Sample Prolog

This is an example Prolog project used in Daytona.

2 differents Prolog environments are being installed:

• GNU Prolog (gprolog)
• SWI-Prolog (swipl)

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🚀 Getting Started

Open Using Daytona

1. Install Daytona: Follow the Daytona installation guide.

2. Create the Workspace:

   daytona create https://github.com/daytonaio/sample-prolog

3. Verify Prolog environment version

$ gprolog --version
Prolog top-Level (GNU Prolog) x.y.z

$ swipl --version
SWI-Prolog version x.y.z for x86_64-linux

3. Open main.pro (in Visual Studio Code change bottom right "Plain Text" to "Prolog") (this will be required until sazzledazzle/prolog-runner#1 is not fixed)

Look at facts and rules which have been defined in main.pro.

4. Start the Application as a script with swipl:

Create a new Terminal by pressing on "+"

Cick on "Run Prolog File" to execute this file.

It should run

$ swipl -q -f "/workspaces/sample-prolog/main.pro" -t halt.

and display

Test grandparent(john, ann): true
Test sibling(ann, pat): true
Test ancestor(john, jim): true
Mary's children: [ann,pat]

5. Start the application as a script with gprolog:

$ gprolog
GNU Prolog 1.4.5 (64 bits)
Compiled Feb 23 2020, 20:14:50 with gcc
By Daniel Diaz
Copyright (C) 1999-2020 Daniel Diaz
| ?- [main].
compiling /workspaces/sample-prolog/main.pro for byte code...
/workspaces/sample-prolog/main.pro compiled, 49 lines read - 4240 bytes written, 51 ms
Test grandparent(john, ann): true
Test sibling(ann, pat): true
Test ancestor(john, jim): true
Mary's children: [ann,pat]

(4 ms) yes

Use CTRL+D to quit interpreter.

You can also run main.pro script like so:

$ gprolog --consult-file main.pro

6. Test gprolog or swipl as REPL (Read–eval–print loop).

Exemple with gprolog. Define facts and rules.

/* ... */ are multiline comments and % ... after a command is a single comment.

$ gprolog

| ?- /*
      Facts about parent relationships
      */
      assertz(parent(john, mary)). % john is parent of mary
yes
| ?- assertz(parent(john, tom)). % john is parent of tom
yes
| ?- assertz(parent(mary, ann)). % mary is parent of ann
yes
| ?- assertz(parent(mary, pat)). % mary is parent of pat
yes
| ?- assertz(parent(tom, jim)). % tom is parent of jim
yes
| ?- /*
      Rules
      */ assertz((grandparent(X, Z) :- parent(X, Y), parent(Y, Z))). % X is grandparent of Z if X is parent of Y and Y is parent of Z
yes
| ?- assertz((sibling(X, Y) :- parent(Z, X), parent(Z, Y), X \= Y)). % X is sibling of Y if they share a parent and are not the same person
yes
| ?- assertz((ancestor(X, Y) :- parent(X, Y))). % X is ancestor of Y if X is parent of Y
yes
| ?- assertz((ancestor(X, Y) :- parent(X, Z), ancestor(Z, Y))). % or X is parent of someone who is ancestor of Y
yes

Than queries:

| ?- grandparent(john, ann).
true ?

yes
| ?- sibling(ann, pat).
true ?

yes
| ?- ancestor(john, jim).

true ?

yes
| ?- findall(X, parent(mary, X), Children).

Children = [ann,pat]

(1 ms) yes

To quit interpreter :

| ?- halt.

Similiar REPL usage can be done with SWI-Prolog but be aware that

?- asserta(parent(alice, bob)).  % adds at beginning
?- assertz(parent(carol, dave)). % adds at end
?- assert(parent(eve, frank)).   % same as assertz in SWI-Prolog

The order can matter because Prolog searches clauses in the order they were added, which can affect:

• Performance (earlier clauses are checked first)
• Results (when multiple solutions exist)

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✨ Features

standardized development environment with devcontainers