add Layer, Input and Bias for neutal network

src/Phpml/Exception/InvalidArgumentException.php

@@ -73,4 +73,12 @@ class InvalidArgumentException extends \Exception
     {
         return new self(sprintf('Can\'t find %s language for StopWords', $language));
     }
+
+    /**
+     * @return InvalidArgumentException
+     */
+    public static function invalidLayerNodeClass()
+    {
+        return new self('Layer node class must implement Node interface');
+    }
 }

src/Phpml/NeuralNetwork/Layer.php

@@ -0,0 +1,49 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace Phpml\NeuralNetwork;
+
+use Phpml\Exception\InvalidArgumentException;
+use Phpml\NeuralNetwork\Node\Neuron;
+
+class Layer
+{
+    /**
+     * @var Node[]
+     */
+    private $nodes = [];
+
+    /**
+     * @param int    $nodesNumber
+     * @param string $nodeClass
+     *
+     * @throws InvalidArgumentException
+     */
+    public function __construct(int $nodesNumber = 0, string $nodeClass = Neuron::class)
+    {
+        if (!in_array(Node::class, class_implements($nodeClass))) {
+            throw InvalidArgumentException::invalidLayerNodeClass();
+        }
+
+        for ($i = 0; $i < $nodesNumber; ++$i) {
+            $this->nodes[] = new $nodeClass();
+        }
+    }
+
+    /**
+     * @param Node $node
+     */
+    public function addNode(Node $node)
+    {
+        $this->nodes[] = $node;
+    }
+
+    /**
+     * @return Node[]
+     */
+    public function getNodes()
+    {
+        return $this->nodes;
+    }
+}

src/Phpml/NeuralNetwork/Node/Bias.php

@@ -0,0 +1,18 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace Phpml\NeuralNetwork\Node;
+
+use Phpml\NeuralNetwork\Node;
+
+class Bias implements Node
+{
+    /**
+     * @return float
+     */
+    public function getOutput(): float
+    {
+        return 1.0;
+    }
+}

src/Phpml/NeuralNetwork/Node/Input.php

@@ -0,0 +1,39 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace Phpml\NeuralNetwork\Node;
+
+use Phpml\NeuralNetwork\Node;
+
+class Input implements Node
+{
+    /**
+     * @var float
+     */
+    private $input;
+
+    /**
+     * @param float $input
+     */
+    public function __construct(float $input = 0.0)
+    {
+        $this->input = $input;
+    }
+
+    /**
+     * @return float
+     */
+    public function getOutput(): float
+    {
+        return $this->input;
+    }
+
+    /**
+     * @param float $input
+     */
+    public function setInput(float $input)
+    {
+        $this->input = $input;
+    }
+}

src/Phpml/NeuralNetwork/Node/Neuron.php

@@ -5,6 +5,7 @@ declare (strict_types = 1);
 namespace Phpml\NeuralNetwork\Node;
 
 use Phpml\NeuralNetwork\ActivationFunction;
+use Phpml\NeuralNetwork\Node\Neuron\Synapse;
 use Phpml\NeuralNetwork\Node;
 
 class Neuron implements Node

src/Phpml/NeuralNetwork/Node/Neuron/Synapse.php

@@ -2,11 +2,11 @@
 
 declare (strict_types = 1);
 
-namespace Phpml\NeuralNetwork\Node;
+namespace Phpml\NeuralNetwork\Node\Neuron;
 
 use Phpml\NeuralNetwork\Node;
 
-class Synapse implements Node
+class Synapse
 {
     /**
      * @var float

tests/Phpml/NeuralNetwork/LayerTest.php

@@ -0,0 +1,56 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace tests\Phpml\NeuralNetwork;
+
+use Phpml\NeuralNetwork\Node\Bias;
+use Phpml\NeuralNetwork\Layer;
+use Phpml\NeuralNetwork\Node\Neuron;
+
+class LayerTest extends \PHPUnit_Framework_TestCase
+{
+    public function testLayerInitialization()
+    {
+        $layer = new Layer();
+
+        $this->assertEquals([], $layer->getNodes());
+    }
+
+    public function testLayerInitializationWithDefaultNodesType()
+    {
+        $layer = new Layer($number = 5);
+
+        $this->assertCount($number, $layer->getNodes());
+        foreach ($layer->getNodes() as $node) {
+            $this->assertInstanceOf(Neuron::class, $node);
+        }
+    }
+
+    public function testLayerInitializationWithExplicitNodesType()
+    {
+        $layer = new Layer($number = 5, $class = Bias::class);
+
+        $this->assertCount($number, $layer->getNodes());
+        foreach ($layer->getNodes() as $node) {
+            $this->assertInstanceOf($class, $node);
+        }
+    }
+
+    /**
+     * @expectedException \Phpml\Exception\InvalidArgumentException
+     */
+    public function testThrowExceptionOnInvalidNodeClass()
+    {
+        new Layer(1, \stdClass::class);
+    }
+
+    public function testAddNodesToLayer()
+    {
+        $layer = new Layer();
+        $layer->addNode($node1 = new Neuron());
+        $layer->addNode($node2 = new Neuron());
+
+        $this->assertEquals([$node1, $node2], $layer->getNodes());
+    }
+}

tests/Phpml/NeuralNetwork/Node/BiasTest.php

@@ -0,0 +1,17 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace tests\Phpml\NeuralNetwork\Node;
+
+use Phpml\NeuralNetwork\Node\Bias;
+
+class BiasTest extends \PHPUnit_Framework_TestCase
+{
+    public function testBiasOutput()
+    {
+        $bias = new Bias();
+
+        $this->assertEquals(1.0, $bias->getOutput());
+    }
+}

tests/Phpml/NeuralNetwork/Node/InputTest.php

@@ -0,0 +1,27 @@
+<?php
+
+declare (strict_types = 1);
+
+namespace tests\Phpml\NeuralNetwork\Node;
+
+use Phpml\NeuralNetwork\Node\Input;
+
+class InputTest extends \PHPUnit_Framework_TestCase
+{
+    public function testInputInitialization()
+    {
+        $input = new Input();
+        $this->assertEquals(0.0, $input->getOutput());
+
+        $input = new Input($value = 9.6);
+        $this->assertEquals($value, $input->getOutput());
+    }
+
+    public function testSetInput()
+    {
+        $input = new Input();
+        $input->setInput($value = 6.9);
+
+        $this->assertEquals($value, $input->getOutput());
+    }
+}

tests/Phpml/NeuralNetwork/Node/Neuron/SynapseTest.php

@@ -2,10 +2,10 @@
 
 declare (strict_types = 1);
 
-namespace tests\Phpml\NeuralNetwork\Node;
+namespace tests\Phpml\NeuralNetwork\Node\Neuron;
 
+use Phpml\NeuralNetwork\Node\Neuron\Synapse;
 use Phpml\NeuralNetwork\Node\Neuron;
-use Phpml\NeuralNetwork\Node\Synapse;
 
 class SynapseTest extends \PHPUnit_Framework_TestCase
 {

tests/Phpml/NeuralNetwork/Node/NeuronTest.php

@@ -6,7 +6,7 @@ namespace tests\Phpml\NeuralNetwork\Node;
 
 use Phpml\NeuralNetwork\ActivationFunction\BinaryStep;
 use Phpml\NeuralNetwork\Node\Neuron;
-use Phpml\NeuralNetwork\Node\Synapse;
+use Phpml\NeuralNetwork\Node\Neuron\Synapse;
 
 class NeuronTest extends \PHPUnit_Framework_TestCase
 {
@@ -53,7 +53,7 @@ class NeuronTest extends \PHPUnit_Framework_TestCase
     /**
      * @param int $output
      *
-     * @return \PHPUnit_Framework_MockObject_MockObject
+     * @return Synapse|\PHPUnit_Framework_MockObject_MockObject
      */
     private function getSynapseMock($output = 2)
     {