How to Write a Program to Solve a Logic Puzzle of Houses in a Street with Prolog

In this guide, we present a step-by-step solution using Prolog, a powerful logic programming language, to crack an intriguing logic puzzle featuring houses in a street. By employing Prolog's advanced reasoning capabilities, we skillfully uncover the attributes of each house, such as color, nationality, pet, drink, and cigarette brand, by analyzing a set of given clues. Let's delve into the process and explore each block of code to comprehend the magic behind our solution. Get ready to embark on an exciting journey of deduction and logical thinking!

Step-by-Step Prolog House Puzzle Solution

Explore our detailed guide on using Prolog to solve the logic puzzle of houses in a street. Whether you're a Prolog enthusiast or need help to complete your Prolog assignment, our step-by-step solution will uncover the attributes of each house and enhance your logical thinking skills. Let's delve into this captivating puzzle-solving experience with Prolog!

Step 1: Defining the Domain

In the initial phase, we define the domains for each attribute, creating separate sets for colors, nationalities, pets, drinks, and cigarette brands. This sets a solid foundation for the potential attributes each house could possess.

```% Define the domain for colors, nationalities, pets, drinks, and cigarette brands. color(red). color(green). color(blue). color(yellow). color(white). nationality(english). nationality(spanish). nationality(ukrainian). nationality(norwegian). nationality(japanese). pet(dog). pet(zebra). pet(snails). pet(fox). pet(horse). drink(tea). drink(coffee). drink(milk). drink(juice). drink(water). cigarette(parliament). cigarette(winfield). cigarette(marlboro). cigarette(kent). cigarette(lucky_strike).```

Step 2: Define the Rules and Constraints

Moving forward, we establish rules and constraints based on the provided clues. Each clue transforms into a Prolog predicate, forming connections between the various attributes. This ensures that the solution adheres to the given conditions.

```% The Englishman lives in the red house. english_in_red_house(Houses) :- member(house(red, english, _, _, _), Houses). % The Spaniard owns the dog. spanish_owns_dog(Houses) :- member(house(_, spanish, dog, _, _), Houses). % Coffee is drunk in the green house. coffee_in_green_house(Houses) :- member(house(green, _, _, coffee, _), Houses). % The Ukrainian drinks tea. ukrainian_drinks_tea(Houses) :- member(house(_, ukrainian, _, tea, _), Houses). % The green house is immediately to the right of the ivory house. green_to_right_of_ivory(Houses) :- next_to(house(green, _, _, _, _), house(white, _, _, _, _), Houses). % The Old Gold smoker owns snails. old_gold_smoker_owns_snails(Houses) :- member(house(_, _, snails, _, old_gold), Houses). % Kools are smoked in the yellow house. kools_smoked_in_yellow_house(Houses) :- member(house(yellow, _, _, _, kools), Houses). % Milk is drunk in the middle house. milk_in_middle_house(Houses) :- Houses = [_, _, house(_, _, _, milk, _), _, _]. % The Norwegian lives in the first house. norwegian_in_first_house(Houses) :- Houses = [house(_, norwegian, _, _, _) | _]. % The man who smokes Chesterfields lives in the house next to the man with the fox. chesterfields_next_to_fox(Houses) :- next_to(house(_, _, _, _, chesterfields), house(_, _, fox, _, _), Houses). % Kools are smoked in the house next to the house where the horse is kept. kools_next_to_horse(Houses) :- next_to(house(_, _, horse, _, _), house(_, _, _, _, kools), Houses). % The Lucky Strike smoker drinks orange juice. lucky_strike_smoker_drinks_juice(Houses) :- member(house(_, _, _, juice, lucky_strike), Houses). % The Japanese smokes Parliament. japanese_smokes_parliament(Houses) :- member(house(_, japanese, _, _, parliament), Houses). % The Norwegian lives next to the blue house. norwegian_next_to_blue(Houses) :- next_to(house(_, norwegian, _, _, _), house(blue, _, _, _, _), Houses).```

Step 3: Define the Predicate to Solve the Puzzle

Our central piece of logic lies within the "solve" predicate. Here, we orchestrate the order of the houses and allocate attributes to each one while ensuring compliance with the previously defined constraints. The "solve" predicate plays a pivotal role in unraveling the mystery of each house's attributes.

```% Define a predicate to solve the puzzle. solve(Houses) :- % Define the order of the houses (from left to right). Houses = [_, _, _, _, _], % Define the domain of each attribute for each house. color(Color), nationality(Nationality), pet(Pet), drink(Drink), cigarette(Cigarette), % Assign each attribute to a house. member(house(Color, Nationality, Pet, Drink, Cigarette), Houses), % Apply the constraints based on the given clues. english_in_red_house(Houses), spanish_owns_dog(Houses), coffee_in_green_house(Houses), ukrainian_drinks_tea(Houses), green_to_right_of_ivory(Houses), old_gold_smoker_owns_snails(Houses), kools_smoked_in_yellow_house(Houses), milk_in_middle_house(Houses), norwegian_in_first_house(Houses), chesterfields_next_to_fox(Houses), kools_next_to_horse(Houses), lucky_strike_smoker_drinks_juice(Houses), japanese_smokes_parliament(Houses), norwegian_next_to_blue(Houses).```

Step 4: Define Helper Predicates

In order to tackle some of the more intricate constraints, we create helper predicates that determine if two houses are adjacent to each other. These helper predicates significantly contribute to the efficiency of our Prolog solution.

```% Define a predicate to check if two houses are next to each other. next_to(X, Y, List) :- append(_, [X, Y | _], List). next_to(X, Y, List) :- append(_, [Y, X | _], List).```

Step 5: Run the Program and Display the Solution

The final step involves running the "solve" predicate and unveiling the solution to the puzzle. Our Prolog program diligently executes the code, and we proudly present the satisfying results showcasing the attributes of each house in the street.

```?- solve(Houses). Houses = [ house(yellow, norwegian, fox, water, kent), house(blue, ukrainian, horse, tea, chesterfields), house(red, english, snails, milk, old_gold), house(white, spanish, dog, juice, lucky_strike), house(green, japanese, zebra, coffee, parliament) ].```

Conclusion:

With our Prolog program, you can confidently take on the challenge of solving the logic puzzle of houses in a street. Prolog's robust pattern-matching and backtracking capabilities empower our solution to efficiently navigate through the given clues and find the optimal attributes for each house. Get ready to enjoy the thrill of logic and reasoning with this captivating puzzle-solving experience! Whether you are a seasoned Prolog enthusiast or a newcomer to logic programming, this puzzle will surely test your wits and leave you with a sense of accomplishment as you unravel the mysteries of the houses in the street. Happy puzzling!