ")?; }
+                        write!(w, "{}", ty.name())?;
+                    }
+                    writeln!(w, "]")?;
+                } else {
+                    writeln!(w, "{:04} *", catch.addr)?;
+                }
+            }
+        }
+    }
+    writeln!(w, "instructions")?;
+    for (i, n) in f.chunk.instrs.iter().enumerate() {
+        writeln!(w, "  {i:04}: {n}")?;
+    }
+    writeln!(w)?;
+
+    for c in &f.chunk.consts {
+        if let Value::Function(f) = c {
+            disasm_recursive(f, w)?;
+        }
+    }
+    Ok(())
+}
+
diff --git a/talc-lang/src/value/mod.rs b/talc-lang/src/value/mod.rs
new file mode 100644
index 0000000..7a9791e
--- /dev/null
+++ b/talc-lang/src/value/mod.rs
@@ -0,0 +1,190 @@
+use std::{rc::Rc, cell::RefCell, collections::HashMap, hash::Hash, fmt::Display};
+
+use num_complex::Complex64;
+use num_rational::Rational64;
+
+use crate::symbol::{SYM_HASH_ERROR, Symbol};
+
+use self::{range::{Range, RangeType}, function::{Function, NativeFunc}, exception::{Exception, throw}};
+
+pub mod exception;
+pub mod function;
+pub mod ops;
+pub mod range;
+
+type RcList = Rc<RefCell<Vec<Value>>>;
+type RcTable = Rc<RefCell<HashMap<HashValue, Value>>>;
+
+#[derive(Clone, Debug)]
+pub enum Value {
+	Nil,
+	Bool(bool),
+	Symbol(Symbol),
+	Range(Range),
+
+	Int(i64),
+	Float(f64),
+	Ratio(Rational64),
+	Complex(Complex64),
+
+	String(Rc<str>),
+	List(RcList),
+	Table(RcTable),
+	Function(Rc<Function>),
+	NativeFunc(Rc<NativeFunc>),
+}
+
+impl Display for Value {
+	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+		match self {
+			Value::Nil => write!(f, "nil"),
+			Value::Bool(b) => write!(f, "{b}"),
+			Value::Symbol(s) => write!(f, ":{}", s.name()),
+			Value::Range(r) => match r.ty {
+				RangeType::Open => write!(f, "{}..{}", r.start, r.stop),
+				RangeType::Closed => write!(f, "{}..={}", r.start, r.stop),
+				RangeType::Endless => write!(f, "{}..*", r.start),
+			},
+			Value::Int(n) => write!(f, "{n}"),
+			Value::Float(x) => write!(f, "{x:?}"),
+			Value::Ratio(r) => write!(f, "{}/{}", r.numer(), r.denom()),
+			Value::Complex(z) => write!(f, "{z}"),
+
+			Value::String(s) => {
+				if f.alternate() {
+					write!(f, "{s:?}")
+				} else {
+					write!(f, "{s}")
+				}
+			},
+			Value::List(l) => {
+				write!(f, "[")?;
+				for (i, item) in l.borrow().iter().enumerate() {
+					if i != 0 {
+						write!(f, ", ")?;
+					}
+					if f.alternate() {
+						write!(f, "{item:#}")?;
+					} else {
+						write!(f, "{item}")?;
+					}
+				}
+				write!(f, "]")
+			},
+			Value::Table(t) => {
+				write!(f, "{{ ")?;
+				for (i, (k, v)) in t.borrow().iter().enumerate() {
+					if i != 0 {
+						write!(f, ", ")?;
+					}
+					if f.alternate() {
+						write!(f, "({:#}) = {v:#}", k.0)?;
+					} else {
+						write!(f, "({}) = {v}", k.0)?;
+					}
+				}
+				write!(f, " }}")
+			},
+			Value::Function(g)
+				=> write!(f, "<function {:?}>", Rc::as_ptr(g)),
+			Value::NativeFunc(g)
+				=> write!(f, "<native function {:?}>", Rc::as_ptr(g)),
+		}
+	}
+}
+
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct HashValue(Value);
+
+impl Eq for HashValue {}
+
+impl TryFrom<Value> for HashValue {
+	type Error = Exception;
+	fn try_from(value: Value) -> std::result::Result<Self, Self::Error> {
+		match value {
+			Value::Nil
+			| Value::Bool(_)
+			| Value::Symbol(_)
+			| Value::Int(_)
+			| Value::Ratio(_)
+			| Value::String(_) => Ok(Self(value)),
+			_ => throw!(*SYM_HASH_ERROR, "value {value:#} cannot be hashed"),
+		}
+	}
+}
+
+impl HashValue {
+	pub fn into_inner(self) -> Value { self.0 }
+}
+
+impl Hash for HashValue {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		std::mem::discriminant(&self.0).hash(state);
+		match &self.0 {
+			Value::Nil => (),
+			Value::Bool(b) => b.hash(state),
+			Value::Symbol(s) => s.hash(state),
+			Value::Int(n) => n.hash(state),
+			Value::Ratio(r) => r.hash(state),
+			Value::String(s) => s.hash(state),
+			_ => unreachable!(),
+		}
+	}
+}
+
+macro_rules! impl_from {
+    ($ty:ty, $var:ident) => {
+        impl From<$ty> for Value {
+            fn from(value: $ty) -> Self { Self::$var(value) }
+        }
+    };
+    ($ty:ty, $var:ident, hash) => {
+        impl From<$ty> for Value {
+            fn from(value: $ty) -> Self { Self::$var(value) }
+        }
+        impl From<$ty> for HashValue {
+            fn from(value: $ty) -> Self { Self(Value::$var(value)) }
+        }
+    };
+    ($ty:ty, $var:ident, rc) => {
+        impl From<$ty> for Value {
+            fn from(value: $ty) -> Self { Self::$var(Rc::new(value)) }
+        }
+        impl From<Rc<$ty>> for Value {
+            fn from(value: Rc<$ty>) -> Self { Self::$var(value) }
+        }
+    };
+    ($ty:ty, $var:ident, rcref) => {
+        impl From<$ty> for Value {
+            fn from(value: $ty) -> Self { Self::$var(Rc::new(RefCell::new(value))) }
+        }
+        impl From<RefCell<$ty>> for Value {
+            fn from(value: RefCell<$ty>) -> Self { Self::$var(Rc::new(value)) }
+        }
+        impl From<Rc<RefCell<$ty>>> for Value {
+            fn from(value: Rc<RefCell<$ty>>) -> Self { Self::$var(value) }
+        }
+    };
+    ($ty:ty, $var:ident, into) => {
+        impl From<$ty> for Value {
+            fn from(value: $ty) -> Self { Self::$var(value.into()) }
+        }
+    };
+}
+
+impl_from!(bool, Bool, hash);
+impl_from!(Symbol, Symbol, hash);
+impl_from!(Range, Range);
+impl_from!(i64, Int, hash);
+impl_from!(f64, Float);
+impl_from!(Rational64, Ratio, hash);
+impl_from!(Complex64, Complex);
+impl_from!(HashMap<HashValue, Value>, Table, rcref);
+impl_from!(Vec<Value>, List, rcref);
+impl_from!(Function, Function, rc);
+impl_from!(NativeFunc, NativeFunc, rc);
+impl_from!(Rc<str>, String);
+impl_from!(&str, String, into);
+impl_from!(Box<str>, String, into);
+impl_from!(String, String, into);
diff --git a/talc-lang/src/value.rs b/talc-lang/src/value/ops.rs
similarity index 53%
rename from talc-lang/src/value.rs
rename to talc-lang/src/value/ops.rs
index 1feb263..8d96ea9 100644
--- a/talc-lang/src/value.rs
+++ b/talc-lang/src/value/ops.rs
@@ -1,321 +1,11 @@
-use std::cell::RefCell;
-use std::collections::HashMap;
-use std::fmt::Display;
-use std::ops::{Add, Sub, Mul, Div, Neg};
-use std::cmp::Ordering;
-use std::rc::Rc;
-use std::hash::Hash;
-use num_rational::Rational64;
+use std::{ops::{Neg, Add, Sub, Mul, Div}, cmp::Ordering, cell::RefCell};
+
 use num_complex::Complex64;
+use num_rational::Rational64;
 
-use crate::chunk::Chunk;
-use crate::symbol::Symbol;
+use crate::{symbol::{SYM_INDEX_ERROR, SYM_STOP_ITERATOR, SYM_TYPE_ERROR}, value::range::RangeType, Vm};
 
-type RcList = Rc<RefCell<Vec<Value>>>;
-type RcTable = Rc<RefCell<HashMap<HashValue, Value>>>;
-
-#[derive(Clone, Debug)]
-pub struct Exception {
-	pub ty: Symbol,
-	pub msg: Rc<str>,
-	pub data: Option<Value>,
-}
-
-impl Exception {
-	pub fn new(ty: Symbol, msg: Rc<str>) -> Self {
-		Self { ty, msg, data: None }
-	}
-
-	pub fn from_table(table: RcTable) -> Option<Self> {
-		let table = table.borrow();
-		let ty = table.get(&Symbol::get("type").into())?;
-		let msg = table.get(&Symbol::get("msg").into())?;
-		if let (Value::Symbol(ty), Value::String(msg)) = (ty, msg) {
-			let data = table.get(&Symbol::get("data").into());
-			Some(Self {
-				ty: *ty,
-				msg: msg.clone(),
-				data: data.cloned(),
-			})
-		} else {
-			None
-		}
-	}
-
-	pub fn to_table(self) -> RcTable {
-		let mut table = HashMap::new();
-		table.insert(Symbol::get("type").into(), self.ty.into());
-		table.insert(Symbol::get("msg").into(), Value::String(self.msg));
-		if let Some(data) = self.data {
-			table.insert(Symbol::get("data").into(), data);
-		}
-		Rc::new(RefCell::new(table))
-	}
-}
-
-impl Display for Exception {
-	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-		write!(f, "{}: {}", self.ty.name(), self.msg)
-	}
-}
-
-pub type Result<T> = std::result::Result<T, Exception>;
-
-macro_rules! exception {
-	($exc_ty:ident, $fstr:literal, $($arg:expr),*) => {{
-		$crate::value::Exception::new(
-			$crate::Symbol::get(stringify!($exc_ty)),
-			format!($fstr, $($arg),*).into()
-		)
-	}};
-	($exc_ty:ident, $fstr:literal) => {{
-		$crate::value::exception!($exc_ty, $fstr,)
-	}};
-}
-
-pub(crate) use exception;
-
-macro_rules! throw {
-	($($args:tt)*) => {
-		return Err($crate::value::exception!($($args)*))
-	};
-}
-
-pub(crate) use throw;
-
-
-#[derive(Debug, Default)]
-pub struct Function {
-	pub arity: usize,
-	pub chunk: Chunk,
-}
-
-impl Function {
-	pub fn disasm_recursive(f: Rc<Function>, w: &mut impl std::io::Write) -> std::io::Result<()> {
-		writeln!(w, "{} (argc={})", Value::Function(f.clone()), f.arity)?;
-		if !f.chunk.consts.is_empty() {
-			writeln!(w, "constants")?;
-			for (i, c) in f.chunk.consts.iter().enumerate() {
-				writeln!(w, "  {i:04}: {c}")?;
-			}
-		}
-		if !f.chunk.try_tables.is_empty() {
-			writeln!(w, "catch tables")?;
-			for (i, n) in f.chunk.try_tables.iter().enumerate() {
-				write!(w, "  {i:04}: ")?;
-				if n.catches.is_empty() {
-					writeln!(w)?;
-				}
-				for (i, catch) in n.catches.iter().enumerate() {
-					if i != 0 {
-						write!(w, "      : ")?;
-					}
-					if let Some(types) = &catch.types {
-						write!(w, "{:04} [", catch.addr)?;
-						for (i, ty) in types.iter().enumerate() {
-							if i != 0 { write!(w, ", ")?; }
-							write!(w, "{}", ty.name())?;
-						}
-						writeln!(w, "]")?;
-					} else {
-						writeln!(w, "{:04} *", catch.addr)?;
-					}
-				}
-			}
-		}
-		writeln!(w, "instructions")?;
-		for (i, n) in f.chunk.instrs.iter().enumerate() {
-			writeln!(w, "  {i:04}: {n}")?;
-		}
-		writeln!(w)?;
-
-		for c in &f.chunk.consts {
-			if let Value::Function(f) = c {
-				Function::disasm_recursive(f.clone(), w)?;
-			}
-		}
-		Ok(())
-	}
-}
-
-pub struct NativeFunc {
-	pub arity: usize,
-	pub f: Box<dyn Fn(Value, Vec<Value>) -> Result<Value>>,
-}
-
-impl std::fmt::Debug for NativeFunc {
-	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-		f.debug_struct("NativeFunc")
-			.field("arity", &self.arity)
-			.finish_non_exhaustive()
-	}
-}
-
-#[derive(Clone, Debug, PartialEq)]
-pub struct HashValue(Value);
-
-impl Eq for HashValue {}
-
-impl TryFrom<Value> for HashValue {
-	type Error = Exception;
-	fn try_from(value: Value) -> std::result::Result<Self, Self::Error> {
-		match value {
-			Value::Nil
-			| Value::Bool(_)
-			| Value::Symbol(_)
-			| Value::Int(_)
-			| Value::Ratio(_)
-			| Value::String(_) => Ok(Self(value)),
-			_ => throw!(hash, "value {value:#} cannot be hashed"),
-		}
-	}
-}
-
-impl HashValue {
-	pub fn into_inner(self) -> Value { self.0 }
-}
-
-impl Hash for HashValue {
-	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-		std::mem::discriminant(&self.0).hash(state);
-		match &self.0 {
-			Value::Nil => (),
-			Value::Bool(b) => b.hash(state),
-			Value::Symbol(s) => s.hash(state),
-			Value::Int(n) => n.hash(state),
-			Value::Ratio(r) => r.hash(state),
-			Value::String(s) => s.hash(state),
-			_ => unreachable!(),
-		}
-	}
-}
-
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum RangeType {
-	Open, Closed, Endless,
-}
-
-#[derive(Clone, Copy, Debug)]
-pub struct Range {
-	start: i64,
-	stop: i64,
-	ty: RangeType,
-}
-
-impl Range {
-	pub fn len(&self) -> Option<usize> {
-		match self.ty {
-			RangeType::Open => Some((self.stop - self.start).max(0) as usize),
-			RangeType::Closed => Some((self.stop - self.start + 1).max(0) as usize),
-			RangeType::Endless => None,
-		}
-	}
-
-	pub fn is_empty(&self) -> bool {
-		match self.ty {
-			RangeType::Open => self.stop - self.start <= 0,
-			RangeType::Closed => self.stop - self.start < 0,
-			RangeType::Endless => false,
-		}
-	}
-}
-
-impl IntoIterator for Range {
-	type Item = i64;
-	type IntoIter = Box<dyn Iterator<Item=i64>>;
-	fn into_iter(self) -> Self::IntoIter {
-		match self.ty {
-			RangeType::Open => Box::new(self.start..self.stop),
-			RangeType::Closed => Box::new(self.start..=self.stop),
-			RangeType::Endless => Box::new(self.start..),
-		}
-	}
-}
-
-#[derive(Clone, Debug)]
-pub enum Value {
-	Nil,
-	Bool(bool),
-	Symbol(Symbol),
-	Range(Range),
-
-	Int(i64),
-	Float(f64),
-	Ratio(Rational64),
-	Complex(Complex64),
-
-	String(Rc<str>),
-	List(RcList),
-	Table(RcTable),
-	Function(Rc<Function>),
-	NativeFunc(Rc<NativeFunc>),
-}
-
-impl From<Symbol> for Value {
-	fn from(value: Symbol) -> Self { Self::Symbol(value) }
-}
-impl From<Symbol> for HashValue {
-	fn from(value: Symbol) -> Self { Self(value.into()) }
-}
-
-impl Display for Value {
-	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-		match self {
-			Value::Nil => write!(f, "nil"),
-			Value::Bool(b) => write!(f, "{b}"),
-			Value::Symbol(s) => write!(f, ":{}", s.name()),
-			Value::Range(r) => match r.ty {
-				RangeType::Open => write!(f, "{}..{}", r.start, r.stop),
-				RangeType::Closed => write!(f, "{}..={}", r.start, r.stop),
-				RangeType::Endless => write!(f, "{}..*", r.start),
-			},
-			Value::Int(n) => write!(f, "{n}"),
-			Value::Float(x) => write!(f, "{x:?}"),
-			Value::Ratio(r) => write!(f, "{}/{}", r.numer(), r.denom()),
-			Value::Complex(z) => write!(f, "{z}"),
-
-			Value::String(s) => {
-				if f.alternate() {
-					write!(f, "{s:?}")
-				} else {
-					write!(f, "{s}")
-				}
-			},
-			Value::List(l) => {
-				write!(f, "[")?;
-				for (i, item) in l.borrow().iter().enumerate() {
-					if i != 0 {
-						write!(f, ", ")?;
-					}
-					if f.alternate() {
-						write!(f, "{item:#}")?;
-					} else {
-						write!(f, "{item}")?;
-					}
-				}
-				write!(f, "]")
-			},
-			Value::Table(t) => {
-				write!(f, "{{ ")?;
-				for (i, (k, v)) in t.borrow().iter().enumerate() {
-					if i != 0 {
-						write!(f, ", ")?;
-					}
-					if f.alternate() {
-						write!(f, "({:#}) = {v:#}", k.0)?;
-					} else {
-						write!(f, "({}) = {v}", k.0)?;
-					}
-				}
-				write!(f, " }}")
-			},
-			Value::Function(g)
-				=> write!(f, "<function {:?}>", Rc::as_ptr(g)),
-			Value::NativeFunc(g)
-				=> write!(f, "<native function {:?}>", Rc::as_ptr(g)),
-		}
-	}
-}
+use super::{Value, exception::{Result, throw}, range::Range, function::NativeFunc, HashValue};
 
 impl Value {
 	pub fn truthy(&self) -> bool {
@@ -371,7 +61,7 @@ impl Neg for Value {
 			V::Ratio(x) => Ok(V::Ratio(-x)),
 			V::Float(x) => Ok(V::Float(-x)),
 			V::Complex(x) => Ok(V::Complex(-x)),
-			a => throw!(type_error, "cannot negate {a:#}")
+			a => throw!(*SYM_TYPE_ERROR, "cannot negate {a:#}")
 		}
 	}
 }
@@ -385,7 +75,7 @@ impl Add<Value> for Value {
 			(V::Ratio(x), V::Ratio(y)) => Ok(V::Ratio(x + y)),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x + y)),
 			(V::Complex(x), V::Complex(y)) => Ok(V::Complex(x + y)),
-			(l, r) => throw!(type_error, "cannot add {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot add {l:#} and {r:#}")
 		}
 	}
 }
@@ -399,7 +89,7 @@ impl Sub<Value> for Value {
 			(V::Ratio(x), V::Ratio(y)) => Ok(V::Ratio(x - y)),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x - y)),
 			(V::Complex(x), V::Complex(y)) => Ok(V::Complex(x - y)),
-			(l, r) => throw!(type_error, "cannot subtract {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot subtract {l:#} and {r:#}")
 		}
 	}
 }
@@ -413,7 +103,7 @@ impl Mul<Value> for Value {
 			(V::Ratio(x), V::Ratio(y)) => Ok(V::Ratio(x * y)),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x * y)),
 			(V::Complex(x), V::Complex(y)) => Ok(V::Complex(x * y)),
-			(l, r) => throw!(type_error, "cannot multiply {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot multiply {l:#} and {r:#}")
 		}
 	}
 }
@@ -427,7 +117,7 @@ impl Div<Value> for Value {
 			(V::Ratio(x), V::Ratio(y)) => Ok(V::Ratio(x / y)),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x / y)),
 			(V::Complex(x), V::Complex(y)) => Ok(V::Complex(x / y)),
-			(l, r) => throw!(type_error, "cannot divide {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot divide {l:#} and {r:#}")
 		}
 	}
 }
@@ -463,7 +153,7 @@ impl Value {
 			(V::Ratio(_x), V::Ratio(_y)) => todo!("ratio modulo"),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x.rem_euclid(y))),
 			(V::Complex(_x), V::Complex(_y)) => todo!("complex modulo"),
-			(l, r) => throw!(type_error, "cannot modulo {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot modulo {l:#} and {r:#}")
 		}
 	}
 
@@ -474,7 +164,7 @@ impl Value {
 			(V::Ratio(_x), V::Ratio(_y)) => todo!("ratio integer division"),
 			(V::Float(x), V::Float(y)) => Ok(V::Float(x.div_euclid(y))),
 			(V::Complex(_x), V::Complex(_y)) => todo!("complex integer division"),
-			(l, r) => throw!(type_error, "cannot integer divide {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot integer divide {l:#} and {r:#}")
 		}
 	}
 
@@ -492,7 +182,7 @@ impl Value {
 				=> Ok(V::Float(ratio_to_f64(x).powf(ratio_to_f64(y)))),
 			(V::Complex(x), V::Complex(y))
 				=> Ok(V::Complex(x.powc(y))),
-			(l, r) => throw!(type_error, "cannot exponentiate {l:#} and {r:#}")
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot exponentiate {l:#} and {r:#}")
 		}
 	}
 }
@@ -501,7 +191,7 @@ impl PartialEq for Value {
 	#[allow(clippy::cast_precision_loss)]
 	fn eq(&self, other: &Self) -> bool {
 		use Value as V;
-		use RangeType as Rty;
+		use super::range::RangeType as Rty;
 		match (self, other) {
 			(V::Nil,        V::Nil) => true,
 			(V::Bool(a),    V::Bool(b)) => a == b,
@@ -565,21 +255,19 @@ impl Value {
 	pub fn val_cmp(&self, other: &Self) -> Result<Ordering> {
 		match self.partial_cmp(other) {
 			Some(o) => Ok(o),
-			None => throw!(type_error, "cannot compare {self:#} and {other:#}"),
+			None => throw!(*SYM_TYPE_ERROR, "cannot compare {self:#} and {other:#}"),
 		}
 	}
 
 	pub fn index(&self, idx: Self) -> Result<Self> {
 		use Value as V;
 		match (self, idx) {
-			(_lhs, V::List(_l)) => todo!("assign index with list"),
-			(_lhs, V::Range(_r)) => todo!("assign index with range"),
 			(V::List(l), V::Int(i)) => {
 				let l = l.borrow();
 				if i >= 0 && (i as usize) < l.len() {
 					Ok(l[i as usize].clone())
 				} else {
-					throw!(index_error, "index {i} out of bounds for list of length {}", l.len())
+					throw!(*SYM_INDEX_ERROR, "index {i} out of bounds for list of length {}", l.len())
 				}
 			},
 			(V::Range(r), V::Int(i)) => {
@@ -588,9 +276,9 @@ impl Value {
 					|| i < r.stop
 					|| (r.ty == RangeType::Closed && i == r.stop)
 				) {
-					Ok(Value::Int(r.start + i))
+					Ok((r.start + i).into())
 				} else {
-					throw!(index_error, "index {i} out of bounds for range {self}")
+					throw!(*SYM_INDEX_ERROR, "index {i} out of bounds for range {self}")
 				}
 			},
 			(V::Table(t), i) => {
@@ -598,7 +286,7 @@ impl Value {
 				let i = i.try_into()?;
 				Ok(t.get(&i).cloned().unwrap_or(Value::Nil))
 			},
-			(col, idx) => throw!(type_error, "cannot index {col:#} with {idx:#}")
+			(col, idx) => throw!(*SYM_TYPE_ERROR, "cannot index {col:#} with {idx:#}")
 		}
 	}
 
@@ -611,7 +299,7 @@ impl Value {
 					l[i as usize] = val;
 					Ok(())
 				} else {
-					throw!(index_error, "index {i} out of bounds for list of length {}", l.len())
+					throw!(*SYM_INDEX_ERROR, "index {i} out of bounds for list of length {}", l.len())
 				}
 			},
 			(V::Table(t), i) => {
@@ -620,7 +308,7 @@ impl Value {
 				t.insert(i, val);
 				Ok(())
 			},
-			(col, idx) => throw!(index_error, "cannot index {col:#} with {idx:#}")
+			(col, idx) => throw!(*SYM_INDEX_ERROR, "cannot index {col:#} with {idx:#}")
 		}
 	}
 
@@ -630,31 +318,48 @@ impl Value {
 			(V::List(l1), V::List(l2)) => {
 				let mut l = l1.borrow().clone();
 				l.extend_from_slice(&l2.borrow());
-				Ok(V::List(Rc::new(RefCell::new(l))))
+				Ok(l.into())
 			},
 			(V::String(s1), V::String(s2)) => {
 				let mut s = s1.as_ref().to_owned();
 				s.push_str(s2);
 				Ok(V::String(s.into()))
 			}
-			(l, r) => throw!(type_error, "cannot concatenate {l:#} and {r:#}"),
+			(V::Table(t1), V::Table(t2)) => {
+				let mut t = t1.borrow().clone();
+				t.extend(t2.borrow().iter().map(|(k, v)| (k.clone(), v.clone())));
+				Ok(t.into())
+			}
+			(l, r) => throw!(*SYM_TYPE_ERROR, "cannot concatenate {l:#} and {r:#}"),
 		}
 	}
 
+    pub fn append(&self, val: Self) -> Result<Self> {
+		use Value as V;
+		match self {
+			V::List(list) => {
+				let mut l = list.borrow().clone();
+				l.push(val);
+				Ok(l.into())
+			},
+			lhs => throw!(*SYM_TYPE_ERROR, "cannot append to {lhs:#}"),
+        }
+    }
+
 	pub fn range(&self, other: &Self, closed: bool) -> Result<Self> {
 		if let (Value::Int(start), Value::Int(stop)) = (self, other) {
 			let ty = if closed { RangeType::Closed } else { RangeType::Open };
-			Ok(Value::Range(Range { start: *start, stop: *stop, ty }))
+			Ok(Range { start: *start, stop: *stop, ty }.into())
 		} else {
-			throw!(type_error, "cannot create range between {self:#} and {other:#}")
+			throw!(*SYM_TYPE_ERROR, "cannot create range between {self:#} and {other:#}")
 		}
 	}
 
 	pub fn range_endless(&self) -> Result<Self> {
 		if let Value::Int(start) = self {
-			Ok(Value::Range(Range { start: *start, stop: 0, ty: RangeType::Endless }))
+			Ok(Range { start: *start, stop: 0, ty: RangeType::Endless }.into())
 		} else {
-			throw!(type_error, "cannot create endless range from {self:#}")
+			throw!(*SYM_TYPE_ERROR, "cannot create endless range from {self:#}")
 		}
 	}
 
@@ -663,50 +368,50 @@ impl Value {
 			Self::Function(_) | Self::NativeFunc(_) => Ok(self),
 			Self::Range(range) => {
 				let range_iter = RefCell::new(range.into_iter());
-				let f = move |_, _| {
+				let f = move |_: &mut Vm, _: Vec<Value>| -> Result<Value> {
 					if let Some(v) = range_iter.borrow_mut().next() {
-						Ok(Value::Int(v))
+						Ok(v.into())
 					} else {
-						Ok(Value::Nil)
+                        throw!(*SYM_STOP_ITERATOR)
 					}
 				};
-				Ok(Value::NativeFunc(Rc::new(NativeFunc {
+				Ok(NativeFunc {
 					arity: 0,
-					f: Box::new(f),
-				})))
+				    f: Box::new(f),
+				}.into())
 			},
 			Self::List(list) => {
 				let idx = RefCell::new(0);
-				let f = move |_, _| {
+				let f = move |_: &mut Vm, _: Vec<Value>| -> Result<Value> {
 					let i = *idx.borrow();
 					if let Some(v) = list.borrow().get(i) {
 						*idx.borrow_mut() += 1;
 						Ok(v.clone())
 					} else {
-						Ok(Value::Nil)
+                        throw!(*SYM_STOP_ITERATOR)
 					}
 				};
-				Ok(Value::NativeFunc(Rc::new(NativeFunc {
+				Ok(NativeFunc {
 					arity: 0,
 					f: Box::new(f),
-				})))
+				}.into())
 			},
 			Self::Table(table) => {
 				let keys: Vec<HashValue> = table.borrow().keys().cloned().collect();
 				let keys = RefCell::new(keys.into_iter());
-				let f = move |_, _| {
+				let f = move |_: &mut Vm, _: Vec<Value>| -> Result<Value> {
 					if let Some(v) = keys.borrow_mut().next() {
 						Ok(v.into_inner())
 					} else {
-						Ok(Value::Nil)
+                        throw!(*SYM_STOP_ITERATOR)
 					}
 				};
-				Ok(Value::NativeFunc(Rc::new(NativeFunc {
+				Ok(NativeFunc {
 					arity: 0,
 					f: Box::new(f),
-				})))
+				}.into())
 			},
-			_ => throw!(type_error, "cannot iterate {self:#}"),
+			_ => throw!(*SYM_TYPE_ERROR, "cannot iterate {self:#}"),
 		}
 	}
 }
diff --git a/talc-lang/src/value/range.rs b/talc-lang/src/value/range.rs
new file mode 100644
index 0000000..8597a6a
--- /dev/null
+++ b/talc-lang/src/value/range.rs
@@ -0,0 +1,43 @@
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RangeType {
+	Open, Closed, Endless,
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct Range {
+	pub start: i64,
+	pub stop: i64,
+	pub ty: RangeType,
+}
+
+impl Range {
+	pub fn len(&self) -> Option<usize> {
+		match self.ty {
+			RangeType::Open => Some((self.stop - self.start).max(0) as usize),
+			RangeType::Closed => Some((self.stop - self.start + 1).max(0) as usize),
+			RangeType::Endless => None,
+		}
+	}
+
+	pub fn is_empty(&self) -> bool {
+		match self.ty {
+			RangeType::Open => self.stop - self.start <= 0,
+			RangeType::Closed => self.stop - self.start < 0,
+			RangeType::Endless => false,
+		}
+	}
+}
+
+impl IntoIterator for Range {
+	type Item = i64;
+	type IntoIter = Box<dyn Iterator<Item=i64>>;
+	fn into_iter(self) -> Self::IntoIter {
+		match self.ty {
+			RangeType::Open => Box::new(self.start..self.stop),
+			RangeType::Closed => Box::new(self.start..=self.stop),
+			RangeType::Endless => Box::new(self.start..),
+		}
+	}
+}
+
diff --git a/talc-lang/src/vm.rs b/talc-lang/src/vm.rs
index 8e55b42..1ec7071 100644
--- a/talc-lang/src/vm.rs
+++ b/talc-lang/src/vm.rs
@@ -1,6 +1,6 @@
-use std::{rc::Rc, cmp::Ordering, cell::RefCell, collections::HashMap};
+use std::{cmp::Ordering, collections::HashMap, rc::Rc, sync::{atomic::AtomicBool, Arc}};
 
-use crate::{chunk::Instruction, value::{Value, Function, Result, throw, Exception}, ast::{BinaryOp, UnaryOp}, symbol::Symbol};
+use crate::{ast::{BinaryOp, UnaryOp}, chunk::Instruction, symbol::{Symbol, SYM_CALL_STACK_OVERFLOW, SYM_INTERRUPTED, SYM_NAME_ERROR, SYM_TYPE_ERROR}, value::{exception::{throw, Exception, Result}, function::Function, Value}};
 
 struct TryFrame { idx: usize, stack_len: usize }
 
@@ -13,7 +13,6 @@ struct CallFrame {
 	root: bool,
 }
 
-
 impl CallFrame {
 	fn new(func: Rc<Function>, locals: Vec<Value>) -> Self {
 		Self {
@@ -22,15 +21,6 @@ impl CallFrame {
 			..Self::default()
 		}
 	}
-
-	fn new_root(func: Rc<Function>) -> Self {
-		Self {
-			func: func.clone(),
-			locals: vec![Value::Function(func)],
-			root: true,
-			..Self::default()
-		}
-	}
 }
 
 pub struct Vm {
@@ -38,6 +28,7 @@ pub struct Vm {
 	call_stack: Vec<CallFrame>,
 	stack_max: usize,
 	globals: HashMap<Symbol, Value>,
+    interrupt: Arc<AtomicBool>,
 }
 
 pub fn binary_op(o: BinaryOp, a: Value, b: Value) -> Result<Value> {
@@ -58,7 +49,7 @@ pub fn binary_op(o: BinaryOp, a: Value, b: Value) -> Result<Value> {
 		BinaryOp::Range => a.range(&b, false),
 		BinaryOp::RangeIncl => a.range(&b, true),
 		BinaryOp::Concat => a.concat(&b),
-		BinaryOp::Append => todo!("append"),
+		BinaryOp::Append => a.append(b),
 	}
 }
 
@@ -77,13 +68,22 @@ impl Vm {
 			call_stack: Vec::with_capacity(16),
 			globals: HashMap::with_capacity(16),
 			stack_max,
+            interrupt: Arc::new(AtomicBool::new(false)),
 		}
 	}
 
+    pub fn get_interrupt(&self) -> Arc<AtomicBool> {
+        self.interrupt.clone()
+    }
+
 	pub fn set_global(&mut self, name: Symbol, val: Value) {
 		self.globals.insert(name, val);
 	}
 
+	pub fn set_global_name(&mut self, name: &str, val: Value) {
+		self.globals.insert(Symbol::get(name), val);
+	}
+
 	pub fn get_global(&self, name: Symbol) -> Option<&Value> {
 		self.globals.get(&name)
 	}
@@ -105,68 +105,91 @@ impl Vm {
 		res
 	}
 
-	fn debug_instr(&self, frame: &CallFrame, instr: Instruction) {
-		let framecode = (Rc::as_ptr(&frame.func) as usize >> 4) & 0xffff;
-		println!("({:04x}) {:04}: {instr}", framecode, frame.ip);
-	}
+    fn check_interrupt(&mut self) -> Result<()> {
+        if self.interrupt.fetch_and(false, std::sync::atomic::Ordering::Relaxed) {
+            throw!(*SYM_INTERRUPTED)
+        }
+        Ok(())
+    }
 
 	fn run_instr(&mut self, frame: &mut CallFrame, instr: Instruction) -> Result<Option<Value>> {
 		use Instruction as I;
+
 		match instr {
+            // do nothing
 			I::Nop => (),
+            // [] -> [locals[n]]
 			I::LoadLocal(n)
 				=> self.push(frame.locals[usize::from(n)].clone()),
+            // [x] -> [], locals[n] = x
 			I::StoreLocal(n)
 				=> frame.locals[usize::from(n)] = self.pop(),
+            // [x] -> [], locals.push(x)
 			I::NewLocal
 				=> frame.locals.push(self.pop()),
+            // locals.pop_n(n)
 			I::DropLocal(n)
 				=> frame.locals.truncate(frame.locals.len() - usize::from(n)),
+            // [] -> [globals[s]]
 			I::LoadGlobal(s) => {
 				let sym = unsafe { s.to_symbol_unchecked() };
 				let v = match self.globals.get(&sym) {
 					Some(v) => v.clone(),
-					None => throw!(name_error, "undefined global {}", sym.name()),
+					None => throw!(*SYM_NAME_ERROR, "undefined global {}", sym.name()),
 				};
 				self.push(v);
 			},
+            // [x] -> [], globals[s] = x
 			I::StoreGlobal(s) => {
 				let sym = unsafe { s.to_symbol_unchecked() };
 				let v = self.pop();
 				self.globals.insert(sym, v);
 			},
+            // [] -> [consts[n]]
 			I::Const(n)
 				=> self.push(frame.func.chunk.consts[usize::from(n)].clone()),
+            // [] -> [nil]
 			I::Nil => self.push(Value::Nil),
+            // [] -> [b]
 			I::Bool(b) => self.push(Value::Bool(b)),
-			I::Symbol(n) => {
-				let sym = unsafe { Symbol::from_id_unchecked(u32::from(n)) };
+            // [] -> [s]
+			I::Symbol(s) => {
+				let sym = unsafe { Symbol::from_id_unchecked(u32::from(s)) };
 				self.push(Value::Symbol(sym));
 			},
+            // [] -> [n]
 			I::Int(n) => self.push(Value::Int(i64::from(n))),
+            // [x] -> [x,x]
 			I::Dup => self.push(self.stack[self.stack.len() - 1].clone()),
+            // [x,y] -> [x,y,x,y]
 			I::DupTwo => {
 				self.push(self.stack[self.stack.len() - 2].clone());
 				self.push(self.stack[self.stack.len() - 2].clone());
 			},
+            // [a0,a1...an] -> []
 			I::Drop(n) => for _ in 0..u32::from(n) { self.pop(); },
+            // [x,y] -> [y,x]
 			I::Swap => {
 				let len = self.stack.len();
 				self.stack.swap(len - 1, len - 2);
 			},
+            // [x,y] -> [y op x]
 			I::BinaryOp(op) => {
 				let b = self.pop();
 				let a = self.pop();
 				self.push(binary_op(op, a, b)?);
 			},
+            // [x] -> [op x]
 			I::UnaryOp(op) => {
 				let a = self.pop();
 				self.push(unary_op(op, a)?);
 			},
+            // [a0,a1...an] -.> [[a0,a1...an]]
 			I::NewList(n) => {
 				let list = self.pop_n(n as usize);
-				self.push(Value::List(Rc::new(RefCell::new(list))));
+				self.push(list.into())
 			},
+            // [l,a0,a1...an] -.> [l ++ [a0,a1...an]]
 			I::GrowList(n) => {
 				let ext = self.pop_n(n as usize);
 				let list = self.pop();
@@ -174,6 +197,7 @@ impl Vm {
 				list.borrow_mut().extend(ext);
 				self.push(Value::List(list));
 			},
+            // [k0,v0...kn,vn] -.> [{k0=v0...kn=vn}]
 			I::NewTable(n) => {
 				let mut table = HashMap::new();
 				for _ in 0..n {
@@ -181,8 +205,9 @@ impl Vm {
 					let k = self.pop();
 					table.insert(k.try_into()?, v);
 				}
-				self.push(Value::Table(Rc::new(RefCell::new(table))));
+				self.push(table.into())
 			},
+            // [t,k0,v0...kn,vn] -> [t ++ {k0=v0...kn=vn}]
 			I::GrowTable(n) => {
 				let mut ext = self.pop_n(2 * n as usize);
 				let table = self.pop();
@@ -197,11 +222,13 @@ impl Vm {
 				drop(table_ref);
 				self.push(Value::Table(table));
 			},
+            // [ct, idx] -> [ct!idx]
 			I::Index => {
 				let idx = self.pop();
 				let ct = self.pop();
 				self.push(ct.index(idx)?);
 			},
+            // [ct, idx, v] -> [v], ct!idx = v
 			I::StoreIndex => {
 				let v = self.pop();
 				let idx = self.pop();
@@ -209,21 +236,43 @@ impl Vm {
 				ct.store_index(idx, v.clone())?;
 				self.push(v);
 			},
-			I::Jump(n) => frame.ip = usize::from(n),
-			I::JumpTrue(n)  => if self.pop().truthy() { frame.ip = usize::from(n) },
-			I::JumpFalse(n) => if !self.pop().truthy() { frame.ip = usize::from(n) },
+            // ip = n
+			I::Jump(n) => {
+                self.check_interrupt()?;
+                frame.ip = usize::from(n)
+            },
+            // [v] ->, [], if v then ip = n
+			I::JumpTrue(n)  => if self.pop().truthy() { 
+                self.check_interrupt()?;
+                frame.ip = usize::from(n)
+            },
+            // [v] ->, [], if not v then ip = n
+			I::JumpFalse(n) => if !self.pop().truthy() { 
+                self.check_interrupt()?;
+                frame.ip = usize::from(n)
+            },
+            // [v] -> [iter(v)]
 			I::IterBegin => {
 				let iter = self.pop().to_iter_function()?;
 				self.push(iter);
 			},
-			I::IterTest(n) => {
+            // [i] -> if i() succeeds then [i, i()], otherwise [] and ip = n
+			I::IterNext(n) => {
 				let v = &self.stack[self.stack.len() - 1];
-				if v == &Value::Nil {
-					self.pop();
-					self.pop();
-					frame.ip = usize::from(n);
-				}
+                self.call_stack.push(std::mem::take(frame));
+                let res = self.call_value(v.clone(), vec![v.clone()]);
+                *frame = self.call_stack.pop().expect("no frame to pop");
+                match res {
+                    Ok(res) => self.push(res),
+                    Err(e) => if e.ty == Symbol::get("stop_iterator") {
+                        self.pop();
+                        frame.ip = usize::from(n)
+                    } else {
+                        return Err(e)
+                    }
+                }
 			},
+            // try_frames.push(t, stack.len())
 			I::BeginTry(t) => {
 				let tryframe = TryFrame {
 					idx: usize::from(t),
@@ -231,48 +280,48 @@ impl Vm {
 				};
 				frame.try_frames.push(tryframe);
 			},
+            // try_frames.pop()
 			I::EndTry => {
 				frame.try_frames.pop().expect("no try to pop");
 			},
+            // [f,a0,a1...an] -> [f(a0,a1...an)]
 			I::Call(n) => {
+                self.check_interrupt()?;
 				let n = usize::from(n);
-				let func = &self.stack[self.stack.len() - n - 1];
+                let args = self.pop_n(n + 1);
+				let func = &args[0];
 				if let Value::NativeFunc(nf) = func {
 					let nf = nf.clone();
 					if nf.arity != n {
-						throw!(type_error, "function call with wrong argument count");
+						throw!(*SYM_TYPE_ERROR, "function call with wrong argument count");
 					}
 
-					let args = self.pop_n(n);
-					let func = self.pop();
-
 					self.call_stack.push(std::mem::take(frame));
-					let res = (nf.f)(func, args)?;
-					*frame = self.call_stack.pop().expect("no frame left on stack");
+					let res = (nf.f)(self, args)?;
+					*frame = self.call_stack.pop().expect("no frame to pop");
 
 					self.stack.push(res);
 				} else if let Value::Function(func) = func {
 					if func.arity != n {
-						throw!(type_error, "function call with wrong argument count");
+						throw!(*SYM_TYPE_ERROR, "function call with wrong argument count");
 					}
 
 					if self.call_stack.len() + 1 >= self.stack_max {
-						throw!(call_stack_overflow, "call stack overflow")
+						throw!(*SYM_CALL_STACK_OVERFLOW, "call stack overflow")
 					}
 					self.call_stack.push(std::mem::take(frame));
 
 					let func = func.clone();
-					let args = self.pop_n(n + 1);
 					*frame = CallFrame::new(func, args);
 				} else {
-					throw!(type_error, "attempt to call non-function {func}");
+					throw!(*SYM_TYPE_ERROR, "attempt to call non-function {func}");
 				}
 			},
+            // [v] -> [], return v
 			I::Return if frame.root => {
-				let v = self.pop();
-				self.stack.clear();
-				return Ok(Some(v));
+				return Ok(Some(self.pop()));
 			},
+            // [v] -> [], return v
 			I::Return => {
 				*frame = self.call_stack.pop().expect("no root frame");
 			},
@@ -302,14 +351,34 @@ impl Vm {
 		}
 	}
 
-	pub fn run(&mut self, func: Rc<Function>) -> Result<Value> {
-		assert!(func.arity == 0, "root function must not take arguments");
+    pub fn call_value(&mut self, value: Value, args: Vec<Value>) -> Result<Value> {
+        match value {
+            Value::Function(f) => self.call(f, args),
+            Value::NativeFunc(f) => {
+                if f.arity + 1 != args.len() {
+                    throw!(*SYM_TYPE_ERROR, "function call with wrong argument count");
+                }
+                (f.f)(self, args)
+            },
+            _ => throw!(*SYM_TYPE_ERROR, "not a function"),
+        }
+    }
+
+
+    pub fn call_no_args(&mut self, func: Rc<Function>) -> Result<Value> {
+        self.call(func.clone(), vec![func.into()])
+    }
+
+	pub fn call(&mut self, func: Rc<Function>, args: Vec<Value>) -> Result<Value> {
+        if func.arity + 1 != args.len() {
+            throw!(*SYM_TYPE_ERROR, "function call with wrong argument count");
+        }
 		let init_stack_len = self.stack.len();
-		let mut frame = CallFrame::new_root(func.clone());
+		let mut frame = CallFrame::new(func, args);
+        frame.root = true;
 
 		loop {
 			let instr = frame.func.chunk.instrs[frame.ip];
-			self.debug_instr(&frame, instr);
 			frame.ip += 1;
 			match self.run_instr(&mut frame, instr) {
 				Ok(None) => (),
diff --git a/talc-macros/Cargo.toml b/talc-macros/Cargo.toml
new file mode 100644
index 0000000..a7d44c4
--- /dev/null
+++ b/talc-macros/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "talc-macros"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "1.0", features = ["full"] }
+quote = "1.0"
diff --git a/talc-macros/src/lib.rs b/talc-macros/src/lib.rs
new file mode 100644
index 0000000..46c8bfc
--- /dev/null
+++ b/talc-macros/src/lib.rs
@@ -0,0 +1,32 @@
+use proc_macro::TokenStream;
+use syn::{LitInt, ItemFn};
+use quote::quote;
+
+#[proc_macro_attribute]
+pub fn native_func(input: TokenStream, annotated_item: TokenStream) -> TokenStream {
+    let itemfn: ItemFn = syn::parse(annotated_item).unwrap();
+    let arity: LitInt = syn::parse(input).unwrap();
+
+    let visibility = itemfn.vis;
+    let block = itemfn.block;
+    let name = itemfn.sig.ident;
+    let inputs = itemfn.sig.inputs;
+    let output = itemfn.sig.output;
+
+    assert!(itemfn.sig.constness.is_none(), "item must not be const");
+    assert!(itemfn.sig.asyncness.is_none(), "item must not be async");
+    assert!(itemfn.sig.unsafety.is_none(), "item must not be unsafe");
+    assert!(itemfn.sig.abi.is_none(), "item must not contain an ABI specifier");
+    assert!(itemfn.sig.variadic.is_none(), "item must not be variadic");
+
+    let expanded = quote! {
+        #visibility fn #name() -> ::talc_lang::value::function::NativeFunc {
+            ::talc_lang::value::function::NativeFunc {
+                arity: #arity,
+                f: Box::new(|#inputs| #output #block)
+            }
+        }
+    };
+    
+    TokenStream::from(expanded)
+}
diff --git a/talc-std/Cargo.toml b/talc-std/Cargo.toml
index d2ed7c0..81e3fb8 100644
--- a/talc-std/Cargo.toml
+++ b/talc-std/Cargo.toml
@@ -4,3 +4,6 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+talc-lang = { path = "../talc-lang" }
+talc-macros = { path = "../talc-macros" }
+lazy_static = "1.4"
diff --git a/talc-std/src/exception.rs b/talc-std/src/exception.rs
new file mode 100644
index 0000000..1e5874c
--- /dev/null
+++ b/talc-std/src/exception.rs
@@ -0,0 +1,31 @@
+use talc_lang::{symbol::SYM_TYPE_ERROR, value::{exception::{throw, Exception, Result}, Value}, Vm};
+use talc_macros::native_func;
+
+#[native_func(2)]
+pub fn throw(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    let [_, ty, msg] = args.try_into().expect("bypassed arity check");
+    let Value::Symbol(ty) = ty else {
+        throw!(*SYM_TYPE_ERROR, "exception type must be a symbol")
+    };
+    match msg {
+        Value::String(msg) => Err(Exception::new_with_msg(ty, msg)),
+        Value::Nil => Err(Exception::new(ty)),
+        _ => throw!(*SYM_TYPE_ERROR, "exception message must be a string")
+    }
+}
+
+#[native_func(1)]
+pub fn rethrow(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    let [_, table] = args.try_into().expect("bypassed arity check");
+    if let Value::Table(table) = table {
+        if let Some(e) = Exception::from_table(&table) {
+            return Err(e)
+        }
+    }
+    throw!(*SYM_TYPE_ERROR, "argument not a valid exception")
+}
+
+pub fn load(vm: &mut Vm) {
+    vm.set_global_name("throw", throw().into());
+    vm.set_global_name("rethrow", rethrow().into());
+}
diff --git a/talc-std/src/io.rs b/talc-std/src/io.rs
new file mode 100644
index 0000000..7bdec38
--- /dev/null
+++ b/talc-std/src/io.rs
@@ -0,0 +1,37 @@
+use std::io::Write;
+
+use talc_lang::{value::{exception::{throw, Result}, Value}, Vm};
+use talc_macros::native_func;
+
+use crate::SYM_IO_ERROR;
+
+#[native_func(1)]
+pub fn print(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    if let Err(e) = write!(std::io::stdout(), "{}", args[1]) {
+        throw!(*SYM_IO_ERROR, "{e}")
+    }
+    Ok(Value::Nil)
+}
+
+#[native_func(1)]
+pub fn println(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    if let Err(e) = writeln!(std::io::stdout(), "{}", args[1]) {
+        throw!(*SYM_IO_ERROR, "{e}")
+    }
+    Ok(Value::Nil)
+}
+
+#[native_func(0)]
+pub fn readln(_: &mut Vm, _: Vec<Value>) -> Result<Value> {
+    let mut buf = String::new();
+    if let Err(e) = std::io::stdin().read_line(&mut buf) {
+        throw!(*SYM_IO_ERROR, "{e}")
+    }
+    Ok(buf.into())
+}
+
+pub fn load(vm: &mut Vm) {
+    vm.set_global_name("print", print().into());
+    vm.set_global_name("println", println().into());
+    vm.set_global_name("readln", readln().into());
+}
diff --git a/talc-std/src/iter.rs b/talc-std/src/iter.rs
new file mode 100644
index 0000000..41b4c9e
--- /dev/null
+++ b/talc-std/src/iter.rs
@@ -0,0 +1,42 @@
+use talc_lang::{symbol::SYM_STOP_ITERATOR, value::{exception::Result, function::NativeFunc, Value}, Vm};
+use talc_macros::native_func;
+
+#[native_func(1)]
+pub fn iter(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    let [_, v] = args.try_into().expect("bypassed arity check");
+    v.to_iter_function()
+}
+
+#[native_func(2)]
+pub fn map(_: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    let [_, func, iter] = args.try_into().expect("bypassed arity check");
+    let iter = iter.to_iter_function()?;
+    let f = move |vm: &mut Vm, _| {
+        let next = vm.call_value(iter.clone(), vec![iter.clone()])?;
+        vm.call_value(func.clone(), vec![func.clone(), next])
+    };
+    Ok(NativeFunc { arity: 0, f: Box::new(f) }.into())
+}
+
+#[native_func(1)]
+pub fn list(vm: &mut Vm, args: Vec<Value>) -> Result<Value> {
+    let [_, iter] = args.try_into().expect("bypassed arity check");
+    let iter = iter.to_iter_function()?;
+    let mut result = Vec::new();
+    loop {
+        match vm.call_value(iter.clone(), vec![iter.clone()]) {
+            Ok(v) => result.push(v),
+            Err(e) => if e.ty == *SYM_STOP_ITERATOR {
+                return Ok(result.into())
+            } else {
+                return Err(e)
+            }
+        }
+    };
+}
+
+pub fn load(vm: &mut Vm) {
+    vm.set_global_name("iter", iter().into());
+    vm.set_global_name("map", map().into());
+    vm.set_global_name("list", list().into());
+}
diff --git a/talc-std/src/lib.rs b/talc-std/src/lib.rs
index e69de29..2856dee 100644
--- a/talc-std/src/lib.rs
+++ b/talc-std/src/lib.rs
@@ -0,0 +1,17 @@
+use talc_lang::{symbol::{symbol, Symbol}, Vm};
+
+pub mod num;
+pub mod io;
+pub mod iter;
+pub mod exception;
+
+pub fn load_all(vm: &mut Vm) {
+    num::load(vm);
+    io::load(vm);
+    iter::load(vm);
+    exception::load(vm);
+}
+
+lazy_static::lazy_static! {
+    pub static ref SYM_IO_ERROR: Symbol = symbol!(io_error);
+}
diff --git a/talc-std/src/num.rs b/talc-std/src/num.rs
new file mode 100644
index 0000000..9e6fec5
--- /dev/null
+++ b/talc-std/src/num.rs
@@ -0,0 +1,5 @@
+use talc_lang::Vm;
+
+pub fn load(vm: &mut Vm) {
+
+}