Logic programming with Prolog

The project consists of small logic programs written in Prolog language.

List of programs

• Cross Pair Counter: calculates cross pairs between two lists
• Integrate: numerical integration with Trapezoidal rule
• Times 3: triples the values in the list
• NFA: determines whether a given string belongs to the defined language patterns
• Pell numbers: generates a sequence of Pell numbers with a specified length
• Range product: calculates the product of all numbers within a specified range
• Romeo and Juliette: gives the answers based on facts and rules

How to execute

Use SWI-Prolog, available at https://www.swi-prolog.org, to execute the program. Follow these steps:

1. Open in SWI-Prolog:

   • Launch SWI-Prolog.
   • Open the program within the SWI-Prolog environment.

2. Using Command Line Arguments:

   • Interact with the program by providing requests as command-line arguments.

Program description

Cross Pair Counter

This program calculates cross pairs between two lists. Both lists must have the same length and an even number of elements:

AxB = $[[a_0, b_1], [b_0, a_1], [a_2, b_3], [b_2, a_3], ..., [a_{n-1}, b_n], [b_{n-1}, a_n]]$

where A = $[a_0, a_1, ..., a_n]$ and B = $[b_0, b_1, ..., b_n]$.

Input Example

To calculate cross pairs, use the following function:

cross_pair([1, 2, 3, 4, 5, 6], ['a', 'b', 'c', 'd', 'e', 'f'], AxB)

Integrate

The program is a Prolog implementation of numerical integration with Trapezoidal rule using function $f(y) = x^2$ .

Input Example

Use the function integrate in the following form:

integrate(A, B, N, F, R).

A: lower bound
B: upper bound
N: number of the subintervals
F: function 
R: result

Example: integrate(1, 2, 100000, f, R).

Times 3

This program operates on a list of numbers, transforming each number by tripling its value to create a new list. The program accepts a list of numbers as input and generates another list containing each number multiplied by 3.

Input example

To use the program, call the map predicate in following format:

map([1,2,3,4,5,10], times3, R).

NFA

This program serves as an implementation of a Nondeterministic Finite Automaton (NFA) designed to recognize strings in a specified language defined by the following patterns:

Pattern 1 (accept1): $c(b|aa) * (dc)?$
Pattern 2 (accept2): $a + (a|cd) * |(bc*)$

The program employs a Nondeterministic Finite Automaton (NFA) model to determine whether a given string belongs to the defined language patterns.

Input examples

accept1([c,b,b,a,a,d,c]). 
accept1([c,a,a,d,c]). 
accept1([c,a,a,b,b,b,a,a,d,c]).

accept2([a,a,a,c,d]). 
accept2([a,a,a,c,d,a]).  
accept2([a,a,a,c,d,a,c,d]). 
accept2([a,c,d,a,c,d]). 

Pell numbers

The program is designed to generate a sequence of Pell numbers with a specified length.

Pell numbers are a sequence of integers where each number (starting from the third term) is the sum of twice the preceding number and the number before that. The sequence starts with 0 and 1, followed by 2, 5, 12, 29, and so on.

Input example:

pell(8,P).

8: length of the sequence 
P: sequence of Pell numbers 

Note: if the output exceeds 8 numbers, you have the option to modify the default maximum depth using the following command:
set_prolog_flag(answer_write_options, [quoted(true), portray(false), max_depth(20), spacing(next_argument)]).

Range product

The program calculates the product of all numbers within a specified range.

Input example:

Provide the desired range as input to the program to calculate the product of numbers within that range in following form: range product(From, To, Res).

range_product(4,7,Res).

Romeo and Juliette

This Prolog logic program revolves around the story of Romeo and Juliette. It determines whether the relationship between Romeo and Juliette could lead to any dramatic outcomes.

Input examples:

To make requests, you can use following commands:

Is Romeo Monetecchi?

family(romeo, montecchi).

Is Juliette Capuleti?

family(giulietta, capuleti).

Are Montecchi and Capuleti enemies?

enemies(montecchi, capuleti).
enemies(capuleti, montecchi).

If Rome and Juliette are together, is there any drama?

drama(romeo, giulietta).
drama(giulietta, romeo).