Moved rust code to its own cargo

.gitignore

@@ -1,3 +1,4 @@
 book
 .DS_Store
 listings/target
+target

src/software_development/is-leap-year.md

@@ -5,14 +5,7 @@
 **Rust**
 
 ```rust
-#let year = 2020;
-let is_leap = match (year % 400, year % 100, year % 4) {
-    (0, _, _) => true,
-    (_, 0, _) => false,
-    (_, _, 0) => true,
-    _ => false,
-};
-#println!("Year {} is a leap year: {}", year, is_leap);
+{{#rustdoc_include is-leap-year/src/main.rs:2:7}}
 ```
 
 ### Notes
@@ -23,40 +16,6 @@ The rules for determining if a year is a **leap year**:
 - but years divisible by 100 are **not** leap years,
 - but years divisible by 400 are leap years.
 
-### Test cases
-
-```rust,no_run,ignore
-#[cfg(test)]
-mod sample_tests {
-    use super::is_leap_year;
-
-    fn do_test(year: i32, expected: bool) {
-        let actual = is_leap_year(year);
-        assert_eq!(actual, expected, "\nYour result (left) does not match the expected output (right) for the year {year:?}");
-    }
-
-    #[test]
-    fn year_2020_is_a_leap_year() {
-        do_test(2020, true);
-    }
-
-    #[test]
-    fn year_2000_is_a_leap_year() {
-        do_test(2000, true);
-    }
-
-    #[test]
-    fn year_2015_is_not_a_leap_year() {
-        do_test(2015, false);
-    }
-
-    #[test]
-    fn year_2100_is_not_a_leap_year() {
-        do_test(2100, false);
-    }
-}
-```
-
 ## Chrestomathy
 
 **SQL**

src/software_development/is-leap-year/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "is-leap-year"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/software_development/is-leap-year/src/main.rs

@@ -0,0 +1,42 @@
+fn is_leap_year(year: i32) -> bool {
+    match (year % 400, year % 100, year % 4) {
+        (0, _, _) => true,
+        (_, 0, _) => false,
+        (_, _, 0) => true,
+        _ => false,
+    }
+}
+
+fn main() {
+    println!("Year {} is a leap year: {}", 2020, is_leap_year(2020));
+}
+
+#[cfg(test)]
+mod sample_tests {
+    use super::is_leap_year;
+
+    fn do_test(year: i32, expected: bool) {
+        let actual = is_leap_year(year);
+        assert_eq!(actual, expected, "\nYour result (left) does not match the expected output (right) for the year {year:?}");
+    }
+
+    #[test]
+    fn year_2020_is_a_leap_year() {
+        do_test(2020, true);
+    }
+
+    #[test]
+    fn year_2000_is_a_leap_year() {
+        do_test(2000, true);
+    }
+
+    #[test]
+    fn year_2015_is_not_a_leap_year() {
+        do_test(2015, false);
+    }
+
+    #[test]
+    fn year_2100_is_not_a_leap_year() {
+        do_test(2100, false);
+    }
+}