diff --git a/src/value/number/integer.rs b/src/value/number/integer.rs
new file mode 100644
index 0000000..56753d4
--- /dev/null
+++ b/src/value/number/integer.rs
@@ -0,0 +1,150 @@
+use std::fmt::{self, Display, UpperHex};
+use std::mem;
+use std::ops::{Add, AddAssign};
+
+use num_bigint::BigInt;
+use num_traits::{Signed, ToPrimitive, Zero};
+
+#[derive(Eq, PartialEq)]
+pub(crate) enum Integer {
+    Machine(i64),
+    Big(BigInt),
+}
+
+impl Integer {
+    pub fn abs(&self) -> Self {
+        match self {
+            Self::Machine(v) => Self::Machine(v.abs()),
+            Self::Big(v) => Self::Big(v.abs()),
+        }
+    }
+
+    pub fn is_ten(&self) -> bool {
+        match self {
+            Self::Machine(10) => true,
+            Self::Machine(..) => false,
+            Self::Big(v) => v == &BigInt::from(10),
+        }
+    }
+}
+
+impl Default for Integer {
+    fn default() -> Self {
+        Self::zero()
+    }
+}
+
+impl UpperHex for Integer {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Machine(v) => write!(f, "{:02X}", v),
+            Self::Big(v) => write!(f, "{:02X}", v),
+        }
+    }
+}
+
+impl Add for Integer {
+    type Output = Self;
+    fn add(self, rhs: Self) -> Self::Output {
+        match self {
+            Self::Machine(val1) => match rhs {
+                Self::Machine(val2) => match val1.checked_add(val2) {
+                    Some(v) => Self::Machine(v),
+                    None => Self::Big(BigInt::from(val1) + val2),
+                },
+                Self::Big(val2) => Self::Big(BigInt::from(val1) + val2),
+            },
+            Self::Big(val1) => match rhs {
+                Self::Big(val2) => Self::Big(val1 + val2),
+                Self::Machine(val2) => Self::Big(val1 + BigInt::from(val2)),
+            },
+        }
+    }
+}
+
+impl Add<BigInt> for Integer {
+    type Output = Self;
+    fn add(self, rhs: BigInt) -> Self::Output {
+        match self {
+            Self::Machine(v) => Self::Big(BigInt::from(v) + rhs),
+            Self::Big(v) => Self::Big(v + rhs),
+        }
+    }
+}
+
+impl Add<i32> for Integer {
+    type Output = Self;
+    fn add(self, rhs: i32) -> Self::Output {
+        match self {
+            Self::Machine(v) => match v.checked_add(rhs as i64) {
+                Some(v) => Self::Machine(v),
+                None => Self::Big(BigInt::from(v) + rhs),
+            },
+            Self::Big(v) => Self::Big(v + rhs),
+        }
+    }
+}
+
+impl AddAssign<i32> for Integer {
+    fn add_assign(&mut self, rhs: i32) {
+        let tmp = mem::take(self);
+        *self = tmp + rhs;
+    }
+}
+
+impl AddAssign for Integer {
+    fn add_assign(&mut self, rhs: Self) {
+        let tmp = mem::take(self);
+        *self = tmp + rhs;
+    }
+}
+
+impl Zero for Integer {
+    fn zero() -> Self {
+        Self::Machine(0)
+    }
+
+    fn is_zero(&self) -> bool {
+        match self {
+            Self::Machine(0) => true,
+            Self::Machine(..) => false,
+            Self::Big(v) => v.is_zero(),
+        }
+    }
+
+    fn set_zero(&mut self) {
+        *self = Self::zero()
+    }
+}
+
+impl Display for Integer {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Machine(v) => write!(f, "{}", v),
+            Self::Big(v) => write!(f, "{}", v),
+        }
+    }
+}
+
+impl ToPrimitive for Integer {
+    fn to_u8(&self) -> Option<u8> {
+        match self {
+            Self::Machine(v) => v.to_u8(),
+            Self::Big(v) => v.to_u8(),
+        }
+    }
+
+    fn to_u64(&self) -> Option<u64> {
+        match self {
+            Self::Machine(v) => v.to_u64(),
+            Self::Big(v) => v.to_u64(),
+        }
+    }
+
+    fn to_i64(&self) -> std::option::Option<i64> {
+        match self {
+            Self::Machine(v) => Some(*v),
+            Self::Big(v) => v.to_i64(),
+        }
+    }
+}
diff --git a/src/value/number.rs b/src/value/number/mod.rs
similarity index 83%
rename from src/value/number.rs
rename to src/value/number/mod.rs
index 9eaaf22..0f6dd12 100644
--- a/src/value/number.rs
+++ b/src/value/number/mod.rs
@@ -1,6 +1,6 @@
 use std::cmp::Ordering;
 use std::convert::{From, TryFrom};
-use std::fmt::{self, Display, UpperHex, Write};
+use std::fmt::{self, Display, Write};
 use std::mem;
 use std::ops::{
     Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Rem, RemAssign, Sub, SubAssign,
@@ -8,156 +8,14 @@ use std::ops::{
 
 use num_bigint::BigInt;
 use num_rational::{BigRational, Rational64};
-use num_traits::{
-    CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, Num, One, Signed, ToPrimitive, Zero,
-};
+use num_traits::{CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, Num, One, Signed, Zero};
+
+use integer::Integer;
+
+mod integer;
 
 const PRECISION: usize = 10;
 
-#[derive(Eq, PartialEq)]
-pub(crate) enum Integer {
-    Machine(i64),
-    Big(BigInt),
-}
-
-impl Default for Integer {
-    fn default() -> Self {
-        Self::zero()
-    }
-}
-
-impl UpperHex for Integer {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Machine(v) => write!(f, "{:02X}", v),
-            Self::Big(v) => write!(f, "{:02X}", v),
-        }
-    }
-}
-
-impl Add for Integer {
-    type Output = Self;
-    fn add(self, rhs: Self) -> Self::Output {
-        match self {
-            Self::Machine(val1) => match rhs {
-                Self::Machine(val2) => match val1.checked_add(val2) {
-                    Some(v) => Self::Machine(v),
-                    None => Self::Big(BigInt::from(val1) + val2),
-                },
-                Self::Big(val2) => Self::Big(BigInt::from(val1) + val2),
-            },
-            Self::Big(val1) => match rhs {
-                Self::Big(val2) => Self::Big(val1 + val2),
-                Self::Machine(val2) => Self::Big(val1 + BigInt::from(val2)),
-            },
-        }
-    }
-}
-
-impl Add<BigInt> for Integer {
-    type Output = Self;
-    fn add(self, rhs: BigInt) -> Self::Output {
-        match self {
-            Self::Machine(v) => Self::Big(BigInt::from(v) + rhs),
-            Self::Big(v) => Self::Big(v + rhs),
-        }
-    }
-}
-
-impl Add<i32> for Integer {
-    type Output = Self;
-    fn add(self, rhs: i32) -> Self::Output {
-        match self {
-            Self::Machine(v) => match v.checked_add(rhs as i64) {
-                Some(v) => Self::Machine(v),
-                None => Self::Big(BigInt::from(v) + rhs),
-            },
-            Self::Big(v) => Self::Big(v + rhs),
-        }
-    }
-}
-
-impl AddAssign<i32> for Integer {
-    fn add_assign(&mut self, rhs: i32) {
-        let tmp = mem::take(self);
-        *self = tmp + rhs;
-    }
-}
-
-impl AddAssign for Integer {
-    fn add_assign(&mut self, rhs: Self) {
-        let tmp = mem::take(self);
-        *self = tmp + rhs;
-    }
-}
-
-impl Zero for Integer {
-    fn zero() -> Self {
-        Self::Machine(0)
-    }
-
-    fn is_zero(&self) -> bool {
-        match self {
-            Self::Machine(0) => true,
-            Self::Machine(..) => false,
-            Self::Big(v) => v.is_zero(),
-        }
-    }
-
-    fn set_zero(&mut self) {
-        *self = Self::zero()
-    }
-}
-
-impl Integer {
-    fn abs(&self) -> Self {
-        match self {
-            Self::Machine(v) => Self::Machine(v.abs()),
-            Self::Big(v) => Self::Big(v.abs()),
-        }
-    }
-
-    fn is_ten(&self) -> bool {
-        match self {
-            Self::Machine(10) => true,
-            Self::Machine(..) => false,
-            Self::Big(v) => v == &BigInt::from(10),
-        }
-    }
-}
-
-impl Display for Integer {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Machine(v) => write!(f, "{}", v),
-            Self::Big(v) => write!(f, "{}", v),
-        }
-    }
-}
-
-impl ToPrimitive for Integer {
-    fn to_u8(&self) -> Option<u8> {
-        match self {
-            Self::Machine(v) => v.to_u8(),
-            Self::Big(v) => v.to_u8(),
-        }
-    }
-
-    fn to_u64(&self) -> Option<u64> {
-        match self {
-            Self::Machine(v) => v.to_u64(),
-            Self::Big(v) => v.to_u64(),
-        }
-    }
-
-    fn to_i64(&self) -> std::option::Option<i64> {
-        match self {
-            Self::Machine(v) => Some(*v),
-            Self::Big(v) => v.to_i64(),
-        }
-    }
-}
-
 #[derive(Clone, Eq, PartialEq, Ord)]
 pub(crate) enum Number {
     Machine(Rational64),