Prolog Programming Exercises

Exercise 1: Basic Facts and Rules

Family Relationships

% Facts about family relationships
parent(tom, bob).
parent(tom, liz).
parent(bob, ann).
parent(bob, pat).
parent(pat, jim).

% Rule: X is a grandparent of Z if X is parent of Y and Y is parent of Z
grandparent(X,Z) :- parent(X,Y), parent(Y,Z).

% Rule: X and Y are siblings if they have the same parent
sibling(X,Y) :- parent(Z,X), parent(Z,Y), X \= Y.

Sample Queries

?- parent(tom, bob).
% true.

?- parent(bob, X).
% X = ann ;
% X = pat.

?- grandparent(tom, ann).
% true.

?- grandparent(tom, X).
% X = ann ;
% X = pat.

Exercise 2: List Operations

Basic List Predicates

% Check if X is a member of list L
member(X, [X|_]).
member(X, [_|T]) :- member(X, T).

% Append two lists
append([], L, L).
append([H|T], L, [H|R]) :- append(T, L, R).

% Find length of a list
length([], 0).
length([_|T], N) :- length(T, N1), N is N1 + 1.

Sample Queries

?- member(3, [1,2,3,4]).
% true.

?- append([1,2], [3,4], X).
% X = [1, 2, 3, 4].

?- length([a,b,c], X).
% X = 3.

Exercise 3: Knowledge Representation Example

Animal Classification

% Facts about animals
animal(dog).
animal(cat).
animal(robin).
animal(penguin).

% Facts about mammals
mammal(dog).
mammal(cat).

% Facts about birds
bird(robin).
bird(penguin).

% Facts about flying ability
can_fly(robin).

% Rules
warm_blooded(X) :- mammal(X).
warm_blooded(X) :- bird(X).

vertebrate(X) :- mammal(X).
vertebrate(X) :- bird(X).

% Complex rule
can_move_fast(X) :- mammal(X), can_run(X).
can_move_fast(X) :- bird(X), can_fly(X).

Key Insights from Exercises

1. Facts are simple statements that are always true
2. Rules use :- to define logical implications
3. Queries ask questions and Prolog finds all possible answers
4. Unification matches variables with values automatically
5. Backtracking finds multiple solutions by exploring alternatives

Running the Code

These examples can be run in SWI-Prolog:

1. Save code in a .pl file
2. Load with ?- [filename].
3. Run queries at the ?- prompt

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