homework3.txt

% Consider a tree whose nodes are stored as lists, and the first
% element is the value stored at that node, while the other elements are subtrees.
% Define a possibly concise function to find an element in the tree
% We suppose that trees are stored as lists [key, subtree_1, subtree_2, ...]
% e.g. [root,[a,[b,1,2,3],[c,2],[f,[g,x,y]]]]



% Define the pack function that returns a list of list, each sub-list contains the adiacent occurences of an atom.
% pack [1, 1, 1, 2, 3, 3, 1] -> [[1,1,1], [2], [3,3], [1]]  



% Define the encode function that returns a list of list, each sub-list contains an atom and the number of its adiacent occurences.
% encode [1, 1, 1, 2, 3, 3, 1] -> [[1, 3], [2,1], [3,2], [1,1]]  



% Define th decode function that takes an encoded list and returns the 'original' list.
% decode [[1, 3], [2,1], [3,2], [1,1]] -> [1, 1, 1, 2, 3, 3, 1] 


% Consider a binary tree e.g., 
%        5
%   2        8
% 1   3    6  11

% stored using the 'tree' term. tree has three parameters: a number, a left tree and a right tree. a leaf is represented using the empty atom. e.g.,

% tree(5, tree(2, tree(1, empty, empty), tree(3, empty, empty)), tree(8, tree(6, empty, empty), tree(11, empty, empty)))

% Given the following tree_singleton function:

tree_singleton(N,R) :- R = tree(N, empty, empty).

% Define the tree_insert function to insert a node value (a number) in a tree 
% tree_insert(N, CurrentTree, NewTree)


% Define the tree_elem function to find a node value in a tree 
% tree_elem(N, Tree)


% Define the tree_sum function to sum all the node values in a tree
% tree_sum(Tree, Sum)


% Define the tree_values function to return a list of all the values contained in a tree
% tree_values(Tree, List)