Which version of Arduino are you using?
- short term patch is to comment the ~RunningAverage() from .cpp and .h but that would create a memory leak. However as long as the object is in scope and there is no need to free the internal array that should not give a problem.
I'll have to dive in this one
update:
The .h file is missing a prototype of the destructor. Add ~RunningAverage(); in the public section just under the constructor. That should fix it.
Playground article is updated.
Thanks for finding this one.
Rob