diff --git a/schala-lang/language/src/ast.rs b/schala-lang/language/src/ast.rs
index d440a82..0934c49 100644
--- a/schala-lang/language/src/ast.rs
+++ b/schala-lang/language/src/ast.rs
@@ -43,7 +43,13 @@ pub enum Statement {
 
 pub type Block = Vec<Meta<Statement>>;
 pub type ParamName = Rc<String>;
-pub type FormalParam = (ParamName, Option<TypeIdentifier>);
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct FormalParam {
+  pub name: ParamName,
+  pub default: Option<Expression>,
+  pub anno: Option<TypeIdentifier>
+}
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum Declaration {
diff --git a/schala-lang/language/src/parsing.rs b/schala-lang/language/src/parsing.rs
index 1706ef5..2c4d790 100644
--- a/schala-lang/language/src/parsing.rs
+++ b/schala-lang/language/src/parsing.rs
@@ -461,14 +461,16 @@ impl Parser {
     Ok(delimited!(self, LParen, formal_param, Comma, RParen))
   }
 
+  //TODO needs to support default values
   #[recursive_descent_method]
   fn formal_param(&mut self) -> ParseResult<FormalParam> {
     let name = self.identifier()?;
-    let ty = match self.token_handler.peek_kind() {
+    let anno = match self.token_handler.peek_kind() {
       Colon => Some(self.type_anno()?),
       _ => None
     };
-    Ok((name, ty))
+    let default = None;
+    Ok(FormalParam { name, anno, default })
   }
 
   #[recursive_descent_method]
@@ -1185,7 +1187,7 @@ mod parse_tests {
   use super::tokenize;
   use super::ParseResult;
   use crate::builtin::{PrefixOp, BinOp};
-  use crate::ast::{AST, Meta, Expression, Statement, IfExpressionBody, Discriminator, Pattern, PatternLiteral, TypeBody, Enumerator, ForBody, InvocationArgument};
+  use crate::ast::{AST, Meta, Expression, Statement, IfExpressionBody, Discriminator, Pattern, PatternLiteral, TypeBody, Enumerator, ForBody, InvocationArgument, FormalParam};
   use super::Statement::*;
   use super::Declaration::*;
   use super::Signature;
@@ -1375,15 +1377,16 @@ mod parse_tests {
 
     parse_test!("fn a(b, c: Int): Int", AST(vec![Meta::new(Declaration(
       FuncSig(Signature { name: rc!(a), operator: false, params: vec![
-        (rc!(b), None), (rc!(c), Some(ty!("Int")))
+        FormalParam { name: rc!(b), anno: None, default: None },
+        FormalParam { name: rc!(c), anno: Some(ty!("Int")), default: None }
       ], type_anno: Some(ty!("Int")) })))]));
 
 
     parse_test!("fn a(x) { x() }", AST(vec![Meta::new(Declaration(
-      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![(rc!(x),None)], type_anno: None },
+      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![FormalParam { name: rc!(x), anno: None, default: None }], type_anno: None },
         vec![exst!(Call { f: bx!(ex!(m val!("x"))), arguments: vec![] })])))]));
     parse_test!("fn a(x) {\n x() }", AST(vec![Meta::new(Declaration(
-      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![(rc!(x),None)], type_anno: None },
+      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![FormalParam { name: rc!(x), anno: None, default: None }], type_anno: None },
         vec![exst!(Call { f: bx!(ex!(m val!("x"))), arguments: vec![] })])))]));
 
     let multiline = r#"
@@ -1392,7 +1395,7 @@ fn a(x) {
 }
 "#;
     parse_test!(multiline, AST(vec![Meta::new(Declaration(
-      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![(rc!(x),None)], type_anno: None },
+      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![FormalParam { name: rc!(x), default: None, anno: None }], type_anno: None },
         vec![exst!(Call { f: bx!(ex!(m val!("x"))), arguments: vec![] })])))]));
     let multiline2 = r#"
 fn a(x) {
@@ -1402,7 +1405,7 @@ fn a(x) {
 }
 "#;
     parse_test!(multiline2, AST(vec![Meta::new(Declaration(
-      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![(rc!(x),None)], type_anno: None },
+      FuncDecl(Signature { name: rc!(a), operator: false, params: vec![FormalParam { name: rc!(x), default: None, anno: None }], type_anno: None },
         vec![exst!(s "x()")])))]));
   }
 
@@ -1535,7 +1538,14 @@ fn a(x) {
       Meta::new(Declaration(Interface {
         name: rc!(Unglueable),
         signatures: vec![
-          Signature { name: rc!(unglue), operator: false, params: vec![(rc!(a), Some(Singleton(TypeSingletonName { name: rc!(Glue), params: vec![] })))], type_anno: None },
+          Signature {
+            name: rc!(unglue),
+            operator: false,
+            params: vec![
+              FormalParam { name: rc!(a), anno: Some(Singleton(TypeSingletonName { name: rc!(Glue), params: vec![] })), default: None }
+            ],
+            type_anno: None
+          },
           Signature { name: rc!(mar), operator: false, params: vec![], type_anno: Some(Singleton(TypeSingletonName { name: rc!(Glue), params: vec![] })) },
         ]
       }))
@@ -1613,13 +1623,16 @@ fn a(x) {
   #[test]
   fn parsing_lambdas() {
     parse_test_wrap_ast! { r#"\(x) { x + 1}"#, exst!(
-        Lambda { params: vec![(rc!(x), None)], type_anno: None, body: vec![exst!(s "x + 1")] }
-      ) 
+        Lambda { params: vec![FormalParam { name: rc!(x), anno: None, default: None } ], type_anno: None, body: vec![exst!(s "x + 1")] }
+      )
     }
 
     parse_test!(r#"\  (x: Int, y) { a;b;c;}"#, AST(vec![
       exst!(Lambda {
-        params: vec![(rc!(x), Some(ty!("Int"))), (rc!(y), None)],
+        params: vec![
+          FormalParam { name: rc!(x), anno: Some(ty!("Int")), default: None },
+          FormalParam { name: rc!(y), anno: None, default: None }
+        ],
         type_anno: None,
         body: vec![exst!(s "a"), exst!(s "b"), exst!(s "c")]
       })
@@ -1627,8 +1640,10 @@ fn a(x) {
 
     parse_test!(r#"\(x){y}(1)"#, AST(vec![
       exst!(Call { f: bx!(ex!(m
-        Lambda { 
-          params: vec![(rc!(x), None)],
+        Lambda {
+          params: vec![
+            FormalParam { name: rc!(x), anno: None, default: None }
+          ],
           type_anno: None,
           body: vec![exst!(s "y")] }
         )),
@@ -1637,7 +1652,9 @@ fn a(x) {
     parse_test_wrap_ast! {
       r#"\(x: Int): String { "q" }"#,
       exst!(Lambda {
-        params: vec![(rc!(x), Some(ty!("Int")))],
+        params: vec![
+          FormalParam { name: rc!(x), anno: Some(ty!("Int")), default: None },
+        ],
         type_anno: Some(ty!("String")),
         body: vec![exst!(s r#""q""#)]
       })
@@ -1647,18 +1664,18 @@ fn a(x) {
   #[test]
   fn single_param_lambda() {
     parse_test_wrap_ast! {
-      r"\x { x + 10 }", 
+      r"\x { x + 10 }",
       exst!(Lambda {
-        params: vec![(rc!(x), None)],
+        params: vec![FormalParam { name: rc!(x), anno: None, default: None }],
         type_anno: None,
         body: vec![exst!(s r"x + 10")]
       })
     }
 
     parse_test_wrap_ast! {
-      r"\x: Nat { x + 10 }", 
+      r"\x: Nat { x + 10 }",
       exst!(Lambda {
-        params: vec![(rc!(x), Some(ty!("Nat")))],
+        params: vec![FormalParam { name: rc!(x), anno: Some(ty!("Nat")), default: None }],
         type_anno: None,
         body: vec![exst!(s r"x + 10")]
       })
diff --git a/schala-lang/language/src/reduced_ast.rs b/schala-lang/language/src/reduced_ast.rs
index 4aff5be..03e8300 100644
--- a/schala-lang/language/src/reduced_ast.rs
+++ b/schala-lang/language/src/reduced_ast.rs
@@ -165,7 +165,7 @@ impl Expression {
 fn reduce_lambda(params: &Vec<FormalParam>, body: &Block, symbol_table: &SymbolTable) -> Expr {
   Expr::Func(Func::UserDefined {
     name: None,
-    params: params.iter().map(|param| param.0.clone()).collect(),
+    params: params.iter().map(|param| param.name.clone()).collect(),
     body: reduce_block(body, symbol_table),
   })
 }
@@ -377,7 +377,7 @@ impl Declaration {
         name: name.clone(),
         func: Func::UserDefined {
           name: Some(name.clone()),
-          params: params.iter().map(|param| param.0.clone()).collect(),
+          params: params.iter().map(|param| param.name.clone()).collect(),
           body: reduce_block(&statements, symbol_table),
         }
       },
diff --git a/schala-lang/language/src/symbol_table.rs b/schala-lang/language/src/symbol_table.rs
index 1c0e28b..b06edf0 100644
--- a/schala-lang/language/src/symbol_table.rs
+++ b/schala-lang/language/src/symbol_table.rs
@@ -169,9 +169,9 @@ impl SymbolTable {
 
   fn add_function_signature(&mut self, signature: &Signature, scope_name_stack: &mut Vec<ScopeSegment>) -> Result<(), String> {
     let mut local_type_context = LocalTypeContext::new();
-    let types = signature.params.iter().map(|param| match param {
-      (_, Some(type_identifier)) => Rc::new(format!("{:?}", type_identifier)),
-      (_, None) => local_type_context.new_universal_type()
+    let types = signature.params.iter().map(|param| match param.anno {
+      Some(ref type_identifier) => Rc::new(format!("{:?}", type_identifier)),
+      None => local_type_context.new_universal_type()
     }).collect();
     self.add_new_symbol(&signature.name, scope_name_stack, SymbolSpec::Func(types));
     Ok(())
diff --git a/schala-lang/language/src/typechecking.rs b/schala-lang/language/src/typechecking.rs
index 3f1d595..43e81ec 100644
--- a/schala-lang/language/src/typechecking.rs
+++ b/schala-lang/language/src/typechecking.rs
@@ -369,7 +369,7 @@ impl<'a> TypeContext<'a> {
 
   fn lambda(&mut self, params: &Vec<FormalParam>, type_anno: &Option<TypeIdentifier>, _body: &Block) -> InferResult<Type> {
     let argument_types: InferResult<Vec<Type>> = params.iter().map(|param: &FormalParam| {
-      if let (_, Some(type_identifier)) = param {
+      if let FormalParam { anno: Some(type_identifier), ..  } = param {
         self.get_type_from_name(type_identifier)
       } else {
         Ok(Type::Var(self.fresh_type_variable()))