diff --git a/cl-ast/src/ast_impl.rs b/cl-ast/src/ast_impl.rs
index ca07eb8..2712f8e 100644
--- a/cl-ast/src/ast_impl.rs
+++ b/cl-ast/src/ast_impl.rs
@@ -166,9 +166,30 @@ mod display {
     }
     impl Display for Function {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { name, args, body, rety } = self;
+            let Self { name, sign: sign @ TyFn { args, rety }, bind, body } = self;
+            let types = match **args {
+                TyKind::Tuple(TyTuple { ref types }) => types.as_slice(),
+                TyKind::Empty => Default::default(),
+                _ => {
+                    write!(f, "Invalid function signature: {sign}")?;
+                    Default::default()
+                }
+            };
+
+            debug_assert_eq!(bind.len(), types.len());
             write!(f, "fn {name} ")?;
-            delimit(separate(args, ", "), INLINE_PARENS)(f)?;
+            delimit(
+                |f| {
+                    for (idx, (arg, ty)) in bind.iter().zip(types.iter()).enumerate() {
+                        if idx != 0 {
+                            f.write_str(", ")?;
+                        }
+                        write!(f, "{arg}: {ty}")?;
+                    }
+                    Ok(())
+                },
+                INLINE_PARENS,
+            )(f)?;
             if let Some(rety) = rety {
                 write!(f, " -> {rety}")?;
             }
@@ -180,8 +201,8 @@ mod display {
     }
     impl Display for Param {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let Self { mutability, name, ty } = self;
-            write!(f, "{mutability}{name}: {ty}")
+            let Self { mutability, name } = self;
+            write!(f, "{mutability}{name}")
         }
     }
     impl Display for Struct {
diff --git a/cl-ast/src/lib.rs b/cl-ast/src/lib.rs
index 3e3c671..22e24e9 100644
--- a/cl-ast/src/lib.rs
+++ b/cl-ast/src/lib.rs
@@ -135,9 +135,9 @@ pub enum ModuleKind {
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct Function {
     pub name: Identifier,
-    pub args: Vec<Param>,
+    pub sign: TyFn,
+    pub bind: Vec<Param>,
     pub body: Option<Block>,
-    pub rety: Option<Box<Ty>>,
 }
 
 /// A single parameter for a [Function]
@@ -145,7 +145,6 @@ pub struct Function {
 pub struct Param {
     pub mutability: Mutability,
     pub name: Identifier,
-    pub ty: Box<Ty>,
 }
 
 /// A user-defined product type
diff --git a/cl-interpret/src/lib.rs b/cl-interpret/src/lib.rs
index 70d6901..a8f0f85 100644
--- a/cl-interpret/src/lib.rs
+++ b/cl-interpret/src/lib.rs
@@ -324,7 +324,7 @@ pub mod function {
             name
         }
         fn call(&self, env: &mut Environment, args: &[ConValue]) -> IResult<ConValue> {
-            let FnDecl { name: Identifier(name), args: declargs, body, rety: _ } = &*self.decl;
+            let FnDecl { name: Identifier(name), bind: declargs, body, sign: _ } = &*self.decl;
             // Check arg mapping
             if args.len() != declargs.len() {
                 return Err(Error::ArgNumber { want: declargs.len(), got: args.len() });
@@ -334,7 +334,7 @@ pub mod function {
             };
             // TODO: completely refactor data storage
             let mut frame = env.frame("fn args");
-            for (Param { mutability: _, name: Identifier(name), ty: _ }, value) in
+            for (Param { mutability: _, name: Identifier(name) }, value) in
                 declargs.iter().zip(args)
             {
                 frame.insert(name, Some(value.clone()));
diff --git a/cl-parser/src/parser.rs b/cl-parser/src/parser.rs
index c69a0d9..add07d8 100644
--- a/cl-parser/src/parser.rs
+++ b/cl-parser/src/parser.rs
@@ -394,20 +394,19 @@ impl<'t> Parser<'t> {
         const PARSING: Parsing = Parsing::Function;
         self.match_type(TokenKind::Fn, PARSING)?;
 
+        let name = self.identifier()?;
+        let (bind, types) = delim(Self::parse_params, PARENS, PARSING)(self)?;
+        let sign = TyFn {
+            args: Box::new(match types.len() {
+                0 => TyKind::Empty,
+                _ => TyKind::Tuple(TyTuple { types }),
+            }),
+            rety: self.parse_rety()?.map(Box::new),
+        };
         Ok(Function {
-            name: self.identifier()?,
-            args: self.parse_params()?,
-            rety: match self.peek_kind(PARSING)? {
-                TokenKind::Punct(Punct::LCurly) | TokenKind::Punct(Punct::Semi) => None,
-                TokenKind::Punct(Punct::Arrow) => {
-                    self.consume_peeked();
-                    Some(self.ty()?.into())
-                }
-                got => Err(self.error(
-                    ExpectedToken { want: TokenKind::Punct(Punct::Arrow), got },
-                    PARSING,
-                ))?,
-            },
+            name,
+            sign,
+            bind,
             body: match self.peek_kind(PARSING)? {
                 TokenKind::Punct(Punct::LCurly) => Some(self.block()?),
                 TokenKind::Punct(Punct::Semi) => {
@@ -420,25 +419,29 @@ impl<'t> Parser<'t> {
     }
 
     /// Parses the [parameters](Param) associated with a Function
-    pub fn parse_params(&mut self) -> PResult<Vec<Param>> {
+    pub fn parse_params(&mut self) -> PResult<(Vec<Param>, Vec<TyKind>)> {
         const PARSING: Parsing = Parsing::Function;
-        delim(
-            sep(Self::parse_param, Punct::Comma, PARENS.1, PARSING),
-            PARENS,
-            PARSING,
-        )(self)
+        let (mut params, mut types) = (vec![], vec![]);
+        while Ok(TokenKind::Punct(Punct::RParen)) != self.peek_kind(PARSING) {
+            let (param, ty) = self.parse_param()?;
+            params.push(param);
+            types.push(ty);
+            if self.match_op(Punct::Comma, PARSING).is_err() {
+                break;
+            }
+        }
+        Ok((params, types))
     }
 
     /// Parses a single function [parameter](Param)
-    pub fn parse_param(&mut self) -> PResult<Param> {
-        Ok(Param {
-            mutability: self.mutability()?,
-            name: self.identifier()?,
-            ty: {
+    pub fn parse_param(&mut self) -> PResult<(Param, TyKind)> {
+        Ok((
+            Param { mutability: self.mutability()?, name: self.identifier()? },
+            {
                 self.match_op(Punct::Colon, Parsing::Param)?;
-                self.ty()?.into()
+                self.tykind()?
             },
-        })
+        ))
     }
 
     /// Parses a [`struct` definition](Struct)
@@ -680,13 +683,14 @@ impl<'t> Parser<'t> {
                 t if t.is_empty() => TyKind::Empty,
                 types => TyKind::Tuple(TyTuple { types }),
             }),
-            rety: match self.peek_kind(PARSING) {
-                Ok(TokenKind::Punct(Punct::Arrow)) => {
-                    self.consume_peeked();
-                    Some(self.ty()?.into())
-                }
-                _ => None,
-            },
+            rety: self.parse_rety()?.map(Into::into),
+        })
+    }
+
+    pub fn parse_rety(&mut self) -> PResult<Option<Ty>> {
+        Ok(match self.match_op(Punct::Arrow, Parsing::TyFn) {
+            Ok(_) => Some(self.ty()?),
+            Err(_) => None,
         })
     }
 
diff --git a/cl-repl/examples/yaml.rs b/cl-repl/examples/yaml.rs
index 4d25979..ae82e30 100644
--- a/cl-repl/examples/yaml.rs
+++ b/cl-repl/examples/yaml.rs
@@ -247,12 +247,12 @@ pub mod yamlify {
     }
     impl Yamlify for Function {
         fn yaml(&self, y: &mut Yamler) {
-            let Self { name, args, body, rety } = self;
+            let Self { name, sign, bind, body } = self;
             y.key("Function")
                 .pair("name", name)
-                .pair("args", args)
-                .pair("body", body)
-                .pair("rety", rety);
+                .pair("sign", sign)
+                .pair("bind", bind)
+                .pair("body", body);
         }
     }
     impl Yamlify for Struct {
@@ -533,11 +533,8 @@ pub mod yamlify {
     }
     impl Yamlify for Param {
         fn yaml(&self, y: &mut Yamler) {
-            let Self { mutability, name, ty } = self;
-            y.key("Param")
-                .yaml(mutability)
-                .pair("name", name)
-                .pair("ty", ty);
+            let Self { mutability, name } = self;
+            y.key("Param").yaml(mutability).pair("name", name);
         }
     }
     impl Yamlify for Ty {