Remove one of the interfaces

src/Interfaces/StandardPipeline.php

@@ -22,14 +22,14 @@
 /**
  * Interface definitions for the standard pipeline.
  */
-interface StandardPipeline extends PrincipalPipeline
+interface StandardPipeline extends \IteratorAggregate, \Countable
 {
     /**
-     * {@inheritdoc}
+     * Takes a callback that for each input value may return one or yield many. Also takes an initial generator, where it must not require any arguments.
      *
      * With no callback is a no-op (can safely take a null).
      *
-     * @param ?callable $func {@inheritdoc}
+     * @param ?callable $func a callback must either return a value or yield values (return a generator)
      *
      * @return $this
      */
@@ -45,7 +45,7 @@ public function map(?callable $func = null);
     public function unpack(?callable $func = null);
 
     /**
-     * {@inheritdoc}
+     * Removes elements unless a callback returns true.
      *
      * With no callback drops all null and false values (not unlike array_filter does by default).
      *
@@ -66,19 +66,27 @@ public function filter(?callable $func = null);
     public function reduce(?callable $func = null, $initial = null);
 
     /**
-     * {@inheritdoc}
+     * Reduces input values to a single value.
      *
      * Defaults to summation.
      *
-     * @param ?mixed    $initial {@inheritdoc}
-     * @param ?callable $func    {@inheritdoc}
+     * @param mixed     $initial initial value for a $carry
+     * @param ?callable $func    function (mixed $carry, mixed $item) { must return updated $carry }
      *
      * @return ?mixed
      */
     public function fold($initial, ?callable $func = null);
 
     /**
-     * {@inheritdoc}
+     * Performs a lazy zip operation on iterables, not unlike that of
+     * array_map with first argument set to null. Also known as transposition.
+     *
+     * @return $this
+     */
+    public function zip(iterable ...$inputs);
+
+    /**
+     * By default returns all values regardless of keys used, discarding all keys in the process. Has an option to keep the keys.
      */
-    public function toArray(): array;
+    public function toArray(bool $useKeys = false): array;
 }

src/Principal.php

@@ -24,7 +24,7 @@
  *
  * @internal
  */
-abstract class Principal implements Interfaces\PrincipalPipeline
+abstract class Principal implements \IteratorAggregate, \Countable
 {
     /**
      * Pre-primed pipeline. This is not a full `iterable` per se because we exclude IteratorAggregate before assigning a value.
@@ -50,13 +50,9 @@ final public function __construct(iterable $input = null)
     }
 
     /**
-     * {@inheritdoc}
-     *
-     * @param callable $func {@inheritdoc}
-     *
      * @return $this
      */
-    public function map(callable $func)
+    protected function map(callable $func)
     {
         // That's the standard case for any next stages
         if (\is_iterable($this->pipeline)) {
@@ -105,13 +101,9 @@ private static function apply(iterable $previous, callable $func): iterable
     }
 
     /**
-     * {@inheritdoc}
-     *
-     * @param callable $func {@inheritdoc}
-     *
      * @return $this
      */
-    public function filter(callable $func)
+    protected function filter(callable $func)
     {
         if (null === $this->pipeline) {
             // No-op: null.
@@ -139,9 +131,6 @@ public function filter(callable $func)
         return $this;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getIterator(): \Traversable
     {
         if ($this->pipeline instanceof \Traversable) {
@@ -155,9 +144,6 @@ public function getIterator(): \Traversable
         return new \EmptyIterator();
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function toArray(bool $useKeys = false): array
     {
         if (null === $this->pipeline) {
@@ -205,14 +191,11 @@ public function count(): int
     }
 
     /**
-     * {@inheritdoc}
-     *
-     * @param mixed    $initial {@inheritdoc}
-     * @param callable $func    {@inheritdoc}
+     * @param mixed $initial
      *
      * @return ?mixed
      */
-    public function fold($initial, callable $func)
+    protected function fold($initial, callable $func)
     {
         if (\is_array($this->pipeline)) {
             return \array_reduce($this->pipeline, $func, $initial);
@@ -226,7 +209,7 @@ public function fold($initial, callable $func)
     }
 
     /**
-     * {@inheritdoc}
+     * @return $this
      */
     public function zip(iterable ...$inputs)
     {

tests/InterfaceTest.php

@@ -20,7 +20,6 @@
 namespace Tests\Pipeline;
 
 use PHPUnit\Framework\TestCase;
-use Pipeline\Interfaces\PrincipalPipeline;
 use Pipeline\Interfaces\StandardPipeline;
 use Pipeline\Standard;
 
@@ -44,16 +43,4 @@ public function testStandardInterface(): void
 
         $this->assertInstanceOf(StandardPipeline::class, $pipeline);
     }
-
-    private function takesPrincipalInterface(PrincipalPipeline $pipeline)
-    {
-        return $pipeline;
-    }
-
-    public function testPrincipalInterface(): void
-    {
-        $pipeline = new Standard();
-
-        $this->assertInstanceOf(PrincipalPipeline::class, $this->takesPrincipalInterface($pipeline));
-    }
 }