diff --git a/examples/doc_macro_show.rs b/examples/doc_macro_show.rs
index 36635f1..a12244c 100644
--- a/examples/doc_macro_show.rs
+++ b/examples/doc_macro_show.rs
@@ -10,7 +10,7 @@ fn main() {
     // This will write "1 2\n3 4\n" to the standard output.
     show!([[1, 2], [3, 4]]);
     // This will write "1, 2\n3, 4\n" to the standard output.
-    show!([[1, 2], [3, 4]], sep=["\n", ", "]);
+    show!([[1, 2], [3, 4]], sep = ["\n", ", "]);
     // This will write "1, 2\n3, 4!" to the standard output.
-    show!([[1, 2], [3, 4]], sep=["\n", ", "], end="!");
+    show!([[1, 2], [3, 4]], sep = ["\n", ", "], end = "!");
 }
diff --git a/src/write/mod.rs b/src/write/mod.rs
index f39fd17..df1af2e 100644
--- a/src/write/mod.rs
+++ b/src/write/mod.rs
@@ -67,18 +67,6 @@ pub trait WriteInto: Rank {
     }
 }
 
-// impl<T: WriteOneInto> WriteInto for T {
-//     #[inline]
-//     fn try_write_into_with_sep<S: Write + ?Sized>(
-//         &self,
-//         s: &mut S,
-//         sep: &[impl Separator],
-//     ) -> Result<()> {
-//         debug_assert!(sep.is_empty());
-//         self.try_write_one_into(s)
-//     }
-// }
-
 impl<T: WriteInto + ?Sized> WriteInto for &T {
     #[inline]
     fn try_write_into_with_sep<S: Write + ?Sized>(
diff --git a/src/write/sep_by.rs b/src/write/sep_by.rs
index 474c3c9..8e2d954 100644
--- a/src/write/sep_by.rs
+++ b/src/write/sep_by.rs
@@ -70,7 +70,6 @@ impl<I: Iterator<Item = T> + Clone, T: WriteInto, S: Separator + ?Sized> WriteIn
         residual: &[impl Separator],
     ) -> super::Result {
         let mut iter = self.iter.clone();
-        // eprintln!("sep: {:?}; residual: {:?}", self.sep, residual);
         if let Some(first) = iter.next() {
             first.try_write_into_with_sep(s, residual)?;
         }
diff --git a/src/write/separator.rs b/src/write/separator.rs
index fc3d09e..5e8bc08 100644
--- a/src/write/separator.rs
+++ b/src/write/separator.rs
@@ -37,45 +37,6 @@ pub trait GetDefaultSeparator {
     const DEFAULT_SEPARATOR: &'static [Self::Separator];
 }
 
-// impl<T0: Rank0 + ?Sized> GetDefaultSeparator for T0 {
-//     type Separator = &'static str;
-//     const DEFAULT_SEPARATOR: &'static [&'static str] = &[];
-// }
-
-// macro_rules! impl_rank1 {
-//     ($ty:ty, $($tt:tt)*) => {
-//         impl<T0: Rank0, $($tt)*> GetDefaultSeparator for $ty {
-//             type Separator = &'static str;
-//             const DEFAULT_SEPARATOR: &'static [&'static str] = &[" "];
-//         }
-//     };
-// }
-
-// impl_rank1!(Vec<T0>,);
-// impl_rank1!([T0; N], const N: usize);
-// impl_rank1!([T0],);
-
-// macro_rules! impl_rank2 {
-//     ($ty:ty, $($tt:tt)*) => {
-//         impl<T0: Rank0, $($tt)*> GetDefaultSeparator for $ty {
-//             type Separator = &'static str;
-//             const DEFAULT_SEPARATOR: &'static [&'static str] = &[" ", "\n"];
-//         }
-//     };
-// }
-
-// impl_rank2!(Vec<Vec<T0>>, );
-// impl_rank2!([Vec<T0>], );
-// impl_rank2!([Vec<T0>; N], const N: usize);
-
-// impl_rank2!(Vec<[T0; M]>, const M: usize);
-// impl_rank2!([[T0; M]], const M: usize);
-// impl_rank2!([[T0; M]; N], const M: usize, const N: usize);
-
-// impl_rank2!(Vec<&[T0]>, );
-// impl_rank2!([&[T0]], );
-// impl_rank2!([&[T0]; N], const N: usize);
-
 const fn get_rank(rank: usize, space: bool) -> &'static [&'static str] {
     match (rank, space) {
         (0, _) => &[],
diff --git a/tests/array.rs b/tests/array.rs
index 4ce4471..5673ce8 100644
--- a/tests/array.rs
+++ b/tests/array.rs
@@ -121,13 +121,22 @@ fn display() {
     assert_eq!(s.try_write_into_string_with_sep(&[" "]).unwrap(), "1 2 3");
 
     let s = [[1, 2, 3], [4, 5, 6]];
-    assert_eq!(s.try_write_into_string_with_sep(&["\n", " "]).unwrap(), "1 2 3\n4 5 6");
+    assert_eq!(
+        s.try_write_into_string_with_sep(&["\n", " "]).unwrap(),
+        "1 2 3\n4 5 6",
+    );
 
     let s = [[1, 2], [3, 4]];
-    assert_eq!(s.try_write_into_string_with_sep(&["\n", " "]).unwrap(), "1 2\n3 4");
+    assert_eq!(
+        s.try_write_into_string_with_sep(&["\n", " "]).unwrap(),
+        "1 2\n3 4",
+    );
 
     let s = [[1, 2]];
-    assert_eq!(s.try_write_into_string_with_sep(&["\n", " "]).unwrap(), "1 2");
+    assert_eq!(
+        s.try_write_into_string_with_sep(&["\n", " "]).unwrap(),
+        "1 2",
+    );
 
     let s: [[usize; 0]; 0] = [];
     assert_eq!(s.try_write_into_string_with_sep(&[" "]).unwrap(), "");
diff --git a/tests/slice.rs b/tests/slice.rs
index e69de29..bfb1053 100644
--- a/tests/slice.rs
+++ b/tests/slice.rs
@@ -0,0 +1,27 @@
+use iof::{show, unwrap, WriteInto};
+
+#[test]
+fn write_into() {
+    let buf = unwrap!([1, 2, 3, 4].as_slice().try_write_into_string());
+    assert_eq!(buf, "1 2 3 4");
+    let buf = unwrap!([1, 2].as_slice().try_write_into_string());
+    assert_eq!(buf, "1 2");
+    let buf = unwrap!([1].as_slice().try_write_into_string());
+    assert_eq!(buf, "1");
+    let buf = unwrap!([0i32; 0].as_slice().try_write_into_string());
+    assert_eq!(buf, "");
+
+    let buf = unwrap!(['1', '2', '3', '4'].as_slice().try_write_into_string());
+    assert_eq!(buf, "1234");
+    let buf = unwrap!(['1', '2'].as_slice().try_write_into_string());
+    assert_eq!(buf, "12");
+    let buf = unwrap!(['1'].as_slice().try_write_into_string());
+    assert_eq!(buf, "1");
+    let buf = unwrap!(['1'; 0].as_slice().try_write_into_string());
+    assert_eq!(buf, "");
+}
+
+#[test]
+fn show() {
+    show!([1, 2, 3, 4].as_slice());
+}
diff --git a/tests/string.rs b/tests/string.rs
index cdcbdae..b2b457e 100644
--- a/tests/string.rs
+++ b/tests/string.rs
@@ -159,5 +159,8 @@ fn string() {
     let mut buf = Cursor::new(Vec::new());
     show!("Hello, World!", end = "" => &mut buf);
     show!("🦀🦀🦀", => &mut buf);
-    assert_eq!(unwrap!(String::from_utf8(buf.into_inner())), "Hello, World!🦀🦀🦀\n");
+    assert_eq!(
+        unwrap!(String::from_utf8(buf.into_inner())),
+        "Hello, World!🦀🦀🦀\n",
+    );
 }