add negate alias for not method of predicate

src/Predicate.php

@@ -15,6 +15,7 @@ interface Predicate
     public function __invoke(...$args): bool;
 
     public function not(): Predicate;
+    public function negate(): Predicate; // should ALWAYS be alias for not
 
     public function and(...$predicate): Predicate;
     public function or(...$predicate): Predicate;

src/Predicate/NegatedPredicate.php

@@ -10,9 +10,10 @@
 namespace Kadet\Functional\Predicate;
 
 
+use Kadet\Functional\Decorator;
 use Kadet\Functional\Predicate;
 
-class NegatedPredicate extends AbstractPredicate
+class NegatedPredicate extends AbstractPredicate implements Decorator
 {
     /**
      * Predicate to be negated.
@@ -35,4 +36,9 @@ class NegatedPredicate extends AbstractPredicate
     {
         return !($this->negated)(...$args);
     }
+
+    public function getDecorated()
+    {
+        $this->negated;
+    }
 }