diff --git a/src/interpreter/context.rs b/src/interpreter/context.rs
index d073b2e..ee75b08 100644
--- a/src/interpreter/context.rs
+++ b/src/interpreter/context.rs
@@ -28,6 +28,16 @@ impl<'s> Context<'s> {
         }
     }
 
+    /// Execute whole function and return last value on stack (or nil)
+    pub fn execute(&mut self) -> Result<Value<'s>> {
+        let len = self.fun.bytecode.len();
+        while self.pc < len {
+            self.tick()?;
+        }
+
+        Ok(self.stack.pop().unwrap_or(Value::Nil))
+    }
+
     /// Execute next instruction
     pub fn tick(&mut self) -> Result<()> {
         use Instruction::*;
@@ -41,10 +51,25 @@ impl<'s> Context<'s> {
             Call(n) if n >= self.stack.len() => return Err(IndexOutOfBoundsError::Stack.into()),
             Call(n) => {
                 let fun = self.stack_pop()?;
+                let mut args = self.stack.split_off(self.stack.len() - n);
                 match fun {
-                    Value::Function(_) => todo!("function calls"),
+                    Value::Function(fun) => {
+                        if fun.locals_len > args.len() {
+                            args.resize(fun.locals_len, Value::Nil);
+                        }
+
+                        self.stack.push(
+                            Context {
+                                stack: vec![],
+                                locals: args,
+                                pc: 0,
+                                fun,
+                            }
+                            .execute()?,
+                        );
+                    }
                     Value::NativeFun(NativeFun(f)) => {
-                        let v = f(&self.stack.split_off(self.stack.len() - n));
+                        let v = f(&args);
                         self.stack.push(v);
                     }
                     _ => unimplemented!("invalid function type"),