diff --git a/src/evaluator/mod.rs b/src/evaluator/mod.rs
index b86efdb..7aa2192 100644
--- a/src/evaluator/mod.rs
+++ b/src/evaluator/mod.rs
@@ -17,8 +17,8 @@ use crate::object::null::Null;
 use crate::object::r#macro::quote::Quote;
 use crate::object::return_value::ReturnValue;
 use crate::object::string::StringObj;
-use crate::object::ObjectType::{ArrayObj, HashObj, IntegerObj};
-use crate::object::{Object, ObjectInterface, ObjectType};
+use crate::object::ObjectType;
+use crate::object::{Object, ObjectInterface};
 use crate::{FALSE, NULL, TRUE};
 use log::trace;
 use std::collections::BTreeMap;
@@ -191,7 +191,7 @@ fn eval_block_statement(block: &BlockStatement, env: &mut Environment) -> anyhow
         trace!("[eval_block_statement] result is ({:?})", result);
         match result.clone() {
             Object::ReturnValue(value) => {
-                if value.object_type() == ObjectType::ReturnObj {
+                if value.object_type() == ObjectType::Return {
                     return Ok(value.into());
                 }
             }
@@ -288,7 +288,7 @@ fn eval_bang_operator_expression(right: Object) -> anyhow::Result<Object> {
 fn eval_minus_prefix_operator_expression(right: Object) -> anyhow::Result<Object> {
     match right {
         Object::Integer(value) => Ok(Integer::new(-value.value()).into()),
-        value if value.object_type() != IntegerObj => Ok(Null.into()),
+        value if value.object_type() != ObjectType::Integer => Ok(Null.into()),
         _ => unimplemented!(),
     }
 }
@@ -317,9 +317,9 @@ fn eval_index_expression(left: Object, index: Object) -> anyhow::Result<Object>
         left,
         index
     );
-    if left.object_type() == ArrayObj && index.object_type() == IntegerObj {
+    if left.object_type() == ObjectType::Array && index.object_type() == ObjectType::Integer {
         eval_array_index_expression(left, index)
-    } else if left.object_type() == HashObj {
+    } else if left.object_type() == ObjectType::Hash {
         eval_hash_index_expression(left, index)
     } else {
         Err(Error::IndexOperatorNotSupported(left.object_type().to_string()).into())
diff --git a/src/object/array.rs b/src/object/array.rs
index a26b0d1..b17bd44 100644
--- a/src/object/array.rs
+++ b/src/object/array.rs
@@ -50,7 +50,7 @@ impl NodeInterface for Array {
 
 impl ObjectInterface for Array {
     fn object_type(&self) -> ObjectType {
-        ObjectType::ArrayObj
+        ObjectType::Array
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/boolean.rs b/src/object/boolean.rs
index f58f5e2..99d507b 100644
--- a/src/object/boolean.rs
+++ b/src/object/boolean.rs
@@ -20,7 +20,7 @@ impl Boolean {
 
 impl ObjectInterface for Boolean {
     fn object_type(&self) -> ObjectType {
-        ObjectType::BooleanObj
+        ObjectType::Boolean
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/built_in_function.rs b/src/object/built_in_function.rs
index f83b360..3e294d8 100644
--- a/src/object/built_in_function.rs
+++ b/src/object/built_in_function.rs
@@ -2,8 +2,8 @@ use crate::ast::NodeInterface;
 use crate::error::Error;
 use crate::object::array::Array;
 use crate::object::integer::Integer;
-use crate::object::ObjectType::ArrayObj;
-use crate::object::{Object, ObjectInterface, ObjectType};
+use crate::object::ObjectType;
+use crate::object::{Object, ObjectInterface};
 use crate::NULL;
 use std::fmt::{Display, Formatter};
 
@@ -63,7 +63,7 @@ pub fn array_first_element(args: Vec<Object>) -> anyhow::Result<Object> {
         .into());
     }
 
-    if args[0].object_type() != ArrayObj {
+    if args[0].object_type() != ObjectType::Array {
         return Err(Error::ArgumentFirstMustArray {
             got: args[0].object_type().to_string(),
         }
@@ -85,7 +85,7 @@ pub fn array_last_element(args: Vec<Object>) -> anyhow::Result<Object> {
         .into());
     }
 
-    if args[0].object_type() != ArrayObj {
+    if args[0].object_type() != ObjectType::Array {
         return Err(Error::ArgumentFirstMustArray {
             got: args[0].object_type().to_string(),
         }
@@ -110,7 +110,7 @@ pub fn array_rest_element(args: Vec<Object>) -> anyhow::Result<Object> {
         .into());
     }
 
-    if args[0].object_type() != ArrayObj {
+    if args[0].object_type() != ObjectType::Array {
         return Err(Error::ArgumentFirstMustArray {
             got: args[0].object_type().to_string(),
         }
@@ -136,7 +136,7 @@ pub fn array_push_element(args: Vec<Object>) -> anyhow::Result<Object> {
         .into());
     }
 
-    if args[0].object_type() != ArrayObj {
+    if args[0].object_type() != ObjectType::Array {
         return Err(Error::ArgumentFirstMustArray {
             got: args[0].object_type().to_string(),
         }
@@ -162,7 +162,7 @@ pub fn puts(args: Vec<Object>) -> anyhow::Result<Object> {
 
 impl ObjectInterface for Builtin {
     fn object_type(&self) -> ObjectType {
-        ObjectType::ArrayObj
+        ObjectType::Array
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/function.rs b/src/object/function.rs
index fc7759b..8da71f1 100644
--- a/src/object/function.rs
+++ b/src/object/function.rs
@@ -50,7 +50,7 @@ impl Display for Function {
 
 impl ObjectInterface for Function {
     fn object_type(&self) -> ObjectType {
-        ObjectType::FunctionObj
+        ObjectType::Function
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/hash.rs b/src/object/hash.rs
index 42732fc..33af4a5 100644
--- a/src/object/hash.rs
+++ b/src/object/hash.rs
@@ -46,7 +46,7 @@ impl Display for Hash {
 
 impl ObjectInterface for Hash {
     fn object_type(&self) -> ObjectType {
-        ObjectType::HashObj
+        ObjectType::Hash
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/integer.rs b/src/object/integer.rs
index ea1e18a..05fccee 100644
--- a/src/object/integer.rs
+++ b/src/object/integer.rs
@@ -20,7 +20,7 @@ impl Integer {
 
 impl ObjectInterface for Integer {
     fn object_type(&self) -> ObjectType {
-        ObjectType::IntegerObj
+        ObjectType::Integer
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/macro/quote.rs b/src/object/macro/quote.rs
index e9173f2..898cb6c 100644
--- a/src/object/macro/quote.rs
+++ b/src/object/macro/quote.rs
@@ -1,7 +1,7 @@
 use crate::ast::Node;
 use crate::ast::NodeInterface;
 use crate::error::Error;
-use crate::object::ObjectType::QueueObj;
+use crate::object::ObjectType::Queue;
 use crate::object::{Object, ObjectInterface, ObjectType};
 use std::fmt::{Display, Formatter};
 
@@ -38,7 +38,7 @@ impl NodeInterface for Quote {
 
 impl ObjectInterface for Quote {
     fn object_type(&self) -> ObjectType {
-        QueueObj
+        Queue
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/mod.rs b/src/object/mod.rs
index c0a34e8..3c4d267 100644
--- a/src/object/mod.rs
+++ b/src/object/mod.rs
@@ -25,31 +25,31 @@ pub mod string;
 
 #[derive(Debug, PartialEq, Eq)]
 pub enum ObjectType {
-    IntegerObj,
-    BooleanObj,
-    NullObj,
-    ReturnObj,
-    FunctionObj,
-    StringObj,
-    BuiltinObj,
-    ArrayObj,
-    HashObj,
-    QueueObj,
+    Integer,
+    Boolean,
+    Null,
+    Return,
+    Function,
+    String,
+    Builtin,
+    Array,
+    Hash,
+    Queue,
 }
 
 impl Display for ObjectType {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::IntegerObj => write!(f, "INTEGER"),
-            Self::BooleanObj => write!(f, "BOOLEAN"),
-            Self::NullObj => write!(f, "NULL"),
-            Self::ReturnObj => write!(f, "RETURN"),
-            Self::FunctionObj => write!(f, "FUNCTION"),
-            Self::StringObj => write!(f, "STRING"),
-            Self::BuiltinObj => write!(f, "BUILTIN"),
-            Self::ArrayObj => write!(f, "ARRAY"),
-            Self::HashObj => write!(f, "HASH"),
-            Self::QueueObj => write!(f, "QUOTE"),
+            Self::Integer => write!(f, "INTEGER"),
+            Self::Boolean => write!(f, "BOOLEAN"),
+            Self::Null => write!(f, "NULL"),
+            Self::Return => write!(f, "RETURN"),
+            Self::Function => write!(f, "FUNCTION"),
+            Self::String => write!(f, "STRING"),
+            Self::Builtin => write!(f, "BUILTIN"),
+            Self::Array => write!(f, "ARRAY"),
+            Self::Hash => write!(f, "HASH"),
+            Self::Queue => write!(f, "QUOTE"),
         }
     }
 }
diff --git a/src/object/null.rs b/src/object/null.rs
index 5f7470e..b0143fe 100644
--- a/src/object/null.rs
+++ b/src/object/null.rs
@@ -22,7 +22,7 @@ impl NodeInterface for Null {
 
 impl ObjectInterface for Null {
     fn object_type(&self) -> ObjectType {
-        ObjectType::NullObj
+        ObjectType::Null
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/return_value.rs b/src/object/return_value.rs
index c279df2..4c8c9d1 100644
--- a/src/object/return_value.rs
+++ b/src/object/return_value.rs
@@ -34,7 +34,7 @@ impl NodeInterface for ReturnValue {
 
 impl ObjectInterface for ReturnValue {
     fn object_type(&self) -> ObjectType {
-        ObjectType::ReturnObj
+        ObjectType::Return
     }
 
     fn inspect(&self) -> String {
diff --git a/src/object/string.rs b/src/object/string.rs
index b3cba97..c695974 100644
--- a/src/object/string.rs
+++ b/src/object/string.rs
@@ -26,7 +26,7 @@ impl Display for StringObj {
 
 impl ObjectInterface for StringObj {
     fn object_type(&self) -> ObjectType {
-        ObjectType::StringObj
+        ObjectType::String
     }
 
     fn inspect(&self) -> String {