diff --git a/src/abstract_tree/function_call.rs b/src/abstract_tree/function_call.rs
index bb50c17..af16420 100644
--- a/src/abstract_tree/function_call.rs
+++ b/src/abstract_tree/function_call.rs
@@ -22,14 +22,34 @@ impl FunctionCall {
 
 impl AbstractTree for FunctionCall {
     fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        todo!()
+        if let Type::Function { return_type, .. } = self.function.expected_type(_context)? {
+            Ok(*return_type)
+        } else {
+            Err(ValidationError::ExpectedFunction)
+        }
     }
 
     fn validate(&self, _context: &Context) -> Result<(), ValidationError> {
-        todo!()
+        if let Type::Function { .. } = self.function.expected_type(_context)? {
+            Ok(())
+        } else {
+            Err(ValidationError::ExpectedFunction)
+        }
     }
 
     fn run(self, _context: &Context) -> Result<Action, RuntimeError> {
-        todo!()
+        let value = self.function.run(_context)?.as_value()?;
+        let function = value.as_function()?;
+        let mut arguments = Vec::with_capacity(self.arguments.len());
+
+        for expression in self.arguments {
+            let value = expression.run(_context)?.as_value()?;
+
+            arguments.push(value);
+        }
+
+        let function_context = Context::new();
+
+        function.call(arguments, function_context)
     }
 }
diff --git a/src/abstract_tree/mod.rs b/src/abstract_tree/mod.rs
index 20342af..7017019 100644
--- a/src/abstract_tree/mod.rs
+++ b/src/abstract_tree/mod.rs
@@ -48,6 +48,14 @@ pub enum Action {
 }
 
 impl Action {
+    pub fn as_value(self) -> Result<Value, ValidationError> {
+        match self {
+            Action::Break(value) => Ok(value),
+            Action::Return(value) => Ok(value),
+            Action::None => Err(ValidationError::ExpectedValue),
+        }
+    }
+
     pub fn as_return_value(self) -> Result<Value, ValidationError> {
         if let Action::Return(value) = self {
             Ok(value)
diff --git a/src/error.rs b/src/error.rs
index fd0cd20..b017cf3 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -88,6 +88,8 @@ impl Error {
                     ValidationError::CannotIndex(_) => todo!(),
                     ValidationError::CannotIndexWith(_, _) => todo!(),
                     ValidationError::InterpreterExpectedReturn => todo!(),
+                    ValidationError::ExpectedFunction => todo!(),
+                    ValidationError::ExpectedValue => todo!(),
                 }
 
                 report.finish()
@@ -143,7 +145,9 @@ pub enum ValidationError {
     CannotIndex(Type),
     CannotIndexWith(Type, Type),
     ExpectedBoolean,
+    ExpectedFunction,
     ExpectedIntegerOrFloat,
+    ExpectedValue,
     InterpreterExpectedReturn,
     RwLockPoison(RwLockPoisonError),
     TypeCheck(TypeCheckError),
diff --git a/src/value.rs b/src/value.rs
index 427e92c..ec11588 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -13,7 +13,7 @@ use stanza::{
 };
 
 use crate::{
-    abstract_tree::{Action, Identifier, Statement, Type},
+    abstract_tree::{AbstractTree, Action, Identifier, Statement, Type},
     context::Context,
     error::{RuntimeError, ValidationError},
 };
@@ -129,6 +129,14 @@ impl Value {
         Err(ValidationError::ExpectedBoolean)
     }
 
+    pub fn as_function(&self) -> Result<&Function, ValidationError> {
+        if let ValueInner::Function(function) = self.0.as_ref() {
+            return Ok(function);
+        }
+
+        Err(ValidationError::ExpectedFunction)
+    }
+
     pub fn as_list(&self) -> Option<&Vec<Value>> {
         if let ValueInner::List(list) = self.inner().as_ref() {
             Some(list)
@@ -338,6 +346,25 @@ pub enum Function {
     BuiltIn(BuiltInFunction),
 }
 
+impl Function {
+    pub fn call(&self, arguments: Vec<Value>, context: Context) -> Result<Action, RuntimeError> {
+        let action = match self {
+            Function::Parsed(ParsedFunction {
+                parameters, body, ..
+            }) => {
+                for ((identifier, _), value) in parameters.into_iter().zip(arguments.into_iter()) {
+                    context.set_value(identifier.clone(), value)?;
+                }
+
+                body.clone().run(&context)?
+            }
+            Function::BuiltIn(built_in_function) => built_in_function.call(arguments, &context)?,
+        };
+
+        Ok(action)
+    }
+}
+
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
 pub struct ParsedFunction {
     parameters: Vec<(Identifier, Type)>,
@@ -368,10 +395,10 @@ impl BuiltInFunction {
         }
     }
 
-    pub fn call(self, value: Value, _context: &Context) -> Result<Action, RuntimeError> {
+    pub fn call(&self, arguments: Vec<Value>, _context: &Context) -> Result<Action, RuntimeError> {
         match self {
             BuiltInFunction::Output => {
-                println!("{value}");
+                println!("{}", arguments[0]);
 
                 Ok(Action::None)
             }