Comparable

Reference

Definition

Namespace: Quant\Core\Contract

Comparable implements a total order for objects.

interface Comparable

Example

#[Getter]
class Money implements Comparable {

    use AccessorTrait;
    
    public function __construct(
        private int $amount,
        private int $cents
    ) {
    } 

    public function compareTo(Comparable $b): array
    {
        if (!($b instanceof Money)) {
            return false;
        }
        
        $aAmount = $this->getAmount();
        $bAmount = $b->getAmount();
        
        $aCents = $this->getCents();
        $bCents = $b->getCents();
        
        
        $c = ($aAmount === $bAmount ? 0 : ($aAmount < $bAmount ? -1 : 1));
        
        return $c !== 0 ?  $c : ($aCents < $bCents ? -1 : ($aCents > $bCents ? 1 : 0));
    }

}

Remarks

This interface implements a total order on T for objects of T, with T being a subtype of Comparable. It provides a method compareTo whose implementation must, for all $a, b \in T$, conform to

• $(a \in T) \space \lt \space (b \in T) :\iff a$->$compareTo(b) = -1$
• $(a \in T) \space = \space (b \in T) :\iff a$->$compareTo(b) = 0$
• $(a \in T) \space \gt \space (b \in T) :\iff a$->$compareTo(b) = 1$

In this regard, compareTo is

• reflexive: $a->compareTo($a) $=0$
• antisymmetric: $a->compareTo($b) $\le 0$ $\land$ $b->compareTo($a) $\le 0$ $\implies$ $a->compareTo($b) $=0$
• transitive: $a->compareTo($b) $\le 0$ $\land$ $b->compareTo($c) $\le 0$ $\implies$ $a->compareTo($c) $\le 0$
• total: $a->compareTo($b) $\in \{-1, 0, 1\} \lor$ $b->compareTo($a) $\in \{-1, 0, 1\}$

The order should be consistent with objects implementing Equatable: If $a->equals($b) $\implies$ $a->compareTo($b) $=0$

Methods

Name	Description
compareTo(Comparable $obj): int	Returns -1 if $this is considered to be less than $obj, 0 if it's equal and 1 if $this is considered to be greater than $obj