Can't include .hh ?

Using 1.6.11. I have a tiny sketch. I click on New Tab and give it the name, "happydog.hh". I then change the sketch to

#include "happydog.hh"

I get the error, "no such file: happydog.hh"

If instead I rename it "happydog.h" or "happydog.hpp", it works.

Is there some way that I can re-configure the Arduino IDE to add .hh to its list of recognized files?

Is there some way that I can re-configure the Arduino IDE to add .hh to its list of recognized files?

Why on earth would you want to do that? There is absolutely no point I can see in doing this.
Why do you want to do this?

keraba:
Using 1.6.11. I have a tiny sketch. I click on New Tab and give it the name, "happydog.hh". I then change the sketch to

#include "happydog.hh"

I get the error, "no such file: happydog.hh"

If instead I rename it "happydog.h" or "happydog.hpp", it works.

Is there some way that I can re-configure the Arduino IDE to add .hh to its list of recognized files?

Unfortunately no. In fact, you've gotten it to recognize even more than I have, I can't even get it to recognize a hpp file.

Though I do not agree with this and I feel as if this needs to change within the Arduino IDE, the IDE only recognizes cpp and h files for C++ code. So hpp file, hh files, and other formats are not supported.

keraba:
Is there some way that I can re-configure the Arduino IDE to add .hh to its list of recognized files?

.hh sketch file support was supposedly added in This adds 'hh' and 'hpp' as valid sketch files. by Chris--A · Pull Request #3485 · arduino/Arduino · GitHub. However I also find that it doesn't work, whether with Arduino IDE 1.6.6(the first release after that PR was merged) or using the latest build. I have submitted an issue report regarding this:
Can't include .hh sketch tab · Issue #5442 · arduino/Arduino · GitHub

If you really did want to try to modify the IDE then pull request #3485 might be a guide but things have changed since that time and the file SketchData.java no longer exists but I'm sure the relevant code is still in a similar location. Since #3485 was quickly merged by the Arduino developer I'd guess that if you submitted a pull request with a fix they would be receptive to it as clearly there was an official intention for the IDE to support .hh files in this way.

AudioGoose45:
I can't even get it to recognize a hpp file.

.hpp sketch file support was added in Arduino IDE 1.6.6 so you will need to use that version or newer. Strangely, including .hpp sketch files/tabs works fine for me.

.hh and .hpp library file support was added in Arduino IDE 1.6.5 but I find that with any newer IDE version I can only include these files if I've previously included a .h file from that library(even though that is not required with Arduino IDE 1.6.5-r5). I've also submitted an issue report for this: .hh and .hpp files in libraries can only be included after a .h file from that library · Issue #5441 · arduino/Arduino · GitHub