Playground

There is a scryer based Prolog Playground 🤗

You can simply try Prolog at this simple website without installing anything — No more excuses not to try Prolog 😜

Usage

The Playground presents two inputs. A big textarea one on the left and a small one on the right of it.

In the big textarea you can enter your knowledge base (facts and rules).

Than you can use the small input marked with ?- to query them.

Examples

This awesome project is still quite new and at the moment unfortunatelly misses some good examples.

…if you like webdevelopment, maybe you want fix that ;)

Hello World

For traditional reasons let's start with printing "Hello World!".

Todo so, we don't need and facts in our knowledge base but only this query:


?-
write('Hello World!').


=>
Hello World!   true.

Be aware, that

you must not write ?- (This is only the prompt)
every fact, rule and query must end with a "." (dot character)

While "Hello Wordl!" are trivial examples in most programming languages, it is not the most typical in prolog. We later give an explanation how it works.

logicians and computer pioneers

To understand prolog, let's do some tasks typical for logic programming…

We use a knowlede base with very simple facts. Copy this into the big textarea on the left:


logician("Aristoteles").
logician("Charles Babbage").
logician("Kurt Gödel").
logician("David Hilbert").
logician("Gottlob Frege").
logician("Gottfried Wilhelm Leibniz").
logician("Blaise Pascal").
logician("Amir Pnueli").
logician("Emil Leon Post").
logician("Michael Oser Rabin").
logician("Bertrand Russell").
logician("Alfred Tarski").
logician("Alan Turing").
logician("Ludwig Wittgenstein").

computer_pioneer("Charles Babbage").
computer_pioneer("Noam Chomsky").
computer_pioneer("Alonzo Church").
computer_pioneer("Edsger Wybe Dijkstra").
computer_pioneer("Kurt Gödel").
computer_pioneer("Sir Charles Antony Richard Hoare").
computer_pioneer("Stephen Cole Kleene").
computer_pioneer("Donald Knuth").
computer_pioneer("Ada Lovelace").
computer_pioneer("Marvin Minsky").
computer_pioneer("John von Neumann").
computer_pioneer("Amir Pnueli").
computer_pioneer("Emil Leon Post").
computer_pioneer("Michael Oser Rabin").
computer_pioneer("Bertrand Russell").
computer_pioneer("Ken Thompson").
computer_pioneer("Alan Turing").
computer_pioneer("Joseph Weizenbaum").
computer_pioneer("Konrad Zuse").

Now we can query…

Let's ask who is computer_pioneer and logician


?-
computer_pioneer(Who), logician(Who).


=>
   Who = "Charles Babbage"
;  Who = "Kurt Gödel"
;  Who = "Amir Pnueli"
;  Who = "Emil Leon Post"
;  Who = "Michael Oser Rabin"
;  Who = "Bertrand Russell"
;  Who = "Alan Turing"
;  false.

To query for computer_pioneers or logicians, separate the terms with ";" instead of ","


?-
computer_pioneer(Who); logician(Who).

To query for logicians, who are not (primarily) known as computer_pioneer, we use a not, written as "\+"


?-
logician(Who), \+ computer_pioneer(Who).

More examples on this knowlede base can be found in this repository in src/scientists.pl.