diff --git a/doc/examples/clockdiv.fut b/doc/examples/clockdiv.fut
index 7601376..40370a5 100644
--- a/doc/examples/clockdiv.fut
+++ b/doc/examples/clockdiv.fut
@@ -1,4 +1,4 @@
-module clockdiv_2 (
+proc clockdiv_2 (
 	clk: Logic,
 	rst: Logic
 ) -> Logic
diff --git a/doc/examples/comparator.fut b/doc/examples/comparator.fut
index 11a205b..2044af5 100644
--- a/doc/examples/comparator.fut
+++ b/doc/examples/comparator.fut
@@ -1,7 +1,7 @@
-module comparator (
+comb comparator (
 	a: Logic<8>,
 	b: Logic<8>
 ) -> Logic
 {
-	assign eq = ~reduce_or(a ^ b);
+	~reduce_or(a ^ b)
 }
diff --git a/doc/examples/halfadd.fut b/doc/examples/halfadd.fut
index e633ea8..de25d94 100644
--- a/doc/examples/halfadd.fut
+++ b/doc/examples/halfadd.fut
@@ -1,8 +1,12 @@
-module halfadd (
+struct Add {
+	sum: Logic,
+	carry: Logic
+}
+
+comb halfadd (
 	a: Logic,
 	b: Logic
-) -> (Logic, Logic)
+) -> Add
 {
-	assign sum = a ^ b;
-	assign carry = a & b;
+	Add{sum: a ^ b, carry: a & b}
 }
diff --git a/lib/builtins/main.hyd b/lib/builtins/main.hyd
index 3b23c26..fc1b56b 100644
--- a/lib/builtins/main.hyd
+++ b/lib/builtins/main.hyd
@@ -1,6 +1,6 @@
 
 
-module reduce_or (
+comb reduce_or (
 	a: Logic
 	)
 	-> Logic<1> {
diff --git a/src/frontend.rs b/src/frontend.rs
index ad1ec7d..2346c2e 100644
--- a/src/frontend.rs
+++ b/src/frontend.rs
@@ -2,6 +2,7 @@ use std::collections::BTreeMap;
 
 use crate::builtin_cells::get_builtins;
 use crate::parser;
+use crate::parser::expression::Expression;
 use crate::rtlil;
 use crate::rtlil::RtlilWrite;
 pub use callable::Callable;
@@ -169,70 +170,59 @@ fn lower_process(
     Ok(())
 }
 
-fn desugar_operation<'a>(op: parser::Operation<'a>) -> parser::Call<'a> {
-    match op {
-        parser::Operation::And { a, b } => {
-            let a = desugar_expression(a);
-            let b = desugar_expression(b);
-            parser::Call {
-                name: "and".into(),
-                args: vec![a, b],
-            }
-        }
-        parser::Operation::Or { a, b } => {
-            let a = desugar_expression(a);
-            let b = desugar_expression(b);
-            parser::Call {
-                name: "or".into(),
-                args: vec![a, b],
-            }
-        }
-        parser::Operation::Xor { a, b } => {
-            let a = desugar_expression(a);
-            let b = desugar_expression(b);
-            parser::Call {
-                name: "xor".into(),
-                args: vec![a, b],
-            }
-        }
-        parser::Operation::Not(a) => {
-            let a = desugar_expression(a);
-            parser::Call {
-                name: "not".into(),
-                args: vec![a],
-            }
-        }
+fn desugar_binop<'a>(op: parser::expression::BinOp<'a>) -> parser::expression::Call<'a> {
+    let a = desugar_expression(op.a);
+    let b = desugar_expression(op.b);
+    let op_func = match op.kind {
+        parser::expression::BinOpKind::And => "and",
+        parser::expression::BinOpKind::Or => "or",
+        parser::expression::BinOpKind::Xor => "xor",
+    };
+    parser::expression::Call {
+        name: op_func.into(),
+        args: vec![a, b],
     }
 }
 
-fn desugar_expression<'a>(expr: parser::Expression<'a>) -> parser::Expression<'a> {
+fn desugar_unop<'a>(op: parser::expression::UnOp<'a>) -> parser::expression::Call<'a> {
+    let a = desugar_expression(op.a);
+    let op_func = match op.kind {
+        parser::expression::UnOpKind::BitNot => "not",
+        parser::expression::UnOpKind::Not => todo!(),
+    };
+    parser::expression::Call {
+        name: op_func.into(),
+        args: vec![a],
+    }
+}
+
+fn desugar_expression<'a>(expr: Expression<'a>) -> Expression<'a> {
     // TODO: allow ergonomic traversal of AST
     match expr {
-        parser::Expression::Ident(_) => expr,
-        parser::Expression::Literal(_) => expr,
-        parser::Expression::Call(mut call) => {
+        Expression::Path(_) => expr,
+        Expression::Literal(_) => expr,
+        Expression::Call(mut call) => {
             let new_args = call.args.into_iter().map(desugar_expression).collect();
             call.args = new_args;
-            parser::Expression::Call(call)
-        }
-        parser::Expression::Operation(op) => {
-            parser::Expression::Call(Box::new(desugar_operation(*op)))
+            Expression::Call(call)
         }
+        Expression::BinOp(op) => Expression::Call(Box::new(desugar_binop(*op))),
+        Expression::UnOp(op) => Expression::Call(Box::new(desugar_unop(*op))),
     }
 }
 
 fn lower_expression(
     ctx: &Context,
     module: &mut rtlil::Module,
-    expr: &parser::Expression,
+    expr: &Expression,
 ) -> Result<rtlil::SigSpec, CompileError> {
     let expr = desugar_expression(expr.clone());
     match expr {
-        parser::Expression::Ident(ident) => {
+        Expression::Path(ident) => {
             let signal = ctx.try_get_signal(ident)?;
             Ok(signal.sigspec())
         }
-        parser::Expression::Call(call) => {
+        Expression::Call(call) => {
             let args_resolved = call
                 .args
                 .iter()
@@ -268,8 +258,12 @@ fn lower_expression(
         }
         // TODO: instantiate operators directly here instead of desugaring, once the callable infrastructure improves
         // to get better errors
-        parser::Expression::Operation(_op) => todo!("operators not yet implemented"),
-        parser::Expression::Literal(lit) => Ok(rtlil::SigSpec::Const(lit as i64, TODO_WIDTH)),
+        Expression::Literal(lit) => Ok(rtlil::SigSpec::Const(
+            lit.span().fragment().parse().unwrap(),
+            TODO_WIDTH,
+        )),
+        Expression::UnOp(_) => todo!(),
+        Expression::BinOp(_) => todo!(),
     }
 }
 
@@ -284,6 +278,39 @@ fn lower_assignment(
     Ok(())
 }
 
+fn lower_comb(
+    ctx: &mut Context,
+    module: &mut rtlil::Module,
+    pa_comb: parser::comb::CombBlock,
+) -> Result<(), CompileError> {
+    for (num, port) in pa_comb.ports.iter().enumerate() {
+        let port_id = make_pubid(port.net.name.fragment());
+        module.add_wire(rtlil::Wire::new(
+            port_id.clone(),
+            TODO_WIDTH,
+            Some(rtlil::PortOption::Input((num + 1) as i32)),
+        ));
+        let typ = TypeStruct::logic_width(TODO_WIDTH);
+        let signal = Signal {
+            name: port.net.name.fragment().to_string(),
+            il_id: port_id,
+            // TODO: CRIMES CRIMES CRIMES
+            typ: Box::leak(Box::new(typ)),
+        };
+        ctx.signals
+            .insert(port.net.name.fragment().to_string(), signal);
+    }
+    let ret_id = module.make_genid("ret");
+    module.add_wire(rtlil::Wire::new(
+        ret_id.clone(),
+        TODO_WIDTH,
+        Some(rtlil::PortOption::Input(99)),
+    ));
+    let out_sig = lower_expression(ctx, module, &pa_comb.expr)?;
+    module.add_connection(&rtlil::SigSpec::Wire(ret_id), &out_sig);
+    Ok(())
+}
+
 pub fn lower_module(pa_module: parser::Module) -> Result<String, CompileError> {
     let mut writer = rtlil::ILWriter::new();
     let mut ir_module = rtlil::Module::new(make_pubid("test"));
@@ -297,38 +324,13 @@ pub fn lower_module(pa_module: parser::Module) -> Result<String, CompileError> {
     };
 
     writer.write_line("autoidx 1");
-    /*
-    for (idx, port) in pa_module.ports.iter().enumerate() {
-        // FIXME: Actually resolve types
-        let sigtype = TypeStruct::logic_width(TODO_WIDTH);
-        // FIXME: CRIMES CRIMES CRIMES
-        let sigtype = Box::leak(Box::new(sigtype));
-        let sig = Signal {
-            name: port.net.name.fragment().to_string(),
-            il_id: make_pubid(port.net.name.fragment()),
-            typ: sigtype,
-        };
-        let sig = context
-            .signals
-            .entry(port.net.name.fragment().to_string())
-            .or_insert(sig);
-
-        let dir_option = match port.direction {
-            parser::PortDirection::Input => rtlil::PortOption::Input(idx as i32 + 1),
-            parser::PortDirection::Output => rtlil::PortOption::Output(idx as i32 + 1),
-        };
-        let wire = rtlil::Wire::new(sig.il_id.to_owned(), TODO_WIDTH, Some(dir_option));
-        ir_module.add_wire(wire);
-    }
     for item in pa_module.items {
         match item {
-            parser::ModuleItem::Assign(assignment) => {
-                lower_assignment(&context, &mut ir_module, assignment)?
-            }
-            parser::ModuleItem::Proc(proc) => lower_process(&context, &mut ir_module, &proc)?,
+            parser::ModuleItem::Comb(comb) => lower_comb(&mut context, &mut ir_module, comb)?,
+            parser::ModuleItem::Proc(_) => todo!(),
+            parser::ModuleItem::State(_) => todo!(),
         }
     }
     ir_module.write_rtlil(&mut writer);
-    */
     Ok(writer.finish())
 }
diff --git a/src/parser/comb.rs b/src/parser/comb.rs
index 5d06dae..2cdb6da 100644
--- a/src/parser/comb.rs
+++ b/src/parser/comb.rs
@@ -1,4 +1,6 @@
 use super::{
+    declaration::TypeName,
+    expression::{expression, Expression},
     module::inputs_list,
     module::PortDecl,
     tokens::{token, TokenKind as tk, TokenSpan},
@@ -16,6 +18,8 @@ use nom::{
 pub struct CombBlock<'a> {
     pub name: Span<'a>,
     pub ports: Vec<PortDecl<'a>>,
+    pub ret: TypeName<'a>,
+    pub expr: Expression<'a>,
 }
 
 pub fn comb_block(input: TokenSpan) -> IResult<TokenSpan, CombBlock> {
@@ -26,17 +30,15 @@ pub fn comb_block(input: TokenSpan) -> IResult<TokenSpan, CombBlock> {
                 token(tk::Ident),
                 delimited(token(tk::LParen), inputs_list, token(tk::RParen)),
                 preceded(token(tk::RArrow), typename),
-                delimited(
-                    token(tk::LBrace),
-                    many0(token(tk::Error)),
-                    token(tk::RBrace),
-                ),
+                delimited(token(tk::LBrace), expression, token(tk::RBrace)),
             ))),
         ),
-        |(name, inputs, _ret, _items)| CombBlock {
+        |(name, inputs, ret, expr)| CombBlock {
             // TODO: bring back returns
             name: name.span(),
             ports: inputs,
+            ret,
+            expr,
         },
     )(input)
 }
diff --git a/src/parser/expression.rs b/src/parser/expression.rs
index 14de774..f64939a 100644
--- a/src/parser/expression.rs
+++ b/src/parser/expression.rs
@@ -1,4 +1,4 @@
-use super::tokens::{token, TokenKind as tk, TokenSpan};
+use super::tokens::{token, Token, TokenKind as tk, TokenSpan};
 use super::{IResult, Span};
 use nom::{
     branch::alt,
@@ -7,48 +7,95 @@ use nom::{
     sequence::{delimited, preceded, separated_pair, tuple},
 };
 
-#[derive(Debug, Clone)]
-pub enum Operation<'a> {
-    And {
-        a: Expression<'a>,
-        b: Expression<'a>,
-    },
-    Or {
-        a: Expression<'a>,
-        b: Expression<'a>,
-    },
-    Xor {
-        a: Expression<'a>,
-        b: Expression<'a>,
-    },
-    Not(Expression<'a>),
-}
-
-pub fn operation(input: TokenSpan) -> IResult<TokenSpan, Operation> {
-    // temporarily given up on before I learn the shunting yard algorithm
-    alt((
-        map(
-            separated_pair(expression_nonrecurse, token(tk::BitAnd), expression),
-            |(a, b)| Operation::And { a, b },
-        ),
-        map(
-            separated_pair(expression_nonrecurse, token(tk::BitOr), expression),
-            |(a, b)| Operation::Or { a, b },
-        ),
-        map(
-            separated_pair(expression_nonrecurse, token(tk::BitXor), expression),
-            |(a, b)| Operation::Xor { a, b },
-        ),
-        map(preceded(token(tk::BitNot), expression), Operation::Not),
-    ))(input)
-}
-
 #[derive(Debug, Clone)]
 pub struct Call<'a> {
     pub name: Span<'a>,
     pub args: Vec<Expression<'a>>,
 }
 
+#[derive(Debug, Clone)]
+pub enum BinOpKind {
+    And,
+    Or,
+    Xor,
+}
+
+#[derive(Debug, Clone)]
+pub enum UnOpKind {
+    Not,
+    BitNot,
+}
+
+#[derive(Debug, Clone)]
+pub struct BinOp<'a> {
+    pub a: Expression<'a>,
+    pub b: Expression<'a>,
+    pub kind: BinOpKind,
+}
+
+#[derive(Debug, Clone)]
+pub struct UnOp<'a> {
+    pub a: Expression<'a>,
+    pub kind: UnOpKind,
+}
+
+#[derive(Debug, Clone)]
+pub enum Expression<'a> {
+    Path(&'a str),
+    Literal(Token<'a>),
+    UnOp(Box<UnOp<'a>>),
+    BinOp(Box<BinOp<'a>>),
+    Call(Box<Call<'a>>),
+}
+
+/// expressions that can't be subdivided further
+fn atom(input: TokenSpan) -> IResult<TokenSpan, Expression> {
+    alt((
+        map(call_item, |call| Expression::Call(Box::new(call))),
+        map(token(tk::Ident), |it| {
+            Expression::Path(it.span().fragment())
+        }),
+        map(token(tk::Number), Expression::Literal),
+        delimited(token(tk::LParen), expression, token(tk::RParen)),
+    ))(input)
+}
+
+fn unop_kind(input: TokenSpan) -> IResult<TokenSpan, UnOpKind> {
+    alt((
+        map(token(tk::Not), |_| UnOpKind::Not),
+        map(token(tk::BitNot), |_| UnOpKind::BitNot),
+    ))(input)
+}
+
+/// unary expressions e.g `~expr`, `!expr`
+fn unary(input: TokenSpan) -> IResult<TokenSpan, Expression> {
+    alt((
+        map(tuple((unop_kind, unary)), |(kind, expr)| {
+            Expression::UnOp(Box::new(UnOp { a: expr, kind }))
+        }),
+        atom,
+    ))(input)
+}
+
+fn bitop_kind(input: TokenSpan) -> IResult<TokenSpan, BinOpKind> {
+    alt((
+        map(token(tk::BitXor), |_| BinOpKind::Xor),
+        map(token(tk::BitOr), |_| BinOpKind::Xor),
+        map(token(tk::BitAnd), |_| BinOpKind::Xor),
+    ))(input)
+}
+
+/// bit and, or, xor e.g. a ^ b & c
+/// TODO: make precedence rules for bit ops
+fn bitop(input: TokenSpan) -> IResult<TokenSpan, Expression> {
+    alt((
+        map(tuple((unary, bitop_kind, bitop)), |(a, kind, b)| {
+            Expression::BinOp(Box::new(BinOp { a, b, kind }))
+        }),
+        unary,
+    ))(input)
+}
+
 pub fn call_item(input: TokenSpan) -> IResult<TokenSpan, Call> {
     map(
         tuple((
@@ -66,32 +113,54 @@ pub fn call_item(input: TokenSpan) -> IResult<TokenSpan, Call> {
     )(input)
 }
 
-#[derive(Debug, Clone)]
-pub enum Expression<'a> {
-    Ident(&'a str),
-    Literal(u64),
-    Call(Box<Call<'a>>),
-    Operation(Box<Operation<'a>>),
-}
-
 /// parser combinators can not parse left-recursive grammars. To work around this, we split
 /// expressions into a recursive and non-recursive portion.
 /// Parsers reachable from this point must call expression_nonrecurse instead
 pub fn expression(input: TokenSpan) -> IResult<TokenSpan, Expression> {
-    alt((
-        map(operation, |op| Expression::Operation(Box::new(op))),
-        expression_nonrecurse,
-    ))(input)
+    bitop(input)
 }
 
-/// the portion of the expression grammar that can be parsed without left recursion
-fn expression_nonrecurse(input: TokenSpan) -> IResult<TokenSpan, Expression> {
-    alt((
-        map(token(tk::Number), |_| Expression::Literal(42)),
-        map(call_item, |call| Expression::Call(Box::new(call))),
-        map(token(tk::Ident), |ident| {
-            Expression::Ident(*ident.span().fragment())
-        }),
-        delimited(token(tk::LParen), expression, token(tk::RParen)),
-    ))(input)
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::parser::tokens::{lex, Token, TokenSpan};
+    use crate::parser::Span;
+    use nom::combinator::all_consuming;
+
+    fn tok(input: &'static str) -> Vec<Token> {
+        let input = Span::from(input);
+        lex(input).unwrap().1
+    }
+
+    fn fullexpr(input: TokenSpan) -> IResult<TokenSpan, Expression> {
+        all_consuming(expression)(input)
+    }
+
+    #[test]
+    fn test_atoms() {
+        fullexpr(TokenSpan::new(&tok("a"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("(a)"))).unwrap();
+    }
+
+    #[test]
+    fn test_unary() {
+        fullexpr(TokenSpan::new(&tok("asdf"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("~(asdf)"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("!asdf"))).unwrap();
+        // unary(TokenSpan::new(&tok("~!(asdf)"))).unwrap();
+    }
+
+    #[test]
+    fn test_bitop() {
+        fullexpr(TokenSpan::new(&tok("a | b"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("a ^ b"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("~(a ^ b)"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("a ^ !b"))).unwrap();
+        fullexpr(TokenSpan::new(&tok("a & !b & c"))).unwrap();
+    }
+
+    #[test]
+    fn test_call() {
+        fullexpr(TokenSpan::new(&tok("a()"))).unwrap();
+    }
 }
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 79d8343..d1ece5f 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -20,7 +20,6 @@ pub type IResult<I, O, E = IErr<I>> = nom::IResult<I, O, E>;
 pub use crate::parser::declaration::{
     assign_statement, declaration, typename, Assign, NetDecl, TypeName,
 };
-pub use crate::parser::expression::{expression, Call, Expression, Operation};
 pub use crate::parser::module::{module, Module, ModuleItem, PortDirection};
 use crate::parser::tokens::TokenSpan;
 use nom::combinator::all_consuming;
diff --git a/src/parser/proc.rs b/src/parser/proc.rs
index 7f52de4..1008f09 100644
--- a/src/parser/proc.rs
+++ b/src/parser/proc.rs
@@ -8,8 +8,9 @@ use nom::{
 
 use crate::parser::{
     assign_statement, expression,
+    expression::{expression, Expression},
     tokens::{token, TokenKind as tk, TokenSpan},
-    Assign, Expression, IResult, Span,
+    Assign, IResult, Span,
 };
 
 #[derive(Debug)]
diff --git a/src/parser/tokens.rs b/src/parser/tokens.rs
index b496ec7..59734c1 100644
--- a/src/parser/tokens.rs
+++ b/src/parser/tokens.rs
@@ -70,6 +70,7 @@ pub enum TokenKind {
     BitOr,
     BitXor,
     EqAssign,
+    Not,
     // Multi Chars
     FatArrow,
     RArrow,
@@ -204,6 +205,7 @@ fn lex_punctuation(input: Span) -> IResult<Span, Token> {
             map(tag("&"), |_| TokenKind::BitAnd),
             map(tag("^"), |_| TokenKind::BitXor),
             map(tag("|"), |_| TokenKind::BitOr),
+            map(tag("!"), |_| TokenKind::Not),
             map(tag("="), |_| TokenKind::EqAssign),
         ))),
         |(span, kind)| Token::new(span, kind),