Add specialization fn fold to Coalesce (1) tests

Author: phimuemue

tests/quick.rs

@@ -753,6 +753,29 @@ quickcheck! {
     }
 }
 
+quickcheck! {
+    fn dedup_via_coalesce(a: Vec<i32>) -> bool {
+        let mut b = a.clone();
+        b.dedup();
+        itertools::equal(
+            &b,
+            a
+                .iter()
+                .coalesce(|x, y| {
+                    if x==y {
+                        Ok(x)
+                    } else {
+                        Err((x, y))
+                    }
+                })
+                .fold(vec![], |mut v, n| {
+                    v.push(n);
+                    v
+                })
+        )
+    }
+}
+
 quickcheck! {
     fn equal_dedup(a: Vec<i32>) -> bool {
         let mut b = a.clone();

tests/test_std.rs

@@ -109,6 +109,26 @@ fn dedup() {
     assert_eq!(&xs_d, &ys);
 }
 
+#[test]
+fn coalesce() {
+    let data = vec![-1., -2., -3., 3., 1., 0., -1.];
+    let it = data.iter().cloned().coalesce(|x, y|
+        if (x >= 0.) == (y >= 0.) {
+            Ok(x + y)
+        } else {
+            Err((x, y))
+        }
+    );
+    itertools::assert_equal(it.clone(), vec![-6., 4., -1.]);
+    assert_eq!(
+        it.fold(vec![], |mut v, n| {
+            v.push(n);
+            v
+        }),
+        vec![-6., 4., -1.]
+    );
+}
+
 #[test]
 fn dedup_by() {
     let xs = [(0, 0), (0, 1), (1, 1), (2, 1), (0, 2), (3, 1), (0, 3), (1, 3)];