From 017f1837b9cd412b7d50492706312164dee35e80 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 20 Apr 2018 10:40:13 +0200
Subject: [PATCH 1/5] Add interfaces.

---
 src/GeneratorInterface.php      | 21 +++++++++++++++++++++
 src/Generators/Combinations.php |  3 ++-
 src/Generators/Fibonacci.php    |  3 ++-
 src/Generators/FiniteGroup.php  |  3 ++-
 src/Generators/Perfect.php      |  3 ++-
 src/Generators/Permutations.php |  3 ++-
 src/Generators/Prime.php        |  3 ++-
 src/Generators/PrimeFactors.php |  3 ++-
 src/Generators/Product.php      |  3 ++-
 src/Generators/Shift.php        | 11 ++++++++++-
 src/IteratorInterface.php       |  7 +++++++
 src/Iterators/Combinations.php  |  3 ++-
 src/Iterators/Cycle.php         |  3 ++-
 src/Iterators/Fibonacci.php     |  3 ++-
 src/Iterators/FiniteGroup.php   |  3 ++-
 src/Iterators/NGrams.php        |  2 +-
 src/Iterators/Perfect.php       |  3 ++-
 src/Iterators/Prime.php         |  3 ++-
 src/Iterators/PrimeFactors.php  |  3 ++-
 src/Iterators/Product.php       |  3 ++-
 src/Iterators/Rotation.php      |  3 ++-
 src/Iterators/Shift.php         |  3 ++-
 22 files changed, 75 insertions(+), 20 deletions(-)
 create mode 100644 src/GeneratorInterface.php
 create mode 100644 src/IteratorInterface.php

diff --git a/src/GeneratorInterface.php b/src/GeneratorInterface.php
new file mode 100644
index 0000000..9fa62be
--- /dev/null
+++ b/src/GeneratorInterface.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace drupol\phpermutations;
+
+interface GeneratorInterface
+{
+    /**
+     * Get the generator.
+     *
+     * @return \Generator
+     *                    The generator
+     */
+    public function generator();
+
+    /**
+     * Convert the generator into an array.
+     *
+     * @return array
+     */
+    public function toArray();
+}
diff --git a/src/Generators/Combinations.php b/src/Generators/Combinations.php
index 066a42b..5d67257 100644
--- a/src/Generators/Combinations.php
+++ b/src/Generators/Combinations.php
@@ -2,6 +2,7 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Combinations as CombinationsIterator;
 
 /**
@@ -10,7 +11,7 @@
  *
  * @author Mark Wilson <mark@89allport.co.uk>
  */
-class Combinations extends CombinationsIterator
+class Combinations extends CombinationsIterator implements GeneratorInterface
 {
     /**
      * Alias of the get() method.
diff --git a/src/Generators/Fibonacci.php b/src/Generators/Fibonacci.php
index 0489225..a331c2d 100644
--- a/src/Generators/Fibonacci.php
+++ b/src/Generators/Fibonacci.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Fibonacci as FibonacciIterator;
 
 /**
  * Class Fibonacci.
  */
-class Fibonacci extends FibonacciIterator
+class Fibonacci extends FibonacciIterator implements GeneratorInterface
 {
     /**
      * The maximum value.
diff --git a/src/Generators/FiniteGroup.php b/src/Generators/FiniteGroup.php
index 6e6fba5..c9e9ce2 100644
--- a/src/Generators/FiniteGroup.php
+++ b/src/Generators/FiniteGroup.php
@@ -2,6 +2,7 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\FiniteGroup as FiniteGroupIterator;
 
 /**
@@ -9,7 +10,7 @@
  *
  * The finite group is an abelian finite cyclic group.
  */
-class FiniteGroup extends FiniteGroupIterator
+class FiniteGroup extends FiniteGroupIterator implements GeneratorInterface
 {
     /**
      * Alias of the get() method.
diff --git a/src/Generators/Perfect.php b/src/Generators/Perfect.php
index d87cfcb..0466764 100644
--- a/src/Generators/Perfect.php
+++ b/src/Generators/Perfect.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Perfect as PerfectIterator;
 
 /**
  * Class Perfect.
  */
-class Perfect extends PerfectIterator
+class Perfect extends PerfectIterator implements GeneratorInterface
 {
     /**
      * The maximum value.
diff --git a/src/Generators/Permutations.php b/src/Generators/Permutations.php
index 52f0a66..765cb0a 100644
--- a/src/Generators/Permutations.php
+++ b/src/Generators/Permutations.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Generators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\GeneratorInterface;
 
 /**
  * Class Permutations.
  */
-class Permutations extends Combinatorics
+class Permutations extends Combinatorics implements GeneratorInterface
 {
     /**
      * The combinations generator.
diff --git a/src/Generators/Prime.php b/src/Generators/Prime.php
index c038be1..162f9ad 100644
--- a/src/Generators/Prime.php
+++ b/src/Generators/Prime.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Prime as PrimeIterator;
 
 /**
  * Class Prime.
  */
-class Prime extends PrimeIterator
+class Prime extends PrimeIterator implements GeneratorInterface
 {
     /**
      * Alias of the get() method.
diff --git a/src/Generators/PrimeFactors.php b/src/Generators/PrimeFactors.php
index adb1cb1..3b34ff7 100644
--- a/src/Generators/PrimeFactors.php
+++ b/src/Generators/PrimeFactors.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\PrimeFactors as PrimeFactorsIterator;
 
 /**
  * Class PrimeFactors.
  */
-class PrimeFactors extends PrimeFactorsIterator
+class PrimeFactors extends PrimeFactorsIterator implements GeneratorInterface
 {
     /**
      * Alias of the get() method.
diff --git a/src/Generators/Product.php b/src/Generators/Product.php
index 4d846f5..80f524a 100644
--- a/src/Generators/Product.php
+++ b/src/Generators/Product.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Product as ProductIterator;
 
 /**
  * Class Product.
  */
-class Product extends ProductIterator
+class Product extends ProductIterator implements GeneratorInterface
 {
     /**
      * Get the generator.
diff --git a/src/Generators/Shift.php b/src/Generators/Shift.php
index 9d71579..3df3931 100644
--- a/src/Generators/Shift.php
+++ b/src/Generators/Shift.php
@@ -2,12 +2,13 @@
 
 namespace drupol\phpermutations\Generators;
 
+use drupol\phpermutations\GeneratorInterface;
 use drupol\phpermutations\Iterators\Shift as ShiftIterator;
 
 /**
  * Class Shift.
  */
-class Shift extends ShiftIterator
+class Shift extends ShiftIterator implements GeneratorInterface
 {
     /**
      * Get the generator.
@@ -20,6 +21,14 @@ public function generator()
         return $this->get();
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public function toArray()
+    {
+        return [];
+    }
+
     /**
      * Get the generator.
      *
diff --git a/src/IteratorInterface.php b/src/IteratorInterface.php
new file mode 100644
index 0000000..8dbe32a
--- /dev/null
+++ b/src/IteratorInterface.php
@@ -0,0 +1,7 @@
+<?php
+
+namespace drupol\phpermutations;
+
+interface IteratorInterface extends \Iterator
+{
+}
diff --git a/src/Iterators/Combinations.php b/src/Iterators/Combinations.php
index 86ee2f7..8790de4 100644
--- a/src/Iterators/Combinations.php
+++ b/src/Iterators/Combinations.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Combinations.
  */
-class Combinations extends Combinatorics implements \Iterator
+class Combinations extends Combinatorics implements IteratorInterface
 {
     /**
      * The values.
diff --git a/src/Iterators/Cycle.php b/src/Iterators/Cycle.php
index 9779741..f103479 100644
--- a/src/Iterators/Cycle.php
+++ b/src/Iterators/Cycle.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Cycle.
  */
-class Cycle extends Combinatorics implements \Iterator, \Countable
+class Cycle extends Combinatorics implements IteratorInterface
 {
     /**
      * The key.
diff --git a/src/Iterators/Fibonacci.php b/src/Iterators/Fibonacci.php
index fefff67..2b784ea 100644
--- a/src/Iterators/Fibonacci.php
+++ b/src/Iterators/Fibonacci.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Fibonacci.
  */
-class Fibonacci extends Combinatorics implements \Iterator, \Countable
+class Fibonacci extends Combinatorics implements IteratorInterface
 {
     /**
      * The maximum limit.
diff --git a/src/Iterators/FiniteGroup.php b/src/Iterators/FiniteGroup.php
index 85cc38c..01fc909 100644
--- a/src/Iterators/FiniteGroup.php
+++ b/src/Iterators/FiniteGroup.php
@@ -3,13 +3,14 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class FiniteGroup.
  *
  * The finite group is an abelian finite cyclic group.
  */
-class FiniteGroup extends Combinatorics implements \Iterator, \Countable
+class FiniteGroup extends Combinatorics implements IteratorInterface
 {
     /**
      * The group size.
diff --git a/src/Iterators/NGrams.php b/src/Iterators/NGrams.php
index 989b914..8a8c891 100644
--- a/src/Iterators/NGrams.php
+++ b/src/Iterators/NGrams.php
@@ -5,7 +5,7 @@
 /**
  * Class NGrams.
  */
-class NGrams extends Shift implements \Iterator, \Countable
+class NGrams extends Shift
 {
     /**
      * @var
diff --git a/src/Iterators/Perfect.php b/src/Iterators/Perfect.php
index 8ccfbbf..e0d10c4 100644
--- a/src/Iterators/Perfect.php
+++ b/src/Iterators/Perfect.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Perfect.
  */
-class Perfect extends Combinatorics implements \Iterator, \Countable
+class Perfect extends Combinatorics implements IteratorInterface
 {
     /**
      * The minimum limit.
diff --git a/src/Iterators/Prime.php b/src/Iterators/Prime.php
index 8be4edd..99fc64d 100644
--- a/src/Iterators/Prime.php
+++ b/src/Iterators/Prime.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Prime.
  */
-class Prime extends Combinatorics implements \Iterator, \Countable
+class Prime extends Combinatorics implements IteratorInterface
 {
     /**
      * The minimum limit.
diff --git a/src/Iterators/PrimeFactors.php b/src/Iterators/PrimeFactors.php
index 3f79e58..6131f75 100644
--- a/src/Iterators/PrimeFactors.php
+++ b/src/Iterators/PrimeFactors.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class PrimeFactors.
  */
-class PrimeFactors extends Combinatorics implements \Iterator, \Countable
+class PrimeFactors extends Combinatorics implements IteratorInterface
 {
     /**
      * The number.
diff --git a/src/Iterators/Product.php b/src/Iterators/Product.php
index 9226f4f..3c0f55a 100644
--- a/src/Iterators/Product.php
+++ b/src/Iterators/Product.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Product.
  */
-class Product extends Combinatorics implements \Iterator, \Countable
+class Product extends Combinatorics implements IteratorInterface
 {
     /**
      * The key.
diff --git a/src/Iterators/Rotation.php b/src/Iterators/Rotation.php
index 9064310..ea0c23d 100644
--- a/src/Iterators/Rotation.php
+++ b/src/Iterators/Rotation.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Rotation.
  */
-class Rotation extends Combinatorics implements \Iterator, \Countable
+class Rotation extends Combinatorics implements IteratorInterface
 {
     /**
      * The key.
diff --git a/src/Iterators/Shift.php b/src/Iterators/Shift.php
index 6a5b10c..d1cff11 100644
--- a/src/Iterators/Shift.php
+++ b/src/Iterators/Shift.php
@@ -3,11 +3,12 @@
 namespace drupol\phpermutations\Iterators;
 
 use drupol\phpermutations\Combinatorics;
+use drupol\phpermutations\IteratorInterface;
 
 /**
  * Class Shift.
  */
-class Shift extends Combinatorics implements \Iterator, \Countable
+class Shift extends Combinatorics implements IteratorInterface
 {
     /**
      * The key.

From 79185d35dfd123a7c8a0438359e192d8538195b8 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 20 Apr 2018 10:42:06 +0200
Subject: [PATCH 2/5] Update function documentation headers.

---
 src/Generators/Combinations.php | 10 ++--------
 src/Generators/Fibonacci.php    |  5 +----
 src/Generators/FiniteGroup.php  |  5 +----
 src/Generators/Perfect.php      | 12 +-----------
 src/Generators/Permutations.php | 12 ++----------
 src/Generators/Prime.php        |  5 +----
 src/Generators/PrimeFactors.php |  5 +----
 src/Generators/Product.php      |  5 +----
 src/Generators/Shift.php        |  5 +----
 9 files changed, 11 insertions(+), 53 deletions(-)

diff --git a/src/Generators/Combinations.php b/src/Generators/Combinations.php
index 5d67257..3d40e74 100644
--- a/src/Generators/Combinations.php
+++ b/src/Generators/Combinations.php
@@ -14,10 +14,7 @@
 class Combinations extends CombinationsIterator implements GeneratorInterface
 {
     /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The prime generator
+     * {@inheritdoc}
      */
     public function generator()
     {
@@ -25,10 +22,7 @@ public function generator()
     }
 
     /**
-     * Convert the generator into an array.
-     *
-     * @return array
-     *               The elements
+     * {@inheritdoc}
      */
     public function toArray()
     {
diff --git a/src/Generators/Fibonacci.php b/src/Generators/Fibonacci.php
index a331c2d..2686cf4 100644
--- a/src/Generators/Fibonacci.php
+++ b/src/Generators/Fibonacci.php
@@ -18,10 +18,7 @@ class Fibonacci extends FibonacciIterator implements GeneratorInterface
     protected $max;
 
     /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The prime generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/FiniteGroup.php b/src/Generators/FiniteGroup.php
index c9e9ce2..0a258aa 100644
--- a/src/Generators/FiniteGroup.php
+++ b/src/Generators/FiniteGroup.php
@@ -13,10 +13,7 @@
 class FiniteGroup extends FiniteGroupIterator implements GeneratorInterface
 {
     /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The finite group generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/Perfect.php b/src/Generators/Perfect.php
index 0466764..dc193dd 100644
--- a/src/Generators/Perfect.php
+++ b/src/Generators/Perfect.php
@@ -11,17 +11,7 @@
 class Perfect extends PerfectIterator implements GeneratorInterface
 {
     /**
-     * The maximum value.
-     *
-     * @var int
-     */
-    protected $max;
-
-    /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The prime generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/Permutations.php b/src/Generators/Permutations.php
index 765cb0a..519ebd5 100644
--- a/src/Generators/Permutations.php
+++ b/src/Generators/Permutations.php
@@ -32,12 +32,7 @@ public function __construct(array $dataset = [], $length = null)
     }
 
     /**
-     * Alias of the get() method.
-     *
-     * @codingStandardsIgnoreStart
-     *
-     * @return \Generator
-     * @codingStandardsIgnoreEnd
+     * {@inheritdoc}
      */
     public function generator()
     {
@@ -49,10 +44,7 @@ public function generator()
     }
 
     /**
-     * Convert the generator into an array.
-     *
-     * @return array
-     *               The elements
+     * {@inheritdoc}
      */
     public function toArray()
     {
diff --git a/src/Generators/Prime.php b/src/Generators/Prime.php
index 162f9ad..760715f 100644
--- a/src/Generators/Prime.php
+++ b/src/Generators/Prime.php
@@ -11,10 +11,7 @@
 class Prime extends PrimeIterator implements GeneratorInterface
 {
     /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The prime generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/PrimeFactors.php b/src/Generators/PrimeFactors.php
index 3b34ff7..46d33db 100644
--- a/src/Generators/PrimeFactors.php
+++ b/src/Generators/PrimeFactors.php
@@ -11,10 +11,7 @@
 class PrimeFactors extends PrimeFactorsIterator implements GeneratorInterface
 {
     /**
-     * Alias of the get() method.
-     *
-     * @return \Generator
-     *                    The prime factors generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/Product.php b/src/Generators/Product.php
index 80f524a..b1c7e57 100644
--- a/src/Generators/Product.php
+++ b/src/Generators/Product.php
@@ -11,10 +11,7 @@
 class Product extends ProductIterator implements GeneratorInterface
 {
     /**
-     * Get the generator.
-     *
-     * @return \Generator
-     *                    The generator
+     * {@inheritdoc}
      */
     public function generator()
     {
diff --git a/src/Generators/Shift.php b/src/Generators/Shift.php
index 3df3931..1c9aee9 100644
--- a/src/Generators/Shift.php
+++ b/src/Generators/Shift.php
@@ -11,10 +11,7 @@
 class Shift extends ShiftIterator implements GeneratorInterface
 {
     /**
-     * Get the generator.
-     *
-     * @return \Generator
-     *                    The generator
+     * {@inheritdoc}
      */
     public function generator()
     {

From d4647c9672a8d5366bb60d0cb8101eaaaa316a14 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 20 Apr 2018 10:44:47 +0200
Subject: [PATCH 3/5] Move methods count() and toArray() into the parent class.

---
 src/Combinatorics.php          | 36 ++++++++++++++++++++++++++++++++++
 src/Generators/Fibonacci.php   |  7 -------
 src/Iterators/Combinations.php | 25 -----------------------
 src/Iterators/Cycle.php        |  8 --------
 src/Iterators/Fibonacci.php    | 33 -------------------------------
 src/Iterators/FiniteGroup.php  | 25 -----------------------
 src/Iterators/Perfect.php      | 36 ----------------------------------
 src/Iterators/Prime.php        | 36 ----------------------------------
 src/Iterators/PrimeFactors.php | 25 -----------------------
 src/Iterators/Product.php      |  8 --------
 src/Iterators/Rotation.php     |  8 --------
 src/Iterators/Shift.php        |  8 --------
 12 files changed, 36 insertions(+), 219 deletions(-)

diff --git a/src/Combinatorics.php b/src/Combinatorics.php
index 1ab62e8..7414beb 100644
--- a/src/Combinatorics.php
+++ b/src/Combinatorics.php
@@ -96,6 +96,42 @@ public function getDataset()
         return $this->dataset;
     }
 
+    /**
+     * Count elements of an object.
+     *
+     * @return int
+     *             The number of element
+     */
+    public function count()
+    {
+        return count($this->toArray());
+    }
+
+    /**
+     * Convert the iterator into an array.
+     *
+     * @return array
+     *               The elements
+     */
+    public function toArray()
+    {
+        $data = [];
+
+        for ($this->rewind(); $this->valid(); $this->next()) {
+            $data[] = $this->current();
+        }
+
+        return $data;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function key()
+    {
+        return $this->key;
+    }
+
     /**
      * Compute the factorial of an integer.
      *
diff --git a/src/Generators/Fibonacci.php b/src/Generators/Fibonacci.php
index 2686cf4..2dba1fb 100644
--- a/src/Generators/Fibonacci.php
+++ b/src/Generators/Fibonacci.php
@@ -10,13 +10,6 @@
  */
 class Fibonacci extends FibonacciIterator implements GeneratorInterface
 {
-    /**
-     * The maximum value.
-     *
-     * @var int
-     */
-    protected $max;
-
     /**
      * {@inheritdoc}
      */
diff --git a/src/Iterators/Combinations.php b/src/Iterators/Combinations.php
index 8790de4..45fb248 100644
--- a/src/Iterators/Combinations.php
+++ b/src/Iterators/Combinations.php
@@ -38,14 +38,6 @@ public function __construct(array $dataset = [], $length = null)
         $this->rewind();
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -88,23 +80,6 @@ public function valid()
         return $this->key >= 0;
     }
 
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * {@inheritdoc}
      */
diff --git a/src/Iterators/Cycle.php b/src/Iterators/Cycle.php
index f103479..cb9f93b 100644
--- a/src/Iterators/Cycle.php
+++ b/src/Iterators/Cycle.php
@@ -17,14 +17,6 @@ class Cycle extends Combinatorics implements IteratorInterface
      */
     protected $key = 0;
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
diff --git a/src/Iterators/Fibonacci.php b/src/Iterators/Fibonacci.php
index 2b784ea..14c2559 100644
--- a/src/Iterators/Fibonacci.php
+++ b/src/Iterators/Fibonacci.php
@@ -54,14 +54,6 @@ public function current()
         return $this->current;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -89,31 +81,6 @@ public function valid()
         return $this->current < $this->getMaxLimit();
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function count()
-    {
-        return count($this->toArray());
-    }
-
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * Set the maximum limit.
      *
diff --git a/src/Iterators/FiniteGroup.php b/src/Iterators/FiniteGroup.php
index 01fc909..442bbd7 100644
--- a/src/Iterators/FiniteGroup.php
+++ b/src/Iterators/FiniteGroup.php
@@ -58,14 +58,6 @@ public function next()
         next($this->group);
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -93,23 +85,6 @@ public function count()
         return count($this->group);
     }
 
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * Set the group size.
      *
diff --git a/src/Iterators/Perfect.php b/src/Iterators/Perfect.php
index e0d10c4..a3acc6c 100644
--- a/src/Iterators/Perfect.php
+++ b/src/Iterators/Perfect.php
@@ -64,14 +64,6 @@ public function next()
         ++$this->key;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -88,34 +80,6 @@ public function rewind()
         $this->key = $this->getMinLimit();
     }
 
-    /**
-     * Count elements of an object.
-     *
-     * @return int
-     *             The number of element
-     */
-    public function count()
-    {
-        return count($this->toArray());
-    }
-
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * Set the maximum limit.
      *
diff --git a/src/Iterators/Prime.php b/src/Iterators/Prime.php
index 99fc64d..2dce498 100644
--- a/src/Iterators/Prime.php
+++ b/src/Iterators/Prime.php
@@ -64,14 +64,6 @@ public function next()
         ++$this->key;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -88,34 +80,6 @@ public function rewind()
         $this->key = $this->getMinLimit();
     }
 
-    /**
-     * Count elements of an object.
-     *
-     * @return int
-     *             The number of element
-     */
-    public function count()
-    {
-        return count($this->toArray());
-    }
-
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * Set the maximum limit.
      *
diff --git a/src/Iterators/PrimeFactors.php b/src/Iterators/PrimeFactors.php
index 6131f75..8ec2aa0 100644
--- a/src/Iterators/PrimeFactors.php
+++ b/src/Iterators/PrimeFactors.php
@@ -48,14 +48,6 @@ public function next()
         next($this->factors);
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -83,23 +75,6 @@ public function count()
         return count($this->factors);
     }
 
-    /**
-     * Convert the iterator into an array.
-     *
-     * @return array
-     *               The elements
-     */
-    public function toArray()
-    {
-        $data = [];
-
-        for ($this->rewind(); $this->valid(); $this->next()) {
-            $data[] = $this->current();
-        }
-
-        return $data;
-    }
-
     /**
      * Set the number.
      *
diff --git a/src/Iterators/Product.php b/src/Iterators/Product.php
index 3c0f55a..419e331 100644
--- a/src/Iterators/Product.php
+++ b/src/Iterators/Product.php
@@ -77,14 +77,6 @@ public function next()
         ++$this->key;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
diff --git a/src/Iterators/Rotation.php b/src/Iterators/Rotation.php
index ea0c23d..80e804a 100644
--- a/src/Iterators/Rotation.php
+++ b/src/Iterators/Rotation.php
@@ -36,14 +36,6 @@ public function __construct(array $dataset = [])
         $this->rotation = $this->getDataset();
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */
diff --git a/src/Iterators/Shift.php b/src/Iterators/Shift.php
index d1cff11..5433d99 100644
--- a/src/Iterators/Shift.php
+++ b/src/Iterators/Shift.php
@@ -49,14 +49,6 @@ public function setLength($length = null)
         return $this;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function key()
-    {
-        return $this->key;
-    }
-
     /**
      * {@inheritdoc}
      */

From 35f451fa92e926cafe8267ce30316e2410719464 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 20 Apr 2018 10:45:42 +0200
Subject: [PATCH 4/5] Small code cleanup.

---
 src/Combinatorics.php          | 2 +-
 src/Iterators/Combinations.php | 3 +++
 src/Iterators/Fibonacci.php    | 3 ++-
 src/Iterators/FiniteGroup.php  | 4 ++--
 src/Iterators/Perfect.php      | 3 ++-
 src/Iterators/Prime.php        | 5 +++--
 src/Iterators/PrimeFactors.php | 6 ++----
 src/Iterators/Rotation.php     | 2 +-
 src/Iterators/Shift.php        | 8 ++++----
 9 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/Combinatorics.php b/src/Combinatorics.php
index 7414beb..aad06ff 100644
--- a/src/Combinatorics.php
+++ b/src/Combinatorics.php
@@ -53,7 +53,7 @@ public function __construct(array $dataset = [], $length = null)
      */
     public function setLength($length = null)
     {
-        $length = is_null($length) ? $this->datasetCount : $length;
+        $length = (null === $length) ? $this->datasetCount : $length;
         $this->length = ($length > $this->datasetCount) ? $this->datasetCount : $length;
 
         return $this;
diff --git a/src/Iterators/Combinations.php b/src/Iterators/Combinations.php
index 45fb248..2c8274d 100644
--- a/src/Iterators/Combinations.php
+++ b/src/Iterators/Combinations.php
@@ -44,6 +44,7 @@ public function __construct(array $dataset = [], $length = null)
     public function current()
     {
         $r = [];
+
         for ($i = 0; $i < $this->length; ++$i) {
             $r[] = $this->dataset[$this->c[$i]];
         }
@@ -101,9 +102,11 @@ protected function nextHelper()
         while ($i >= 0 && $this->c[$i] === $this->datasetCount - $this->length + $i) {
             --$i;
         }
+
         if ($i < 0) {
             return false;
         }
+
         ++$this->c[$i];
         while ($i++ < $this->length - 1) {
             $this->c[$i] = $this->c[$i - 1] + 1;
diff --git a/src/Iterators/Fibonacci.php b/src/Iterators/Fibonacci.php
index 14c2559..cab3213 100644
--- a/src/Iterators/Fibonacci.php
+++ b/src/Iterators/Fibonacci.php
@@ -44,6 +44,7 @@ class Fibonacci extends Combinatorics implements IteratorInterface
     public function __construct()
     {
         $this->setMaxLimit(PHP_INT_MAX);
+        parent::__construct([], null);
     }
 
     /**
@@ -100,6 +101,6 @@ public function setMaxLimit($max)
      */
     public function getMaxLimit()
     {
-        return intval($this->max);
+        return (int) $this->max;
     }
 }
diff --git a/src/Iterators/FiniteGroup.php b/src/Iterators/FiniteGroup.php
index 442bbd7..f6c404d 100644
--- a/src/Iterators/FiniteGroup.php
+++ b/src/Iterators/FiniteGroup.php
@@ -105,7 +105,7 @@ public function setSize($size)
      */
     public function getSize()
     {
-        return intval($this->size);
+        return (int) $this->size;
     }
 
     /**
@@ -122,7 +122,7 @@ public function order($generator)
         $result = [];
 
         foreach (range(1, $this->getSize() - 1) as $number) {
-            $value = pow($generator, $number) % $this->getSize();
+            $value = ($generator ** $number) % $this->getSize();
             $result[$value] = $value;
         }
 
diff --git a/src/Iterators/Perfect.php b/src/Iterators/Perfect.php
index a3acc6c..650fda3 100644
--- a/src/Iterators/Perfect.php
+++ b/src/Iterators/Perfect.php
@@ -38,6 +38,7 @@ public function __construct()
     {
         $this->setMaxLimit(PHP_INT_MAX);
         $this->setMinLimit(2);
+        parent::__construct([], null);
     }
 
     /**
@@ -99,7 +100,7 @@ public function setMaxLimit($max)
      */
     public function getMaxLimit()
     {
-        return intval($this->max);
+        return (int) $this->max;
     }
 
     /**
diff --git a/src/Iterators/Prime.php b/src/Iterators/Prime.php
index 2dce498..a5089c7 100644
--- a/src/Iterators/Prime.php
+++ b/src/Iterators/Prime.php
@@ -38,6 +38,7 @@ public function __construct()
     {
         $this->setMaxLimit(PHP_INT_MAX);
         $this->setMinLimit(0);
+        parent::__construct([], null);
     }
 
     /**
@@ -99,7 +100,7 @@ public function setMaxLimit($max)
      */
     public function getMaxLimit()
     {
-        return intval($this->max);
+        return (int) $this->max;
     }
 
     /**
@@ -121,7 +122,7 @@ public function setMinLimit($min)
      */
     public function getMinLimit()
     {
-        return $this->min <= 2 ? 2 : intval($this->min);
+        return $this->min <= 2 ? 2 : (int) $this->min;
     }
 
     /**
diff --git a/src/Iterators/PrimeFactors.php b/src/Iterators/PrimeFactors.php
index 8ec2aa0..fe73114 100644
--- a/src/Iterators/PrimeFactors.php
+++ b/src/Iterators/PrimeFactors.php
@@ -95,7 +95,7 @@ public function setNumber($number)
      */
     public function getNumber()
     {
-        return intval($this->number);
+        return (int) $this->number;
     }
 
     /**
@@ -108,9 +108,7 @@ public function getNumber()
      */
     private function getFactors($number)
     {
-        if ($number <= 0) {
-            $factors = [];
-        }
+        $factors = [];
 
         for ($i = 2; $i <= $number / $i; ++$i) {
             while (0 === $number % $i) {
diff --git a/src/Iterators/Rotation.php b/src/Iterators/Rotation.php
index 80e804a..f355536 100644
--- a/src/Iterators/Rotation.php
+++ b/src/Iterators/Rotation.php
@@ -52,7 +52,7 @@ public function current()
      */
     public function next($offset = 1)
     {
-        $offset = is_null($offset) ? 1 : $offset % $this->count();
+        $offset = (null === $offset) ? 1 : $offset % $this->count();
         $this->rotation = array_merge(array_slice($this->rotation, $offset), array_slice($this->rotation, 0, $offset));
     }
 
diff --git a/src/Iterators/Shift.php b/src/Iterators/Shift.php
index 5433d99..b9a9d8d 100644
--- a/src/Iterators/Shift.php
+++ b/src/Iterators/Shift.php
@@ -43,7 +43,7 @@ public function __construct(array $dataset = [], $length = 1)
      */
     public function setLength($length = null)
     {
-        $length = is_null($length) ? $this->datasetCount : $length;
+        $length = (null === $length) ? $this->datasetCount : $length;
         $this->length = (abs($length) > $this->datasetCount) ? $this->datasetCount : $length;
 
         return $this;
@@ -107,8 +107,8 @@ protected function doShift($length = 1)
         }
 
         $this->current = array_merge(
-        array_slice($this->current, $parameters[0]['start'], $parameters[0]['end']),
-        array_slice($this->current, $parameters[1]['start'], $parameters[1]['end'])
-      );
+            array_slice($this->current, $parameters[0]['start'], $parameters[0]['end']),
+            array_slice($this->current, $parameters[1]['start'], $parameters[1]['end'])
+        );
     }
 }

From 280927644bd92053058cf5c01cf3e72086bf4248 Mon Sep 17 00:00:00 2001
From: Pol Dellaiera <pol.dellaiera@protonmail.com>
Date: Fri, 20 Apr 2018 10:46:02 +0200
Subject: [PATCH 5/5] Add the NGrams generator and its tests.

---
 src/Generators/NGrams.php          | 45 ++++++++++++++++++++++++++++++
 tests/src/Iterators/NgramsTest.php | 10 +++----
 2 files changed, 50 insertions(+), 5 deletions(-)
 create mode 100644 src/Generators/NGrams.php

diff --git a/src/Generators/NGrams.php b/src/Generators/NGrams.php
new file mode 100644
index 0000000..d088154
--- /dev/null
+++ b/src/Generators/NGrams.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace drupol\phpermutations\Generators;
+
+use drupol\phpermutations\GeneratorInterface;
+use drupol\phpermutations\Iterators\NGrams as NGramsIterator;
+
+/**
+ * Class NGrams.
+ */
+class NGrams extends NGramsIterator implements GeneratorInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function generator()
+    {
+        return $this->get();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function toArray()
+    {
+        return [];
+    }
+
+    /**
+     * Get the generator.
+     *
+     * @codingStandardsIgnoreStart
+     *
+     * @return \Generator
+     *                    The generator
+     * @codingStandardsIgnoreEnd
+     */
+    protected function get()
+    {
+        while (true) {
+            $this->next();
+            yield $this->current();
+        }
+    }
+}
diff --git a/tests/src/Iterators/NgramsTest.php b/tests/src/Iterators/NgramsTest.php
index 534d148..fe81c3b 100644
--- a/tests/src/Iterators/NgramsTest.php
+++ b/tests/src/Iterators/NgramsTest.php
@@ -25,14 +25,14 @@ class NgramsTest extends AbstractTest
      */
     public function testNgrams($input, $expected)
     {
-        $shift = new NGrams($input['dataset'], $input['length']);
+        $ngrams = new NGrams($input['dataset'], $input['length']);
 
         for ($i = 0; $i < $input['turn']; ++$i) {
-            $shift->next();
+            $ngrams->next();
         }
-        $this->assertEquals($expected['current'], $shift->current());
+        $this->assertEquals($expected['current'], $ngrams->current());
 
-        $this->assertEquals($input['dataset'], $shift->getDataset());
-        $this->assertEquals($expected['count'], $shift->count());
+        $this->assertEquals($input['dataset'], $ngrams->getDataset());
+        $this->assertEquals($expected['count'], $ngrams->count());
     }
 }