What is the difference between Java functions and Prolog functions?

Java functions are declared in public, parameters are passed by value, and there is strong type checking; Prolog functions are declared in capital letters, and parameters are passed by value and reference using logical variables, without type checking.

The difference between Java functions and Prolog functions

Java and Prolog are two completely different programming languages. There are also obvious differences.

Declaration

In Java, functions are usually declared using the public keyword, followed by the function name and a parameter list in parentheses:

public double calculateArea(double radius) {
    // 计算圆的面积
}

In Prolog, functions are called predicates, declared using uppercase letters:

calculateArea(Radius, Area) :-
    Area = pi * Radius * Radius.

call

In Java, a function can be called by its name and its Parameters are called:

double area = calculateArea(10.0);

In Prolog, predicates are usually called using question marks (?), and the parameters are specified in order within parentheses:

calculateArea(10.0, Area).

Parameter passing

Java uses parameters passed by value, which means a copy of the parameters is passed to the function. Modifying parameters within a function does not affect the original value.

double radius = 10.0;
calculateArea(radius);
// radius 仍然为 10.0

Prolog uses logical variables for parameter passing. This means that parameters can be inputs, outputs, or both.

calculateArea(Radius, 100.0).
Radius = 11.283...

Type checking

Java has strong type checking, which means that the types of parameters and return values ​​must be specified in the function declaration.

public double calculateArea(double radius) {
    return radius * radius;
}

Prolog is a typeless language, which means that the types of parameters and return values ​​are determined at runtime.

Practical Case

The following example uses Java and Prolog to calculate the area of ​​a circle:

Java

public class Circle {

    public static double calculateArea(double radius) {
        return Math.PI * radius * radius;
    }

    public static void main(String[] args) {
        double radius = 10.0;
        double area = calculateArea(radius);
        System.out.println("Area: " + area);
    }
}

Prolog

calculateArea(Radius, Area) :-
    Area = pi * Radius * Radius.

main :-
    Radius = 10.0,
    calculateArea(Radius, Area),
    format("Area: ~f~n", [Area]).

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