additional exercise in ch9

Author: la-yumba

Exercises/Chapter09/Exercises.cs

@@ -1,15 +1,20 @@
+using NUnit.Framework;
+using System;
+
 using LaYumba.Functional;
 using LaYumba.Functional.Data.LinkedList;
 using static LaYumba.Functional.Data.LinkedList.LinkedList;
 
-using NUnit.Framework;
-using System;
+using LaYumba.Functional.Data.BinaryTree;
+using static LaYumba.Functional.Data.BinaryTree.Tree;
 
 namespace Exercises.Chapter9
 {
    static class Exercises
    {
-      // LISTS: implement functions to work with the singly linked List defined in this chapter:
+      // LISTS
+
+      // Implement functions to work with the singly linked List defined in this chapter:
       // Tip: start by writing the function signature in arrow-notation
 
       // InsertAt inserts an item at the given index
@@ -28,13 +33,24 @@ static class Exercises
       // DropWhile: 
 
       // number of new objects required: 
+      // InsertAt: 
+      // RemoveAt: 
+      // TakeWhile: 
+      // DropWhile: 
 
       // TakeWhile and DropWhile are useful when working with a list that is sorted 
       // and you’d like to get all items greater/smaller than some value; write implementations 
       // that take an IEnumerable rather than a List
 
 
-      // TREES: Implement a LabelTree type, where each node has a label of type string and a list of subtrees; 
+      // TREES
+
+      // Is it possible to define `Bind` for the binary tree implementation shown in this
+      // chapter? If so, implement `Bind`, else explain why it’s not possible (hint: start by writing
+      // the signature; then sketch binary tree and how you could apply a tree-returning funciton to
+      // each value in the tree).
+
+      // Implement a LabelTree type, where each node has a label of type string and a list of subtrees; 
       // this could be used to model a typical navigation tree or a cateory tree in a website
 
       // Imagine you need to add localization to your navigation tree: you're given a `LabelTree` where

Exercises/Chapter09/Solutions.cs

@@ -5,6 +5,9 @@
 using LaYumba.Functional.Data.LinkedList;
 using static LaYumba.Functional.Data.LinkedList.LinkedList;
 
+using LaYumba.Functional.Data.BinaryTree;
+using static LaYumba.Functional.Data.BinaryTree.Tree;
+
 namespace Exercises.Chapter9.Solutions
 {
    static class Solutions
@@ -55,6 +58,16 @@ static List<T> DropWhile<T>(this List<T> @this, Func<T, bool> pred)
 
       // Answer: see LaYumba.Functional.EnumerableExt
 
+
+      // Is it possible to define `Bind` for the binary tree implementation shown in this
+      // chapter? If so, implement `Bind`:
+
+      static Tree<R> Bind<T, R>(this Tree<T> tree, Func<T, Tree<R>> f)
+         => tree.Match(
+               Leaf: f,
+               Branch: (l, r) => Branch(l.Bind(f), r.Bind(f))
+            );
+
    }
 
    // Implement a LabelTree type, where each node has a label of type string and a list of subtrees;