1 files changed, 48 insertions, 0 deletions
diff --git a/tests/ui/traits/monad.rs b/tests/ui/traits/monad.rs
new file mode 100644
index 000000000..5d0612cf8
--- /dev/null
+++ b/tests/ui/traits/monad.rs
@@ -0,0 +1,48 @@
+// run-pass
+
+#![allow(non_camel_case_types)]
+
+
+
+trait vec_monad<A> {
+    fn bind<B, F>(&self, f: F ) -> Vec<B> where F: FnMut(&A) -> Vec<B> ;
+}
+
+impl<A> vec_monad<A> for Vec<A> {
+    fn bind<B, F>(&self, mut f: F) -> Vec<B> where F: FnMut(&A) -> Vec<B> {
+        let mut r = Vec::new();
+        for elt in self {
+            r.extend(f(elt));
+        }
+        r
+    }
+}
+
+trait option_monad<A> {
+    fn bind<B, F>(&self, f: F) -> Option<B> where F: FnOnce(&A) -> Option<B>;
+}
+
+impl<A> option_monad<A> for Option<A> {
+    fn bind<B, F>(&self, f: F) -> Option<B> where F: FnOnce(&A) -> Option<B> {
+        match *self {
+            Some(ref a) => { f(a) }
+            None => { None }
+        }
+    }
+}
+
+fn transform(x: Option<isize>) -> Option<String> {
+    x.bind(|n| Some(*n + 1) ).bind(|n| Some(n.to_string()) )
+}
+
+pub fn main() {
+    assert_eq!(transform(Some(10)), Some("11".to_string()));
+    assert_eq!(transform(None), None);
+    assert_eq!((vec!["hi".to_string()])
+        .bind(|x| vec![x.clone(), format!("{}!", x)] )
+        .bind(|x| vec![x.clone(), format!("{}?", x)] ),
+        ["hi".to_string(),
+         "hi?".to_string(),
+         "hi!".to_string(),
+         "hi!?".to_string()]);
+}