fix(#74): use normalized notation on toStringAsExponential (#73)

* refactor: use normalized notation on toStringAsExponential * remove unnecessary round * clean up Co-authored-by: Alexandre Ardhuin <alexandre.ardhuin@gmail.com>
a14n · Apr 19, 2022 · d4cc54c · d4cc54c
1 parent 266a43a
commit d4cc54c
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/lib/decimal.dart b/lib/decimal.dart
@@ -284,9 +284,17 @@ class Decimal implements Comparable<Decimal> {
       value = (value / ten).toDecimal();
       eValue++;
     }
+    value = value.round(scale: fractionDigits);
+    // If the rounded value is 10, then divide it once more to make it follow
+    // the normalized scientific notation. See https://github.com/a14n/dart-decimal/issues/74
+    if (value == ten) {
+      value = (value / ten).toDecimal();
+      eValue++;
+    }
+
     return <String>[
       if (negative) '-',
-      value.round(scale: fractionDigits).toStringAsFixed(fractionDigits),
+      value.toStringAsFixed(fractionDigits),
       'e',
       if (eValue >= 0) '+',
       '$eValue',

diff --git a/test/decimal_test.dart b/test/decimal_test.dart
@@ -308,6 +308,8 @@ void main() {
     // issue https://github.com/a14n/dart-decimal/issues/48
     expectThat(dec('1.7976931348623157e+310').toStringAsExponential(10))
         .equals('1.7976931349e+310');
+    // issue https://github.com/a14n/dart-decimal/issues/74
+    expectThat(dec('9.9999e+7').toStringAsExponential(2)).equals('1.00e+8');
   });
   test('toStringAsPrecision(int precision)', () {
     expectThat(dec('0').toStringAsPrecision(1)).equals('0');