diff --git a/src/callable/function.rs b/src/callable/function.rs
new file mode 100644
index 0000000..73c1760
--- /dev/null
+++ b/src/callable/function.rs
@@ -0,0 +1,35 @@
+use crate::{
+    ast::Stmt,
+    callable::Callable,
+    environment::Env,
+    interpreter::{Interpreter, RuntimeError},
+    span::Spanned,
+    value::Value,
+};
+
+#[derive(Clone, Debug)]
+pub struct LoxFunction {
+    params: Vec<String>,
+    body: Vec<Spanned<Stmt>>,
+}
+
+impl LoxFunction {
+    pub fn new(params: Vec<String>, body: Vec<Spanned<Stmt>>) -> Self {
+        Self { params, body }
+    }
+}
+
+impl Callable for LoxFunction {
+    fn params(&self) -> Vec<String> {
+        self.params.clone()
+    }
+
+    fn call(&self, interpreter: &mut Interpreter, env: &Env) -> Result<Value, RuntimeError> {
+        for stmt in &self.body {
+            if let Some(return_value) = interpreter.execute_stmt(stmt, env)? {
+                return Ok(return_value);
+            }
+        }
+        Ok(Value::Nil)
+    }
+}
diff --git a/src/callable/mod.rs b/src/callable/mod.rs
new file mode 100644
index 0000000..14a1de8
--- /dev/null
+++ b/src/callable/mod.rs
@@ -0,0 +1,16 @@
+mod function;
+mod native;
+
+use std::fmt::Debug;
+
+use crate::{environment::Env, interpreter::Interpreter, interpreter::RuntimeError, value::Value};
+
+pub use function::LoxFunction;
+pub use native::NativeFunction;
+
+pub trait Callable: Debug {
+    fn params(&self) -> Vec<String> {
+        Vec::new()
+    }
+    fn call(&self, interpreter: &mut Interpreter, env: &Env) -> Result<Value, RuntimeError>;
+}
diff --git a/src/callable.rs b/src/callable/native.rs
similarity index 52%
rename from src/callable.rs
rename to src/callable/native.rs
index 51b6414..d4c2a56 100644
--- a/src/callable.rs
+++ b/src/callable/native.rs
@@ -3,51 +3,17 @@ use std::{
     time::SystemTime,
 };
 
-use crate::ast::Stmt;
-use crate::interpreter::Interpreter;
-use crate::span::Spanned;
-use crate::{environment::Env, interpreter::RuntimeError, value::Value};
-
-type CallableOutput = Result<Value, RuntimeError>;
-
-pub trait Callable: Debug {
-    fn params(&self) -> Vec<String> {
-        Vec::new()
-    }
-    fn call(&self, interpreter: &mut Interpreter, env: &Env) -> CallableOutput;
-}
-
-#[derive(Clone, Debug)]
-pub struct LoxFunction {
-    params: Vec<String>,
-    body: Vec<Spanned<Stmt>>,
-}
-
-impl LoxFunction {
-    pub fn new(params: Vec<String>, body: Vec<Spanned<Stmt>>) -> Self {
-        Self { params, body }
-    }
-}
-
-impl Callable for LoxFunction {
-    fn params(&self) -> Vec<String> {
-        self.params.clone()
-    }
-
-    fn call(&self, interpreter: &mut Interpreter, env: &Env) -> CallableOutput {
-        for stmt in &self.body {
-            if let Some(return_value) = interpreter.execute_stmt(stmt, env)? {
-                return Ok(return_value);
-            }
-        }
-        Ok(Value::Nil)
-    }
-}
+use crate::{
+    callable::Callable,
+    environment::Env,
+    interpreter::{Interpreter, RuntimeError},
+    value::Value,
+};
 
 pub struct NativeFunction {
     arity: usize,
     #[allow(clippy::type_complexity)]
-    implementation: Box<dyn Fn(&Env) -> CallableOutput>,
+    implementation: Box<dyn Fn(&Env) -> Result<Value, RuntimeError>>,
 }
 
 impl NativeFunction {