diff --git a/example/data/hello_world.mc b/example/data/hello_world.mc
new file mode 100644
index 0000000..d346023
--- /dev/null
+++ b/example/data/hello_world.mc
@@ -0,0 +1,4 @@
+
+let msg = "hello world";
+
+msg
\ No newline at end of file
diff --git a/example/data/loops.mc b/example/data/loops.mc
new file mode 100644
index 0000000..1aaa011
--- /dev/null
+++ b/example/data/loops.mc
@@ -0,0 +1,22 @@
+
+let i = 0;
+
+loop {
+    i = i + 1;
+    print("i", i);
+    if (i > 5) break;
+}
+
+fn for(array, op) {
+    let index = 0;
+    loop {
+        let item = array[index];
+        if (item == none) break;
+        op(item, index);
+        index = index + 1;
+    }
+}
+
+for([1, 2, 3], (item, index) => {
+    print("at index", index, "item", item);
+});
diff --git a/example/run.rs b/example/run.rs
index 02e2eb8..0c08864 100644
--- a/example/run.rs
+++ b/example/run.rs
@@ -1,15 +1,21 @@
 use std::{env::args, fs};
 
-use microlang::Context;
+use microlang::{Context, Value};
 
 pub fn main() {
 	unsafe { backtrace_on_stack_overflow::enable() };
 	let mut context = Context::empty();
-	let lines = fs::read_to_string(args().nth(1).expect("Pass a file as arg 1.")).expect("File could not be read.");
-	for line in lines.lines() {
-		match context.eval(line.into()) {
-			Err(err) => panic!("Failed : {err:?}"),
-			Ok((_, value)) => println!("{}", value.serialize()),
+	context.define_built("print", |values, _| {
+		for val in values {
+			print!("{} ", val.serialize());
 		}
+		println!();
+		Ok(Value::None)
+	});
+
+	let lines = fs::read_to_string(args().nth(1).expect("Pass a file as arg 1.")).expect("File could not be read.");
+	match context.eval(lines) {
+		Err(err) => panic!("Failed : {err:?}"),
+		Ok((_, value)) => println!("{}", value.serialize()),
 	}
 }
diff --git a/src/ast.rs b/src/ast.rs
index 0fa4fab..aa16224 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -6,7 +6,7 @@ use crate::{util::Boxable, Context, EvalError, FunImpl, Function, Value};
 use chumsky::{
 	error::Simple,
 	prelude::{end, just, none_of, one_of, recursive, Recursive},
-	text::{whitespace, TextParser},
+	text::TextParser,
 	Parser,
 };
 use hashbrown::HashMap;
@@ -17,10 +17,7 @@ pub trait Parse<O>: Parser<char, O, Error = Simple<char>> + Clone + 'static {}
 impl<T: Parser<char, O, Error = Simple<char>> + Clone + 'static, O> Parse<O> for T {}
 
 fn lx(word: &'static str) -> impl Parse<&'static str> {
-	whitespace()
-		.ignore_then(just(word))
-		.then_ignore(whitespace())
-		.labelled("token")
+	just(word).padded().labelled("token")
 }
 
 fn id() -> impl Parse<String> {
@@ -41,8 +38,6 @@ pub struct Block {
 impl Block {
 	pub fn parser(instr: impl Parse<Instr>, expr: impl Parse<Expr>) -> impl Parse<Self> {
 		instr
-			.clone()
-			.then_ignore(lx(";"))
 			.repeated()
 			.then(expr.map(Boxable::to_box).or_not())
 			.map(|(instructions, expression)| Self {
@@ -97,6 +92,7 @@ impl FunDef {
 	pub fn parser_lamb(instr: impl Parse<Instr>, expr: impl Parse<Expr>) -> impl Parse<Self> {
 		let arguments = id().padded().separated_by(lx(","));
 		(lx("(").ignore_then(arguments).then_ignore(lx(")")))
+			.then_ignore(lx("=>"))
 			.then(lx("{").ignore_then(Block::parser(instr, expr)).then_ignore(lx("}")))
 			.map(|(args, body)| Self { args, body })
 			.labelled("lambda")
@@ -121,38 +117,42 @@ pub enum Instr {
 impl Instr {
 	pub fn parser(expr: impl Parse<Expr>) -> impl Parse<Self> {
 		recursive(|instr: Recursive<'_, _, Self, _>| {
-			(lx("{")
-				.ignore_then(Block::parser(instr.clone(), expr.clone()))
-				.then_ignore(lx("}"))
-				.map(Self::Block))
-			.labelled("block instruction")
-			.or(lx("let")
-				.ignore_then(id())
-				.then_ignore(lx("="))
-				.then(expr.clone())
-				.map(|(id, ex)| Self::Init(id, ex)))
-			.labelled("variable initialization")
-			.or(lx("if")
-				.ignore_then(lx("(").ignore_then(expr.clone()).then_ignore(lx(")")))
-				.then((instr.clone()).then((lx("else").ignore_then(instr.clone())).or_not()))
-				.map(|(cond, (then, els))| Self::Branch(cond, then.to_box(), els.unwrap_or(Instr::Nop).to_box())))
-			.labelled("condition instruction")
-			.or(lx("loop")
-				.ignore_then(instr.clone())
-				.map(|body| Self::Loop(body.to_box())))
-			.labelled("loop instruction")
-			.or(ShortDef::parser(expr.clone())
-				.map(Self::Short)
-				.labelled("shortcut instruction"))
-			.or(FunDef::parser_def(instr, expr.clone())
-				.map(|(name, fun)| Self::FnDef(name, fun))
-				.labelled("function definition"))
-			.or(id()
-				.then_ignore(lx("="))
-				.then(expr.clone())
-				.map(|(id, ex)| Self::Assign(id, ex))
-				.labelled("variable assigniation."))
-			.or(expr.map(Self::Expr))
+			(lx(";").map(|_| Self::Nop).labelled("no operation"))
+				.or(lx("{")
+					.ignore_then(Block::parser(instr.clone(), expr.clone()))
+					.then_ignore(lx("}"))
+					.map(Self::Block)
+					.labelled("block instruction"))
+				.or(lx("let")
+					.ignore_then(id())
+					.then_ignore(lx("="))
+					.then(expr.clone())
+					.then_ignore(lx(";"))
+					.map(|(id, ex)| Self::Init(id, ex))
+					.labelled("variable initialization"))
+				.or(lx("if")
+					.ignore_then(lx("(").ignore_then(expr.clone()).then_ignore(lx(")")))
+					.then((instr.clone()).then((lx("else").ignore_then(instr.clone())).or_not()))
+					.map(|(cond, (then, els))| Self::Branch(cond, then.to_box(), els.unwrap_or(Instr::Nop).to_box()))
+					.labelled("condition instruction"))
+				.or(lx("loop")
+					.ignore_then(instr.clone())
+					.map(|body| Self::Loop(body.to_box()))
+					.labelled("loop instruction"))
+				.or(ShortDef::parser(expr.clone())
+					.then_ignore(lx(";"))
+					.map(Self::Short)
+					.labelled("shortcut instruction"))
+				.or(FunDef::parser_def(instr, expr.clone())
+					.map(|(name, fun)| Self::FnDef(name, fun))
+					.labelled("function definition"))
+				.or(id()
+					.then_ignore(lx("="))
+					.then(expr.clone())
+					.then_ignore(lx(";"))
+					.map(|(id, ex)| Self::Assign(id, ex))
+					.labelled("variable assigniation"))
+				.or(expr.then_ignore(lx(";")).map(Self::Expr))
 		})
 		.labelled("instruction")
 	}
@@ -164,7 +164,7 @@ impl Instr {
 			Self::Expr(expr) => no_short(expr.eval(context)?),
 			Self::Init(name, expr) => {
 				let value = expr.eval(context)?;
-				context.scope().borrow_mut().append(name.clone(), value);
+				context.scope().borrow_mut().define(name.clone(), value);
 				no_short(())
 			}
 			Self::Assign(name, expr) => {
@@ -262,7 +262,7 @@ impl Expr {
 				.map(|(e, a)| Self::Access(e.to_box(), a)))
 			.or((left.clone())
 				.then_ignore(lx("("))
-				.then(expr.clone().then_ignore(lx(",")).repeated())
+				.then(expr.clone().separated_by(lx(",")))
 				.then_ignore(lx(")"))
 				.map(|(e, a)| Self::Call(e.to_box(), a)))
 			.or((left.clone())
@@ -354,6 +354,21 @@ impl Op {
 		Ok(match (self, l, r) {
 			(Self::Add, Value::Str(l), Value::Str(r)) => Value::Str(format!("{l}{r}")),
 			(Self::Add, Value::Num(l), Value::Num(r)) => Value::Num(l + r),
+			(Self::Sub, Value::Num(l), Value::Num(r)) => Value::Num(l - r),
+			(Self::Div, Value::Num(l), Value::Num(r)) => Value::Num(l / r),
+			(Self::Prod, Value::Num(l), Value::Num(r)) => Value::Num(l * r),
+			(Self::Lt, Value::Num(l), Value::Num(r)) => Value::Bool(l < r),
+			(Self::Gt, Value::Num(l), Value::Num(r)) => Value::Bool(l > r),
+			(Self::Leq, Value::Num(l), Value::Num(r)) => Value::Bool(l <= r),
+			(Self::Geq, Value::Num(l), Value::Num(r)) => Value::Bool(l >= r),
+			(Self::Eq, Value::None, Value::None) => Value::Bool(true),
+			(Self::Eq, Value::Num(l), Value::Num(r)) => Value::Bool(l == r),
+			(Self::Eq, Value::Str(l), Value::Str(r)) => Value::Bool(l == r),
+			(Self::Eq, Value::Array(l), Value::Array(r)) => Value::Bool(Rc::ptr_eq(l, r)),
+			(Self::Eq, Value::Object(l), Value::Object(r)) => Value::Bool(Rc::ptr_eq(l, r)),
+			(Self::Eq, Value::Function(l), Value::Function(r)) => Value::Bool(Rc::ptr_eq(l, r)),
+			(Self::Eq, _, _) => Value::Bool(false),
+			(Self::Neq, _, _) => UniOp::Inv.apply(&Self::Eq.apply(l, r)?)?,
 			_ => Err(EvalError::WrongType)?,
 		})
 	}
@@ -400,6 +415,7 @@ impl Litteral {
 			.ignore_then(char.repeated())
 			.then_ignore(just("\""))
 			.map(|s| Self::Str(s.iter().collect())))
+		.or(just("none").map(|_| Self::None))
 		.or(just("true")
 			.map(|_| true)
 			.or(just("false").map(|_| false))
diff --git a/src/lib.rs b/src/lib.rs
index d762348..995aba6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -53,6 +53,19 @@ impl Context {
 		Ok((parsed, value))
 	}
 
+	pub fn define(&mut self, name: impl ToString, value: Value) {
+		self.scope().borrow_mut().define(name.to_string(), value)
+	}
+
+	pub fn define_built(&mut self, name: impl ToString, op: impl Fn(Vec<Value>, &mut Context) -> FunRes + 'static) {
+		let def = FunImpl::Built(Rc::new(op) as Rc<BuiltFun>);
+		let function = Function {
+			capturing: Rc::new(RefCell::new(Scope::new(None))),
+			def,
+		};
+		self.define(name.to_string(), Value::Function(Rc::new(RefCell::new(function))))
+	}
+
 	pub fn scope(&self) -> Rc<RefCell<Scope>> {
 		self.frame.clone()
 	}
@@ -88,7 +101,7 @@ impl Scope {
 		result
 	}
 
-	pub fn append(&mut self, name: String, value: Value) {
+	pub fn define(&mut self, name: String, value: Value) {
 		self.defs.insert(name, value);
 	}
 
@@ -209,7 +222,7 @@ impl Function {
 			FunImpl::Def(def) => Scope::alt(context, self.capturing.clone(), |context| {
 				let names = def.args.iter().cloned();
 				for (name, value) in names.zip(args.into_iter().chain(repeat(Value::None))) {
-					context.scope().borrow_mut().append(name, value);
+					context.scope().borrow_mut().define(name, value);
 				}
 				match def.body.eval(context) {
 					Err(err) => Err(err),