save before flutter upgrade

lib/functions/double_extensions.dart

@@ -0,0 +1,8 @@
+import 'dart:math';
+
+extension Precision on double {
+  double toPrecision(int fractionDigits) {
+    var mod = pow(10, fractionDigits.toDouble()).toDouble();
+    return ((this * mod).round().toDouble() / mod);
+  }
+}