feat(zero-sized): add EmptyStr, LeftArrow, RightArrow

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- next-header -->
 
+## [2.2.0] - 2024-05-21
+### Added
+- `auxiliary::EmptyStr`
+- `auxiliary::LeftArrow`
+- `auxiliary::RightArrow`
+
 ## [2.1.0] - 2024-05-15
 ### Added
 - `PrintableWrapper: Clone`
@@ -24,6 +30,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `PrintableTuple`
 
 <!-- next-url -->
+[2.2.0]: https://github.com/andrewsonin/printable/releases/tag/v2.2.0
 [2.1.0]: https://github.com/andrewsonin/printable/releases/tag/v2.1.0
 [2.0.0]: https://github.com/andrewsonin/printable/releases/tag/v2.0.0
 [1.0.0]: https://github.com/andrewsonin/printable/releases/tag/v1.0.0

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "printable"
-version = "2.1.0"
+version = "2.2.0"
 authors = ["Andrew Sonin <sonin.cel@yandex.ru>"]
 categories = ["value-formatting"]
 description = "Provides `std::fmt::Display` wrapper for iterators and tuples."

src/auxiliary.rs

@@ -35,3 +35,39 @@ impl Display for RightSquareBracket {
         f.write_char(']')
     }
 }
+
+/// Zero-sized type, which is displayed as empty string.
+#[derive(Debug, Clone, Copy)]
+#[repr(transparent)]
+pub struct EmptyStr;
+
+impl Display for EmptyStr {
+    #[inline]
+    fn fmt(&self, _f: &mut Formatter<'_>) -> std::fmt::Result {
+        Ok(())
+    }
+}
+
+/// Zero-sized type, which is displayed as `<-`.
+#[derive(Debug, Clone, Copy)]
+#[repr(transparent)]
+pub struct LeftArrow;
+
+impl Display for LeftArrow {
+    #[inline]
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str("<-")
+    }
+}
+
+/// Zero-sized type, which is displayed as `->`.
+#[derive(Debug, Clone, Copy)]
+#[repr(transparent)]
+pub struct RightArrow;
+
+impl Display for RightArrow {
+    #[inline]
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str("->")
+    }
+}