Merge pull request #31 from punkka/rounding-fix

Fix of the rounding error for negative numbers, from @punkka .
Coder-Spirit · Apr 3, 2015 · c76a4f1 · c76a4f1
2 parents d47cf15 + bacb07c
commit c76a4f1
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Showing 3 changed files with 13 additions and 2 deletions.
diff --git a/src/Decimal.php b/src/Decimal.php
@@ -858,9 +858,12 @@ private static function innerRound($value, $scale = 0)
         $diffDigit = bcsub($value, $rounded, $scale+1);
         $diffDigit = (int)$diffDigit[strlen($diffDigit)-1];
 
-        if ($diffDigit >= 5) {
+        if ($diffDigit >= 5 && $value[0] !== '-') {
             $rounded = bcadd($rounded, bcpow('10', -$scale, $scale), $scale);
         }
+        if ($diffDigit >= 5 && $value[0] === '-') {
+            $rounded = bcsub($rounded, bcpow('10', -$scale, $scale), $scale);
+        }
 
         return $rounded;
     }

diff --git a/tests/Decimal/DecimalCosTest.php b/tests/Decimal/DecimalCosTest.php
@@ -12,7 +12,7 @@ public function cosProvider() {
         return array(
             array('1', '0.54030230586814', 14),
             array('123.123', '-0.82483472946164834', 17),
-            array('15000000000', '-0.72218064388924347681', 20)
+            array('15000000000', '-0.72218064388924347683', 20)
         );
     }
 

diff --git a/tests/Decimal/DecimalRoundTest.php b/tests/Decimal/DecimalRoundTest.php
@@ -23,6 +23,14 @@ public function testRoundWithDecimals()
         $this->assertTrue(Decimal::fromString('3.44')->round(1)->equals(Decimal::fromString('3.4')));
     }
 
+    public function testNegativeRoundWithDecimals()
+    {
+        $this->assertTrue(Decimal::fromString('-5.59059956723478932512')->round(3)->equals(Decimal::fromString('-5.591')));
+        $this->assertTrue(Decimal::fromString('-5.59059956723478932512')->round(4)->equals(Decimal::fromString('-5.5906')));
+        $this->assertTrue(Decimal::fromString('-5.59059956723478932512')->round(5)->equals(Decimal::fromString('-5.59060')));
+        $this->assertTrue(Decimal::fromString('-5.59059956723478932512')->round(6)->equals(Decimal::fromString('-5.590600')));
+    }
+
     public function testNoUsefulRound()
     {
         $this->assertTrue(Decimal::fromString('3.45')->round(2)->equals(Decimal::fromString('3.45')));