Prolog

Useful links

docu

Learn Prolog Now! guide

tools and online compilers

Online code IDE for prolog | SWISH

Online Prolog IDE | JDOODLE

examples

GitHub repo with lot of PROLOG examples

Install PROLOG

The following describes the installation process of PROLOG for Ubuntu:

Method 1: Using the official PPA

The full installation processes can be found on the official website.

Installing the stable release using debian-style packages:

sudo apt-get install software-properties-common
sudo apt-add-repository ppa:swi-prolog/stable
sudo apt-get update
sudo apt-get install swi-prolog

Method 2: Installing through snap:

Keep in mind snap is different from working with debian packages.

snap install swi-prolog		# install stable release

My own prolog query system

The usual process to work with PROLOG is described here | StackOverflow. This process involves writing predicates in a file, then loading the file while running the PROLOG interpreter to then be able to evaluate predicates. It means going through 5 steps each time you want to modify the base file predicates...

To simplify this process to running a single command to the terminal, the idea is to build query testing predicates that I have called test_<name of tested predicate>. This contains predicates being evaluated as well as writeln statements to keep track of what happens and what results are expected. Example:

test_ancestors :- 
    setof(X, ancestor(X, florian), L),
    write('ancestor(X, florian) ?- : '),
    writeln(L).

NOTE: Keep in mind that those query can only work by evaluation their predicates successfully from first to last one. So convert expected fails to not(fail) == success for the program to be executed normally. Example:

test_has_following_element_2 :-
    not(has_following_element(3, [1,2,3])),
    writeln("has_following_element(3, [1,2,3]) ?- failure as expected").

WARN: Keep in mind to call the query in the main query being executed at file interpretation:

%%% run:
:- initialization(main).
main:- 
    test_grandparent,
    test_ancestors,
    test_list_of_ancestors_1,
    test_list_of_ancestors_2,
    halt.

Run and execute directly in one command swipl <filepath.pl> in a terminal:

(base)  ❮ onyr ★  kenzae❯ ❮ alia❯❯ swipl exercices/lists.pl 
member(pierre,[annie,olivier,pierre,veronique]) ?- success as expected
member(X, [annie,olivier,pierre,veronique]) ?- : [annie,olivier,pierre,veronique]
concat([1,2,3],[4,5,6],[1,2,3,4,5,6]) ?- success as expected
has_following_element(3, [1,2,3,4]) ?- success as expected
has_following_element(3, [1,2,3]) ?- failure as expected
last_element(3, [1,2,3]) ?- success as expected
last_element(3, [1,2,3,4]) ?- failure as expected
has_preceding_element(3, [1,2,3]) ?- success as expected
has_preceding_element(1, [1,2,3]) ?- failure as expected
first_element(1, [1,2,3]) ?- success as expected
first_element(3, [1,2,3]) ?- failure as expected