Introduction to Conjunctions & Disjunctions in Prolog Programming Language

Hello, fellow Prolog enthusiasts! In this blog post,

I will introduce you to the concepts of conjunctions and disjunctions in Prolog, and show you how they can be used to write powerful and elegant logic programs. Conjunctions and disjunctions are two of the most basic and important operators in Prolog, and they allow you to express complex logical relationships between facts and rules. Let’s dive in!

Conjunctions & Disjunctions in Prolog Language

In Prolog, conjunctions and disjunctions are logical connectives used to combine multiple conditions or goals in rules and queries. These connectives allow you to express complex relationships between conditions and make decisions based on multiple criteria. Here’s how conjunctions (logical AND) and disjunctions (logical OR) work in Prolog:

Conjunction (Logical AND) in Prolog Language:

In Prolog, conjunction is represented by a comma (,). When multiple conditions are connected by a comma, all conditions must be satisfied for the conjunction to be true. It’s similar to saying “A AND B” must both be true for the overall condition to be true.

% Example of conjunction (AND)
happy(john), sunny_day.

In this example, the query checks if both “john” is happy and it’s a sunny day for the overall condition to be true.

Disjunction (Logical OR) in Prolog Language:

In Prolog, disjunction is represented by a semicolon (;). When multiple conditions are connected by a semicolon, at least one of the conditions must be satisfied for the disjunction to be true. It’s similar to saying “A OR B” where either “A” or “B” being true makes the overall condition true.

% Example of disjunction (OR)
likes(john, ice_cream) ; likes(john, pizza).

In this example, the query checks if John likes either ice cream or pizza. If he likes at least one of them, the overall condition is true.

Combining Conjunctions and Disjunctions in Prolog Language:
You can also combine conjunctions and disjunctions to create more complex conditions. Parentheses can be used to control the order of evaluation, just like in mathematical expressions.

% Example of combining conjunction and disjunction
happy(john) ; (sunny_day, not(busy(john))).

In this example, the condition is true if John is happy OR it’s a sunny day and John is not busy. The parentheses ensure that the sunny day and not busy conditions are evaluated together before being combined with the happy condition using disjunction.

Negation (Logical NOT) in Prolog Language:
In addition to conjunctions and disjunctions, you can use negation to express logical NOT using the not/1 predicate. For example, not(sunny_day) means “it’s not a sunny day.”

% Example of negation (NOT)
rainy_day :- not(sunny_day).