diff --git a/README.md b/README.md
index 0b46a6a..fce769a 100644
--- a/README.md
+++ b/README.md
@@ -130,8 +130,9 @@ fn get() -> [Customer] | Customer? | ():
 * test support
 
 ## What about performance?
-* Clueless really! We'll see.
-* But it is written in rust
+* Not optimizing for performance yet. First results look pretty bad.
+  * as in: purely recursive fibonacci of 38 (the 38th fibonacci number) takes 42 seconds on my machine (in release mode) :sad-face.
+* That said the idea is that a lot of processing is done within the virtual machine.
 * And it has no GC
 * So, maybe it will compete with python?
 
diff --git a/examples/fibonacci/fib.tp b/examples/fibonacci/fib.tp
index 92311a6..ae71050 100644
--- a/examples/fibonacci/fib.tp
+++ b/examples/fibonacci/fib.tp
@@ -4,4 +4,4 @@ fn fib(n: u64):
     else:
         fib(n-1) + fib(n-2)
 
-println(fib(10))
\ No newline at end of file
+println("fib = " + fib(38))
\ No newline at end of file
diff --git a/source/hello/web.tp b/source/hello/web.tp
index ecea46d..12b2f69 100644
--- a/source/hello/web.tp
+++ b/source/hello/web.tp
@@ -2,4 +2,4 @@ object Person:
     name: string
 
 fn get(path: string) -> string:
-    "hello" + path
\ No newline at end of file
+    "hello " + path
\ No newline at end of file
diff --git a/src/builtins/list.rs b/src/builtins/list.rs
index 42f4a93..af4f34a 100644
--- a/src/builtins/list.rs
+++ b/src/builtins/list.rs
@@ -22,6 +22,11 @@ pub(crate) fn list_functions() -> FunctionMap {
         "remove",
         Signature::new(vec![Parameter::new("index", U64)], U64, remove),
     );
+    add(
+        functions,
+        "sort",
+        Signature::new(vec![], U64, sort),
+    );
     list_functions
 }
 
@@ -55,6 +60,19 @@ fn len(self_val: RefMut<Value>, _args: Vec<Value>) -> Result<Value, RuntimeError
     }
 }
 
+fn sort(mut self_val: RefMut<Value>, _args: Vec<Value>) -> Result<Value, RuntimeError> {
+    if let Value::List(list) = self_val.deref_mut() {
+        if list.windows(2).any(|w| w[0].sort_cmp(&w[1]).is_none()) {
+            return Err(RuntimeError::NotSortable);
+        }
+
+        list.sort_by(|a, b| a.sort_cmp(b).unwrap());
+        Ok(Value::Void)
+    } else {
+        Err(expected_a_list())
+    }
+}
+
 fn expected_a_list() -> RuntimeError {
     expected("list")
 }
diff --git a/src/builtins/map.rs b/src/builtins/map.rs
new file mode 100644
index 0000000..0df972f
--- /dev/null
+++ b/src/builtins/map.rs
@@ -0,0 +1,64 @@
+use crate::builtins::{FunctionMap, Signature, add, expected};
+use crate::compiler::ast_pass::Parameter;
+use crate::compiler::tokens::TokenType;
+use crate::compiler::tokens::TokenType::{U64, Void};
+use crate::errors::RuntimeError;
+use crate::value::{Value, u64};
+use std::cell::RefMut;
+use std::collections::HashMap;
+use std::ops::{Deref, DerefMut};
+
+pub(crate) fn map_functions() -> FunctionMap {
+    let mut map_functions: FunctionMap = HashMap::new();
+    let functions = &mut map_functions;
+    add(functions, "len", Signature::new(vec![], U64, len));
+    add(
+        functions,
+        "insert",
+        Signature::new(
+            vec![
+                Parameter::new("key", TokenType::Any),
+                Parameter::new("value", TokenType::Any),
+            ],
+            Void,
+            insert,
+        ),
+    );
+    add(
+        functions,
+        "remove",
+        Signature::new(vec![Parameter::new("key", TokenType::Any)], Void, remove),
+    );
+    map_functions
+}
+
+fn remove(mut self_val: RefMut<Value>, mut args: Vec<Value>) -> Result<Value, RuntimeError> {
+    if let Value::Map(map) = self_val.deref_mut() {
+        let key = args.remove(0);
+        map.remove(&key);
+        Ok(Value::Void)
+    } else {
+        Err(expected_a_map())
+    }
+}
+
+fn insert(mut self_val: RefMut<Value>, mut args: Vec<Value>) -> Result<Value, RuntimeError> {
+    if let Value::Map(map) = self_val.deref_mut() {
+        map.insert(args.remove(0),args.remove(0));
+        Ok(Value::Void)
+    } else {
+        Err(expected_a_map())
+    }
+}
+
+fn len(self_val: RefMut<Value>, _args: Vec<Value>) -> Result<Value, RuntimeError> {
+    if let Value::Map(map) = self_val.deref() {
+        Ok(u64(map.len() as u64))
+    } else {
+        Err(expected_a_map())
+    }
+}
+
+fn expected_a_map() -> RuntimeError {
+    expected("map")
+}
diff --git a/src/builtins/mod.rs b/src/builtins/mod.rs
index f82a76d..c98c450 100644
--- a/src/builtins/mod.rs
+++ b/src/builtins/mod.rs
@@ -1,6 +1,7 @@
 mod string;
 mod list;
 pub(crate) mod globals;
+mod map;
 
 use std::cell::{RefCell, RefMut};
 use crate::builtins::string::string_functions;
@@ -12,6 +13,7 @@ use std::rc::Rc;
 use std::sync::LazyLock;
 use crate::compiler::ast_pass::Parameter;
 use crate::builtins::list::list_functions;
+use crate::builtins::map::map_functions;
 
 pub(crate) struct Signature {
     pub(crate) parameters: Vec<Parameter>,
@@ -32,8 +34,8 @@ impl Signature {
         }
     }
 
-    pub(crate) fn arity(&self) -> usize {
-        self.parameters.len()
+    pub(crate) fn arity(&self) -> u8 {
+        self.parameters.len() as u8
     }
 }
 
@@ -47,6 +49,7 @@ static FUNCTIONS: LazyLock<FunctionTable> = LazyLock::new(|| {
     let mut table: FunctionTable = HashMap::new();
     table.insert("string".to_string(), string_functions());
     table.insert("list".to_string(), list_functions());
+    table.insert("map".to_string(), map_functions());
 
     table
 });
diff --git a/src/compiler/assembly_pass.rs b/src/compiler/assembly_pass.rs
index 993ab19..b8dfb1b 100644
--- a/src/compiler/assembly_pass.rs
+++ b/src/compiler/assembly_pass.rs
@@ -270,7 +270,7 @@ impl AsmPass {
                             namespace, symbols, registry, arguments, parameters,
                         )?;
 
-                        self.emit(Call(name_index, arguments.len()));
+                        self.emit(Call(name_index, arguments.len() as u8));
                     }
                     // constructor function
                     Some(Symbol::Object { fields, .. }) => {
@@ -280,7 +280,7 @@ impl AsmPass {
                         self.get_arguments_in_order(
                             namespace, symbols, registry, arguments, fields,
                         )?;
-                        self.emit(Call(name_index, arguments.len()));
+                        self.emit(Call(name_index, arguments.len() as u8));
                     }
                     // maybe global function
                     _ => {
@@ -325,7 +325,7 @@ impl AsmPass {
                 });
                 let signature =
                     lookup(&receiver_type, method_name).map_err(|e| self.error_at_line(e))?;
-                if signature.arity() != arguments.len() {
+                if signature.arity() != arguments.len() as u8 {
                     return Err(self.error_at_line(CompilerError::IllegalArgumentsException(
                         format!("{}.{}", receiver_type, method_name),
                         signature.parameters.len(),
@@ -339,7 +339,7 @@ impl AsmPass {
                     arguments,
                     &signature.parameters,
                 )?;
-                self.emit(CallBuiltin(name_index, type_index, arguments.len()));
+                self.emit(CallBuiltin(name_index, type_index, arguments.len() as u8));
             }
             Expression::Variable { name, .. } => {
                 let name_index = self.vars.get(name);
@@ -444,11 +444,7 @@ impl AsmPass {
             }
             Expression::MapGet { .. } => {}
             Expression::FieldGet { .. } => {}
-            Expression::Range { lower, upper, .. } => {
-                // opposite order, because we have to assign last one first to the loop variable
-                // self.compile_expression(namespace, upper, symbols, registry)?;
-                // self.compile_expression(namespace, lower, symbols, registry)?;
-            }
+            Expression::Range { lower, .. } => {}
             Expression::ForStatement {
                 loop_var,
                 range,
@@ -550,7 +546,7 @@ pub enum Op {
     Divide,
     Negate,
     Return,
-    Call(usize, usize),
+    Call(usize, u8),
     And,
     Or,
     Not,
@@ -571,7 +567,7 @@ pub enum Op {
     DefMap(usize),
     Assign(usize),
     ListGet,
-    CallBuiltin(usize, usize, usize),
+    CallBuiltin(usize, usize, u8),
     Dup,
     GotoIf(usize),
     GotoIfNot(usize),
diff --git a/src/compiler/compiler_tests.rs b/src/compiler/compiler_tests.rs
index d4d9135..5a1fed6 100644
--- a/src/compiler/compiler_tests.rs
+++ b/src/compiler/compiler_tests.rs
@@ -4,9 +4,9 @@ mod tests {
     use crate::compiler::{compile, run};
     use crate::errors::CompilerError::{IllegalArgumentsException, ReservedFunctionName};
     use crate::errors::CompilerErrorAtLine;
-    use crate::errors::RuntimeError::{IllegalArgumentException, IndexOutOfBounds};
+    use crate::errors::RuntimeError::{IllegalArgumentException, IndexOutOfBounds, NotSortable};
     use crate::errors::TipiLangError::{Compiler, Runtime};
-    use crate::value::{Value, string};
+    use crate::value::{Value, string, i64};
     use chrono::DateTime;
 
     #[test]
@@ -299,6 +299,28 @@ date"#),
         assert_eq!(run(r#"[1,2,3].len()"#), Ok(Value::U64(3)));
     }
 
+    #[test]
+    fn list_sort() {
+        assert_eq!(
+            run(r#"
+let a = [3,2,1]
+a.sort()
+a"#),
+            Ok(Value::List(vec![i64(1), i64(2), i64(3)]))
+        );
+    }
+
+    #[test]
+    fn list_sort_invalid() {
+        assert_eq!(
+            run(r#"
+let a = [3,2,"a"]
+a.sort()
+a"#),
+            Err(Runtime(NotSortable))
+        );
+    }
+
     #[test]
     fn list_push() {
         assert_eq!(
@@ -449,7 +471,8 @@ let a:i64 = if true:
     42
 else:
     0
-a"#).unwrap();
+a"#)
+        .unwrap();
     }
     // #[test]
     // fn package() {
diff --git a/src/compiler/mod.rs b/src/compiler/mod.rs
index 4613571..9c9ec14 100644
--- a/src/compiler/mod.rs
+++ b/src/compiler/mod.rs
@@ -18,7 +18,7 @@ pub fn compile_sourcedir(source_dir: &str) -> Result<HashMap<String, AsmChunk>,
     for entry in WalkDir::new(source_dir).into_iter().filter_map(|e| e.ok()) {
         let path = entry.path().to_str().unwrap();
         if path.ends_with(TIPI_EXT) {
-            print!("-- Compiling {} -- ", path);
+            println!("-- Compiling {} -- ", path);
             let source = fs::read_to_string(path).map_err(map_underlying())?;
             let tokens = scan_pass::scan(&source)?;
             let mut symbol_table = HashMap::new();
diff --git a/src/errors.rs b/src/errors.rs
index 7d8f7b1..663d148 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -96,6 +96,8 @@ pub enum RuntimeError {
     ExpectedType(String),
     #[error("Index out of bounds: {0} > {1}")]
     IndexOutOfBounds(usize, usize),
+    #[error("The list contains values that are not comparable.")]
+    NotSortable,
 }
 
 #[derive(Error, Debug, PartialEq)]
diff --git a/src/lib.rs b/src/lib.rs
index ea2233c..3ef8583 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -11,7 +11,7 @@ pub mod file_watch;
 mod keywords;
 pub mod repl;
 mod symbol_builder;
-mod value;
+pub mod value;
 pub mod vm;
 
 pub(crate) type SymbolTable = HashMap<String, Symbol>;
diff --git a/src/value.rs b/src/value.rs
index 0fac67f..5d3919a 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -37,7 +37,7 @@ pub(crate) fn string(v: impl Into<String>) -> Value {
     Value::String(v.into())
 }
 
-pub(crate) fn _i64(v: impl Into<i64>) -> Value {
+pub(crate) fn i64(v: impl Into<i64>) -> Value {
     Value::I64(v.into())
 }
 
@@ -109,6 +109,24 @@ impl Value {
             _ => Err(ValueError::IllegalCast),
         }
     }
+
+    /// Comparison used for sorting lists.
+    /// Returns `None` when values are not comparable (different variants, unsupported types, etc.).
+    pub fn sort_cmp(&self, rhs: &Self) -> Option<Ordering> {
+        match (self, rhs) {
+            (Value::I32(a), Value::I32(b)) => Some(a.cmp(b)),
+            (Value::I64(a), Value::I64(b)) => Some(a.cmp(b)),
+            (Value::U32(a), Value::U32(b)) => Some(a.cmp(b)),
+            (Value::U64(a), Value::U64(b)) => Some(a.cmp(b)),
+            (Value::F32(a), Value::F32(b)) => Some(a.total_cmp(b)),
+            (Value::F64(a), Value::F64(b)) => Some(a.total_cmp(b)),
+            (Value::String(a), Value::String(b)) => Some(a.cmp(b)),
+            (Value::Char(a), Value::Char(b)) => Some(a.cmp(b)),
+            (Value::Bool(a), Value::Bool(b)) => Some(a.cmp(b)),
+            (Value::DateTime(a), Value::DateTime(b)) => Some(a.cmp(b)),
+            _ => None,
+        }
+    }
 }
 
 impl From<i32> for Value {