Float precision errors using number_format() #37

Author: shabbyrobe

src/Decimal.php

@@ -138,9 +138,24 @@ public static function fromFloat($fltValue, $scale = null, $removeZeros = false)
             );
         }
 
-        $scale = ($scale === null) ? 16 : $scale;
+        $defaultScale = 16;
+
+        $strValue = (string) $fltValue;
+        if (preg_match("/^ (?P<int> \d*) (?: \. (?P<dec> \d+) ) E (?P<sign>[\+\-]) (?P<exp>\d+) $/x", $strValue, $capture)) {
+            if ($scale === null) {
+                if ($capture['sign'] == '-') {
+                    $scale = $capture['exp'] + strlen($capture['dec']);
+                } else {
+                    $scale = $defaultScale;
+                }
+            }
+            $strValue = number_format($fltValue, $scale, '.', '');
+        }
+
+        if ($scale === null) {
+            $scale = $defaultScale;
+        }
 
-        $strValue = number_format($fltValue, $scale, '.', '');
         if ($removeZeros) {
             $strValue = self::removeTrailingZeros($strValue, $scale);
         }

tests/Decimal/DecimalFromFloatTest.php

@@ -38,4 +38,42 @@ public function testNoFloat()
     {
         Decimal::fromFloat(5);
     }
+
+    public function floatProvider()
+    {
+        $tests = [
+            [1.1, "1.1"],
+            [1234567890.0, "1234567890"],
+            [1.1234567890, "1.123456789"],
+            [-1.1234567890, "-1.123456789"],
+            [0.000001, "0.0000010"],
+            [0.000001, "0.000001", null, !!'removeZeroes'],
+            [90.05, "90.05"],
+        ];
+
+        if (PHP_INT_SIZE) {
+            // These tests probably won't work if you're not testing on x86-64.
+            // It might also be better to mark the tests skipped. It is certainly
+            // useful to cover this functionality off though as it hits the exponent
+            // parsing in Decimal::fromFloat()
+            $tests[] = [
+                 1230123074129038740129734907810923874017283094.1, 
+                "1230123074129038665578332283019326242900934656.0000000000000000"
+            ];
+            $tests[] = [
+                 0.0000000000000000000000000000000000000000000000123412351234,
+                "0.0000000000000000000000000000000000000000000000123412351234",
+            ];
+        }
+        return $tests;
+    }
+
+    /**
+     * @dataProvider floatProvider
+     */
+    public function testFromFloat($in, $str, $scale=null, $removeZeroes=false)
+    {
+        $v = Decimal::fromFloat($in, $scale, $removeZeroes);
+        $this->assertSame($str, $v->innerValue());
+    }
 }