Add and_then methods for EitherOrBoth

Author: Avi-D-coder

src/either_or_both.rs

@@ -132,4 +132,28 @@ impl<A, B> EitherOrBoth<A, B> {
             Both(a, b) => Both(f(a), g(b)),
         }
     }
+
+    /// Apply the function `f` on the value `b` in `Right(b)` or `Both(a, _)` variants if it is
+    /// present.
+    pub fn left_and_then<F, L>(self, f: F) -> EitherOrBoth<L, B>
+    where
+        F: FnOnce(A) -> EitherOrBoth<L, B>,
+    {
+        match self {
+            Left(a) | Both(a, _) => f(a),
+            Right(b) => Right(b),
+        }
+    }
+
+    /// Apply the function `f` on the value `a`
+    /// in `Left(a)` or `Both(a, _)` variants if it is present.
+    pub fn right_and_then<F, R>(self, f: F) -> EitherOrBoth<A, R>
+    where
+        F: FnOnce(B) -> EitherOrBoth<A, R>,
+    {
+        match self {
+            Left(a) => Left(a),
+            Right(b) | Both(_, b) => f(b),
+        }
+    }
 }