Name

SPVM::Comparator - Interface Type for Object Comparation Callback

Usage

  use Comparator;
  use Point;
  
  my $comparator = (Comparator)method : int ($object1 : object, $object2 : object); {
    my $point1 = (Point)$object1;
    my $point2 = (Point)$object2;
    
    if ($point1->x > $point2->x) {
      return 1;
    }
    elsif ($point1->x < $point2->x) {
      return -1;
    }
    else {
      return 0;
    }
  };
  
  my $point1 = Point->new(1, 2);
  my $point2 = Point->new(5, 6);
  my $result = $comparator->($point1, $point2);

Description

Comparator is the interface type for the object comparation callback.

Interface Methods

required method : int ($object1 : object, $object2 : object);

This method must receive two objects and return the following value.

If the first argument is greater than the second argument, returns 1. If the first argument is lower than the second argument, returns -1. If the first argument is equal to the second argument, returns 0.

Class Methods

default_comparator

static method default_comparator : Comparator ();

Returns a default comparator.

The implementation of the default comparator is

  method : int ($object1 : Comparable, $object2 : Comparable) {
      
      my $cmp = 0;
      if ($object1 && $object2) {
        $cmp = $object1->cmp($object1, $object2);
      }
      elsif ($object1) {
        $cmp = 1;
      }
      elsif ($object2 ) {
        $cmp = -1;
      }
      
      return $cmp;
    }
    
    return $default_comparator;
  }

If $object1 and $object2 are defined, the comparison is perfermed by Comparable#cmp method in the class of $object1, and returns its return value.

If only $object1 is defined, returns 1.

If only $object2 is defined, returns -1.

If both $object1 and $object2 are not defined, returns 0.

Copyright & License

Copyright (c) 2023 Yuki Kimoto

MIT License