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Here we give out a procedure where the tree is rotated to the left so that the root becomes the left-most element and the leaves are moved to the right:

?View Code PROLOG1
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show(Tree):-
 show2(Tree,0).
 
show2(nil,_).
 
show2(t(Left,X,Right),Indent):-
 Ind2 is Indent + 2,
 show2(Right,Ind2),
 tab(Indent),write(X),nl,
 show2(Left,Ind2).

A way to represent a tree in Prolog could be:
t(t(nil,1,nil), 2, t(t(nil,3,nil),4,nil))

However, a binary tree is the one that is ordered from left to right accoriding to a relation. The general method for searching in the binary dictionary is:
-if X is the root of D then X has been found, otherwise
-if X is less than [...]

A list can be sorted if there is an ordering relation in between the terms. For example, here is an ordering relation:
gt(X,Y):- X > Y.
or for alphabetical order:
gt(X,Y):- X@>Y.

First we examine bubblesort. To sort a list:
- Find two adjacent elements, X and Y,in list such that gt(X,Y) is satisfied and swap X and Y in [...]

Note: This example is taken from Prolog: Programming for Artificial Intelligence by Ivan Bratko

An example of a cryptarithmetic puzzle is

   DONALD

   GERALD

+________

   ROBERT

Note that all letters have to be assigned different digits.  We need to define a relationship sum(N1,N2,N) where N1,N2, and N represent the three numbers that give the solution to the puzzle. However, [...]

The aim of this problem is to place eight queens on the empty chessboard in such a way that no queen attacks any other one. There will be three distinct solutions given.

Solution 1

At first, we need to define a representation of the board. Each square of chessboard can be represented by a pair of X and [...]