Re: strategy for .h files?

[John W. Eaton]

On 05/02/2017 04:18 PM, Rik wrote:

> Summarizing, Octave's aim is for lightweight header files.  These should
> include the minimal number of #includes necessary for the header file
> itself to compile correctly (And can you add the test you used as a
> Makefile target?).

The test I used worked on the installed set of header files.  I'll see 
if I can come up with something similar that can work in the build tree.

> Even when a class is mentioned, consider whether a
> simple forward declaration of the class is sufficient rather than including
> a complete header file.  As an example of the last point, many headers in
> the interpreter library have input or output arguments which are of type
> octave_value.  Unless the header file does actual is type converting by
> calling "octave_value (xxx)", there is no need to '#include "ov.h"' when
> "class octave_value;" will do.

Yes, as long as it is just the declaration of return type and there is 
no inline code for the function that requires calling an actual 
constructor function.

I hesitate to use similar forward declarations for std:: objects since 
we don't control how they are declared.  Sometimes using "namespace std 
{ class FOO; }" might work, but a C++ implementation could do something 
different that would cause this type of forward declaration to fail.

jwe