diff --git a/Cargo.toml b/Cargo.toml
index 992ec19..a11643b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-bumpalo = "3"
+bumpalo = { version = "3", features = ["collections"] }
 chumsky = "1.0.0-alpha"
 lasso   = "0.7"
 logos   = "0.13"
diff --git a/src/main.rs b/src/main.rs
index e073dd7..b4f78c5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -14,12 +14,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let lexer = syntax::token::Token::lexer_with_extras(&buf, default());
     let arena = Bump::new();
-    syntax::parser::parse(
-        lexer
-            .spanned()
-            .map(|(item, span)| (item.unwrap_or(syntax::token::Token::Invalid), span.into())),
-        &arena,
-    );
+    syntax::parser::parse_lexer(lexer, &arena);
 
     Ok(())
 }
diff --git a/src/syntax/ast.rs b/src/syntax/ast.rs
index 4e1fa1c..e351646 100644
--- a/src/syntax/ast.rs
+++ b/src/syntax/ast.rs
@@ -1,12 +1,47 @@
-use lasso::Spur;
+use {super::token::IntLit, chumsky::span::SimpleSpan, lasso::Spur};
 
-use super::token::IntLit;
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Spanned<T> {
+    pub item: T,
+    pub span: SimpleSpan,
+}
+
+impl<T> Spanned<T> {
+    #[inline]
+    pub fn new(item: T, span: SimpleSpan) -> Self {
+        Self { item, span }
+    }
+}
+
+pub type SpanExpr<'a> = Spanned<Expr<'a>>;
+pub type ExprRef<'a> = &'a SpanExpr<'a>;
+pub type ExprList<'a> = &'a [SpanExpr<'a>];
+pub type Ident = Spur;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Expr<'a> {
-    Binary(BinaryOperator, &'a Self, &'a Self),
-    Unary(UnaryOperator, &'a Self),
+    Ident(Ident),
+    Path(ExprList<'a>),
     Literal(Literal),
+    Call(ExprRef<'a>, ExprList<'a>),
+    Binary(Spanned<BinaryOperator>, ExprRef<'a>, ExprRef<'a>),
+    Unary(Spanned<UnaryOperator>, ExprRef<'a>),
+    BindLocal(ExprRef<'a>, Spanned<Pattern>, Option<ExprList<'a>>),
+    BindIn(
+        ExprRef<'a>,
+        Spanned<Pattern>,
+        ExprList<'a>,
+        Option<ExprList<'a>>,
+    ),
+    Match(ExprRef<'a>, &'a [(Spanned<Pattern>, SpanExpr<'a>)]),
+    Set(ExprRef<'a>, ExprRef<'a>),
+    Func(Ident, &'a [Spanned<Pattern>], ExprRef<'a>),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Pattern {
+    Ident(Ident),
+    None,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
diff --git a/src/syntax/parser.rs b/src/syntax/parser.rs
index 92adc53..5266491 100644
--- a/src/syntax/parser.rs
+++ b/src/syntax/parser.rs
@@ -1,18 +1,107 @@
-use super::{ast::Expr, token::Token};
-use bumpalo::Bump;
-use chumsky::{extra::Full, input::Stream, prelude::*};
+use super::ast::{Literal, SpanExpr};
 
-type Item = (Token, SimpleSpan);
-type Extra<'s> = Full<Rich<'s, Item, SimpleSpan>, State<'s>, ()>;
-struct State<'a> {
+use {
+    super::{
+        ast::{Expr, Spanned},
+        token::Token,
+    },
+    crate::utils::Pipe,
+    bumpalo::Bump,
+    chumsky::{
+        extra::Full,
+        input::{Stream, ValueInput},
+        prelude::*,
+    },
+    logos::Lexer,
+};
+
+fn expr<'a, I>() -> impl Parser<'a, I, SpanExpr<'a>, Extra<'a>> + Clone
+where
+    I: Input<'a, Token = Token, Span = SimpleSpan> + ValueInput<'a>,
+{
+    recursive(|expr| {
+        let ident = select!(Token::Ident(id) => Expr::Ident(id));
+        let atom = {
+            // Literal
+            select! {
+                Token::Int(a) => Literal::Integer(a),
+                Token::String(a) => Literal::String(a)
+            }
+            .map(Expr::Literal)
+        }
+        .or(ident)
+        .map_with_span(Spanned::new)
+        .or(expr
+            .clone()
+            .delimited_by(just(Token::LeftParen), just(Token::RightParen)));
+
+        let call = atom
+            .clone()
+            .pipe(arena_box)
+            .then(
+                expr.clone()
+                    .separated_by(just(Token::Comma))
+                    .allow_trailing()
+                    .pipe(arena_collect)
+                    .delimited_by(just(Token::LeftParen), just(Token::RightParen)),
+            )
+            .map(|(expr, params)| Expr::Call(expr, params));
+
+        call.map_with_span(Spanned::new).or(atom)
+    })
+}
+
+pub struct State<'a> {
+    pub arena: &'a Bump,
+}
+pub type Extra<'a> = Full<Rich<'a, Token>, State<'a>, ()>;
+
+pub fn parse_input<'a>(
+    input: impl ValueInput<'a, Token = Token, Span = SimpleSpan>,
     arena: &'a Bump,
+) {
+    println!("{:?}", expr().parse_with_state(input, &mut State { arena }));
 }
 
-pub fn parse(input: impl Iterator<Item = Item>, arena: &Bump) {
-    expr().parse_with_state(Stream::from_iter(input), &mut State { arena });
+pub fn parse_iter(
+    input: impl Iterator<Item = (Token, SimpleSpan)>,
+    eoi: impl Into<SimpleSpan>,
+    arena: &Bump,
+) {
+    parse_input(Stream::from_iter(input).spanned(eoi.into()), arena)
 }
 
-fn expr<'s, 'a, I: Iterator<Item = (Token, SimpleSpan)> + 's>(
-) -> impl Parser<'s, Stream<I>, Expr<'a>, Extra<'s>> {
-    todo()
+pub fn parse_lexer(input: Lexer<Token>, arena: &Bump) {
+    let end = input.span().end;
+    parse_iter(
+        input
+            .spanned()
+            .map(|(token, span)| (token.unwrap_or(Token::Invalid), span.into())),
+        end..end + 1,
+        arena,
+    )
+}
+
+fn arena_collect<'a, I, O: 'a>(
+    parser: impl IterParser<'a, I, O, Extra<'a>> + Clone,
+) -> impl Parser<'a, I, &'a [O], Extra<'a>> + Clone
+where
+    I: Input<'a, Span = SimpleSpan, Token = Token>,
+{
+    empty()
+        .map_with_state(|_, _, state: &mut State| bumpalo::vec![in state.arena])
+        .foldl(parser, |mut v, o| {
+            v.push(o);
+            v
+        })
+        .map(bumpalo::collections::Vec::into_bump_slice)
+}
+
+fn arena_box<'a, I, O: 'a>(
+    parser: impl Parser<'a, I, O, Extra<'a>> + Clone,
+) -> impl Parser<'a, I, &'a O, Extra<'a>> + Clone
+where
+    I: Input<'a, Span = SimpleSpan, Token = Token>,
+{
+    parser.map_with_state(|item, _, state| &*state.arena.alloc(item))
 }
diff --git a/src/utils.rs b/src/utils.rs
index 31a900e..6b4c784 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -2,3 +2,14 @@
 pub fn default<T: Default>() -> T {
     Default::default()
 }
+
+pub trait Pipe {
+    fn pipe<R>(self, mut f: impl FnMut(Self) -> R) -> R
+    where
+        Self: Sized,
+    {
+        f(self)
+    }
+}
+
+impl<T> Pipe for T {}