Comparison - replace eval (#130)

* Replace eval with strategy

* Use Factory Pattern, add tests

* Add missing dockblocks

* Replace strategy with simple object

src/Phpml/Classification/DecisionTree/DecisionTreeLeaf.php

@@ -4,6 +4,8 @@
 
 namespace Phpml\Classification\DecisionTree;
 
+use Phpml\Math\Comparison;
+
 class DecisionTreeLeaf
 {
     /**
@@ -79,12 +81,7 @@ public function evaluate($record)
         $recordField = $record[$this->columnIndex];
 
         if ($this->isContinuous) {
-            $op = $this->operator;
-            $value = $this->numericValue;
-            $recordField = (string) $recordField;
-            eval("\$result = $recordField $op $value;");
-
-            return $result;
+            return Comparison::compare((string) $recordField, $this->numericValue, $this->operator);
         }
 
         return $recordField == $this->value;

src/Phpml/Classification/Linear/DecisionStump.php

@@ -8,6 +8,7 @@
 use Phpml\Helper\OneVsRest;
 use Phpml\Classification\WeightedClassifier;
 use Phpml\Classification\DecisionTree;
+use Phpml\Math\Comparison;
 
 class DecisionStump extends WeightedClassifier
 {
@@ -236,29 +237,6 @@ protected function getBestNominalSplit(array $samples, array $targets, int $col)
         return $split;
     }
 
-    /**
-     *
-     * @param mixed  $leftValue
-     * @param string $operator
-     * @param mixed  $rightValue
-     *
-     * @return boolean
-     */
-    protected function evaluate($leftValue, string $operator, $rightValue)
-    {
-        switch ($operator) {
-            case '>': return $leftValue > $rightValue;
-            case '>=': return $leftValue >= $rightValue;
-            case '<': return $leftValue < $rightValue;
-            case '<=': return $leftValue <= $rightValue;
-            case '=': return $leftValue === $rightValue;
-            case '!=':
-            case '<>': return $leftValue !== $rightValue;
-        }
-
-        return false;
-    }
-
     /**
      * Calculates the ratio of wrong predictions based on the new threshold
      * value given as the parameter
@@ -278,7 +256,7 @@ protected function calculateErrorRate(array $targets, float $threshold, string $
         $rightLabel = $this->binaryLabels[1];
 
         foreach ($values as $index => $value) {
-            if ($this->evaluate($value, $operator, $threshold)) {
+            if (Comparison::compare($value, $threshold, $operator)) {
                 $predicted = $leftLabel;
             } else {
                 $predicted = $rightLabel;
@@ -337,7 +315,7 @@ protected function predictProbability(array $sample, $label) : float
      */
     protected function predictSampleBinary(array $sample)
     {
-        if ($this->evaluate($sample[$this->column], $this->operator, $this->value)) {
+        if (Comparison::compare($sample[$this->column], $this->value, $this->operator)) {
             return $this->binaryLabels[0];
         }
 

src/Phpml/Exception/InvalidArgumentException.php

@@ -157,4 +157,14 @@ public static function pathNotWritable(string $path)
     {
         return new self(sprintf('The specified path "%s" is not writable', $path));
     }
+
+    /**
+     * @param string $operator
+     *
+     * @return InvalidArgumentException
+     */
+    public static function invalidOperator(string $operator)
+    {
+        return new self(sprintf('Invalid operator "%s" provided', $operator));
+    }
 }

src/Phpml/Helper/OneVsRest.php

@@ -4,6 +4,8 @@
 
 namespace Phpml\Helper;
 
+use Phpml\Classification\Classifier;
+
 trait OneVsRest
 {
     /**
@@ -100,7 +102,7 @@ public function reset()
     /**
      * Returns an instance of the current class after cleaning up OneVsRest stuff.
      *
-     * @return \Phpml\Estimator
+     * @return Classifier|OneVsRest
      */
     protected function getClassifierCopy()
     {

src/Phpml/Math/Comparison.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpml\Math;
+
+use Phpml\Exception\InvalidArgumentException;
+
+class Comparison
+{
+    /**
+     * @param mixed  $a
+     * @param mixed  $b
+     * @param string $operator
+     *
+     * @return bool
+     *
+     * @throws InvalidArgumentException
+     */
+    public static function compare($a, $b, string $operator): bool
+    {
+        switch ($operator) {
+            case '>':
+                return $a > $b;
+            case '>=':
+                return $a >= $b;
+            case '=':
+            case '==':
+                return $a == $b;
+            case '===':
+                return $a === $b;
+            case '<=':
+                return $a <= $b;
+            case '<':
+                return $a < $b;
+            case '!=':
+            case '<>':
+                return $a != $b;
+            case '!==':
+                return $a !== $b;
+            default:
+                throw InvalidArgumentException::invalidOperator($operator);
+        }
+    }
+}

tests/Phpml/Math/ComparisonTest.php

@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+namespace tests\Phpml\Math;
+
+use Phpml\Math\Comparison;
+use PHPUnit\Framework\TestCase;
+
+class ComparisonTest extends TestCase
+{
+    /**
+     * @param mixed  $a
+     * @param mixed  $b
+     * @param string $operator
+     * @param bool   $expected
+     *
+     * @dataProvider provideData
+     */
+    public function testResult($a, $b, string $operator, bool $expected)
+    {
+        $result = Comparison::compare($a, $b, $operator);
+
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+    * @expectedException \Phpml\Exception\InvalidArgumentException
+    * @expectedExceptionMessage Invalid operator "~=" provided
+    */
+    public function testThrowExceptionWhenOperatorIsInvalid()
+    {
+        Comparison::compare(1, 1, '~=');
+    }
+
+    /**
+     * @return array
+     */
+    public function provideData()
+    {
+        return [
+            // Greater
+            [1, 0, '>', true],
+            [1, 1, '>', false],
+            [0, 1, '>', false],
+            // Greater or equal
+            [1, 0, '>=', true],
+            [1, 1, '>=', true],
+            [0, 1, '>=', false],
+            // Equal
+            [1,   0,  '=', false],
+            [1,   1, '==', true],
+            [1, '1',  '=', true],
+            [1, '0', '==', false],
+            // Identical
+            [1,     0, '===', false],
+            [1,     1, '===', true],
+            [1,   '1', '===', false],
+            ['a', 'a', '===', true],
+            // Not equal
+            [1,   0, '!=', true],
+            [1,   1, '<>', false],
+            [1, '1', '!=', false],
+            [1, '0', '<>', true],
+            // Not identical
+            [1,   0, '!==', true],
+            [1,   1, '!==', false],
+            [1, '1', '!==', true],
+            [1, '0', '!==', true],
+            // Less or equal
+            [1, 0, '<=', false],
+            [1, 1, '<=', true],
+            [0, 1, '<=', true],
+            // Less
+            [1, 0, '<', false],
+            [1, 1, '<', false],
+            [0, 1, '<', true],
+        ];
+    }
+}