From 52fcc103e1ae61ae3bb2e686763c246e2a266004 Mon Sep 17 00:00:00 2001
From: Mahdi Dibaiee <mdibaiee@aol.com>
Date: Wed, 11 Oct 2017 20:53:34 +0330
Subject: [PATCH] post(typoclassopedia): Monad#intuition

---
 ...-09-27-typoclassopedia-exercise-answers.md | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/_posts/2017-09-27-typoclassopedia-exercise-answers.md b/_posts/2017-09-27-typoclassopedia-exercise-answers.md
index f0d160d..35d7854 100644
--- a/_posts/2017-09-27-typoclassopedia-exercise-answers.md
+++ b/_posts/2017-09-27-typoclassopedia-exercise-answers.md
@@ -630,3 +630,24 @@ instance Monad Maybe where
       (Var x) >>= f = Var (f x)
       (Node x) >>= f = Node (fmap f x)
     ```
+
+## Intuition
+
+### Exercises
+
+1. Implement `(>>=)` in terms of `fmap` (or `liftM`) and `join`.
+  
+    **Solution**:
+    
+    ```haskell
+    a >>= f = join (fmap f a)
+    ```
+    
+2. Now implement `join` and `fmap` (`liftM`) in terms of `(>>=)` and `return`.
+
+    **Solution**:
+    
+    ```haskell
+    fmap f a = a >>= (return . f)
+    join m = m >>= id
+    ```