initial commit

exercises/04_traits/01_trait/Cargo.toml

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+[package]
+name = "trait_"
+version = "0.1.0"
+edition = "2021"

exercises/04_traits/01_trait/src/lib.rs

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+// Define a trait named `IsEven` that has a method `is_even` that returns a `true` if `self` is
+// even, otherwise `false`.
+//
+// Then implement the trait for `u32` and `i32`.
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_u32_is_even() {
+        assert!(42u32.is_even());
+        assert!(!43u32.is_even());
+    }
+
+    #[test]
+    fn test_i32_is_even() {
+        assert!(42i32.is_even());
+        assert!(!43i32.is_even());
+        assert!(0i32.is_even());
+        assert!(!(-1i32).is_even());
+    }
+}