Added mod to decimal

Author: Stefan Majoor

src/Decimal.php

@@ -548,6 +548,7 @@ public function additiveInverse()
         return new Decimal($value, $this->scale);
     }
 
+
     /**
      * "Rounds" the Decimal to have at most $scale digits after the point
      * @param  integer $scale
@@ -620,6 +621,18 @@ public function abs()
         return $this->additiveInverse();
     }
 
+    /**
+     * Calculate modulo with a decimal
+     * @param $d
+     * @return $this % $d
+     */
+    public function mod(Decimal $d, $scale = null)
+    {
+        // integer division
+        $div = $this->div($d, 1)->floor();
+        return $this->sub($div->mul($d, $scale));
+    }
+
     public function hasSameSign(Decimal $b) {
         return $this->isPositive() && $b->isPositive() || $this->isNegative() && $b->isNegative();
     }

tests/Decimal/DecimalModTest.php

@@ -0,0 +1,31 @@
+<?php
+
+use Litipk\BigNumbers\Decimal as Decimal;
+
+/**
+ * @group mod
+ */
+class DecimalModTest extends PHPUnit_Framework_TestCase
+{
+    public function modProvider() {
+        return array(
+            array('10', '3', '1'),
+            array('34', '3.4', '0'),
+            array('15.1615', '3.156156', '2.536876'),
+            array('15.1615', '3.156156', '2.5365', 3),
+        );
+    }
+    /**
+     * @dataProvider modProvider
+     */
+    public function testMod($number, $mod, $answer, $scale = null) {
+        $numberDec = Decimal::fromString($number);
+        $modDec = Decimal::fromString($mod);
+        $decimalAnswer = $numberDec->mod($modDec, $scale);
+
+        $this->assertTrue(
+            Decimal::fromString($answer)->equals($decimalAnswer),
+            $decimalAnswer . ' must be equal to ' . $answer
+        );
+    }
+}