temporary fix to reload error - json is alphabetical - TODO: potentia…

…lly check the max length dynamically zero pad

ceil(log10(maxlen)) zero padding would do but maybe we should store a new "maxlength" key

include/data/FluidJSON.hpp

@@ -140,11 +140,13 @@ void to_json(nlohmann::json &j, const FluidDataSeries<std::string, T, 1> &ds) {
   auto ids = ds.getIds();
   auto data = ds.getData();
   j["cols"] = ds.pointSize();
-  for (index r = 0; r < ds.size(); r++) 
-  {
+  char timestring[6];
+  for (index r = 0; r < ds.size(); r++) {
     auto series = data[r];
-    for (index s = 0; s < series.rows(); s++)
-      j["data"][ids[r]]["t" + std::to_string(s)] = data[r].row(s);
+    for (index s = 0; s < series.rows(); s++) {
+      std::snprintf(timestring,6,"T%04ld",s);
+      j["data"][ids[r]][timestring] = data[r].row(s);
+    }
   }
 }