Point operator (programming languages)

The dot operator is an access operator that is part of many programming languages ​​such as Pascal , C or Java . It is used to access elements of classes or data structures . Such accesses take place through calls of the form "Class.Method" or "Class.Attribute", which, for example, enable access to methods or attributes of a class.

The dot operator is very similar to the array access operator. With the dot operator, an identifier is used as a property, while the array access operator evaluates the content of a name and then accesses the value of this named property.

example

The following example for the use of the point operator is written in the Java programming language:

  public class Auto {
    public int kilometerstand;
    public void losfahren() {
      System.out.println("Das Auto fährt jetzt.");
    }
  }
  public static void main(String[] args) {
    Auto vw_kaefer = new Auto();
    vw_kaefer.kilometerstand = 200.345;
    System.out.println("Der Kilometerstand beträgt " + vw_kaefer.kilometerstand + " km.");
    vw_kaefer.losfahren();
  }

In the upper part, a class is defined with the attribute kilometerstandand the method losfahren. In the main class (below) an instance of Autowith the name is first vw_kaefercreated. The second statement assigns a value to the attribute kilometerstandof vw_kaefer. This is queried and output in the next line. Finally, the “start driving” method is vw_kaefercalled.

Different meanings

The operator has does not exist in any programming language in which it, the same semantics (meaning), for example, the dot operator in has PHP a different semantics, here it is used to string ( character strings ) (to adhere to each other) to concatenate. In PHP, the code would have

 $a = "Hallo" . " " . "Welt.";

the effect of getting $athe value "Hallo Welt."assigned. Instead of the point operator from the “C C ++ Java” world, the operator " ->" exists in PHP .

Based on the mathematical notation, the operator . from Haskell's standard library the meaning of the functional composition .