diff --git a/src/env.rs b/src/env.rs
index b47a573..c5a0ae2 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -13,8 +13,8 @@ impl Env {
         }
     }
 
-    pub fn set(&mut self, sym: &str, val: MalType) {
-        self.data.insert(sym.to_string(), val);
+    pub fn set(&mut self, sym: &str, val: &MalType) {
+        self.data.insert(sym.to_string(), val.clone());
     }
 
     pub fn get(&self, sym: &String) -> MalRet {
diff --git a/src/eval.rs b/src/eval.rs
index 6a46e83..4f608aa 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -2,14 +2,14 @@ use crate::env::Env;
 use crate::types::MalType::*;
 use crate::types::{MalArgs, MalMap, MalRet, MalType};
 
-fn call_func(func: &MalType, args: MalArgs) -> MalRet {
+fn call_func(func: &MalType, args: &[MalType]) -> MalRet {
     match func {
         Fun(func) => func(args),
         _ => Err(format!("{:?} is not a function", func)),
     }
 }
 
-fn eval_func(list: MalType) -> MalRet {
+fn eval_func(list: &MalType) -> MalRet {
     match list {
         List(list) => {
             let func = &list[0];
@@ -18,7 +18,7 @@ fn eval_func(list: MalType) -> MalRet {
             } else {
                 &list[0..0]
             };
-            call_func(func, args.to_vec())
+            call_func(func, args)
         }
         _ => Err("YOU SHOULD NOT BE HERE".to_string()),
     }
@@ -31,17 +31,17 @@ pub fn eval(ast: &MalType, env: &Env) -> MalRet {
                 // Ok(Nil) // Should be the normal behavior
                 Ok(ast.clone())
             } else {
-                eval_func(eval_ast(ast.clone(), env)?)
+                eval_func(&eval_ast(ast, env)?)
             }
         }
-        _ => eval_ast(ast.clone(), env),
+        _ => eval_ast(ast, env),
     }
 }
 
-fn eval_collection(list: MalArgs, env: &Env) -> Result<MalArgs, String> {
+fn eval_collection(list: &MalArgs, env: &Env) -> Result<MalArgs, String> {
     let mut ret = MalArgs::new();
     for el in list {
-        match eval(&el, env) {
+        match eval(el, env) {
             Ok(val) => ret.push(val),
             Err(err) => return Err(err),
         }
@@ -49,12 +49,12 @@ fn eval_collection(list: MalArgs, env: &Env) -> Result<MalArgs, String> {
     Ok(ret)
 }
 
-fn eval_map(map: MalMap, env: &Env) -> MalRet {
+fn eval_map(map: &MalMap, env: &Env) -> MalRet {
     let mut ret = MalMap::new();
 
     for (k, v) in map {
-        match eval(&v, env) {
-            Ok(res) => ret.insert(k, res),
+        match eval(v, env) {
+            Ok(res) => ret.insert(k.to_string(), res),
             Err(err) => return Err(err),
         };
     }
@@ -62,12 +62,12 @@ fn eval_map(map: MalMap, env: &Env) -> MalRet {
     Ok(Map(ret))
 }
 
-fn eval_ast(ast: MalType, env: &Env) -> MalRet {
+fn eval_ast(ast: &MalType, env: &Env) -> MalRet {
     match ast {
-        Sym(sym) => env.get(&sym),
+        Sym(sym) => env.get(sym),
         List(list) => Ok(List(eval_collection(list, env)?)),
         Vector(vec) => Ok(Vector(eval_collection(vec, env)?)),
         Map(map) => eval_map(map, env),
-        _ => Ok(ast),
+        _ => Ok(ast.clone()),
     }
 }
diff --git a/src/types.rs b/src/types.rs
index 73ade89..777743a 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -7,7 +7,7 @@ pub enum MalType {
     List(MalArgs),
     Vector(MalArgs),
     Map(MalMap),
-    Fun(fn(MalArgs) -> MalRet),
+    Fun(fn(&[MalType]) -> MalRet),
     Sym(String),
     Key(String),
     Str(String),
@@ -78,7 +78,7 @@ fn if_number(val: &MalType) -> Result<isize, String> {
     }
 }
 
-pub fn int_op(set: isize, f: fn(isize, isize) -> isize, args: MalArgs) -> MalRet {
+pub fn int_op(set: isize, f: fn(isize, isize) -> isize, args: &[MalType]) -> MalRet {
     if args.is_empty() {
         return Ok(Int(set));
     }
@@ -98,13 +98,13 @@ use crate::env::Env;
 use MalType::Fun;
 
 pub fn env_init(env: &mut Env) {
-    env.set("quit", Fun(|_| exit(0)));
-    env.set("+", Fun(|a: MalArgs| int_op(0, |a, b| a + b, a)));
-    env.set("-", Fun(|a: MalArgs| int_op(0, |a, b| a - b, a)));
-    env.set("*", Fun(|a: MalArgs| int_op(1, |a, b| a * b, a)));
-    env.set("/", Fun(|a: MalArgs| int_op(1, |a, b| a / b, a)));
+    env.set("quit", &Fun(|_| exit(0)));
+    env.set("+", &Fun(|a: &[MalType]| int_op(0, |a, b| a + b, a)));
+    env.set("-", &Fun(|a: &[MalType]| int_op(0, |a, b| a - b, a)));
+    env.set("*", &Fun(|a: &[MalType]| int_op(1, |a, b| a * b, a)));
+    env.set("/", &Fun(|a: &[MalType]| int_op(1, |a, b| a / b, a)));
     env.set(
         "test",
-        Fun(|_| Ok(Str("This is a test function".to_string()))),
+        &Fun(|_| Ok(Str("This is a test function".to_string()))),
     );
 }