Offer a coalescing operator

[PeachOS]

Sometimes it would be nice to have a default value operator in case a field is null.
In case a field is missing, I can use obj.value("field", 0.0). There is no pendant for null values though and I would have to write something like auto val = obj["field"].is_null() ? 0.0 : obj["field"].get<double>() which gets ugly when used for several fields.

I could imagine that an operator for such situation could be very handy. I would imagine something like the following:

// inspired from SQL
double value = obj.ifnull("field", 0.0);  // if obj["field"] is null, return 0.0

// probably not much of a use case but why not mention the more generic SQL inspired operator
double value = obj.coalesce("field1", "field2", 0.0);  // takes the first non-null value among obj["field1"], obj["field2"], and 0.0

What do you think?