Predicate Logic : Introduction

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General Idea

There are functions of N variables that return a boolean values. The types of the variables can differ. The functions are called predicates.

An example:

Eats(the_one_who_digests,food_item)

As the predicates are functions that return boolean values, they can be combined with each-other by the means of propositional logic. An example:

Eats(the_one_who_digests,food_item) AND GoesToHell(politician)

A function that is constructed by combining predicates by the means of propositional logic is itself a predicate, because it takes in N variables and always returns a boolean value. An example:

JustAnotherPredicate(the_one_who_digests,food_item,politician):=
:=Eats(the_one_who_digests,food_item) AND GoesToHell(politician)