--- /dev/null
+use std::cmp::PartialEq;
+use std::ops::{Add, Sub, Mul};
+
+pub trait MyNum : Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self> + PartialEq + Clone {
+}
+
+#[derive(Clone, Debug)]
+pub struct MyInt {
+ pub val: isize
+}
+
+impl Add for MyInt {
+ type Output = MyInt;
+
+ fn add(self, other: MyInt) -> MyInt { mi(self.val + other.val) }
+}
+
+impl Sub for MyInt {
+ type Output = MyInt;
+
+ fn sub(self, other: MyInt) -> MyInt { mi(self.val - other.val) }
+}
+
+impl Mul for MyInt {
+ type Output = MyInt;
+
+ fn mul(self, other: MyInt) -> MyInt { mi(self.val * other.val) }
+}
+
+impl PartialEq for MyInt {
+ fn eq(&self, other: &MyInt) -> bool { self.val == other.val }
+
+ fn ne(&self, other: &MyInt) -> bool { !self.eq(other) }
+}
+
+impl MyNum for MyInt {}
+
+fn mi(v: isize) -> MyInt { MyInt { val: v } }