More undefined reference errors

[kankaristo]

Continuing from #488 and #489...

I found more undefined references with different operator functions. I thought I got them all with the last PR, but noticed that I didn't have operator/ working yet.

This is still work-in-progress and I'd like some feedback:

• I removed the friend operator/ member functions from mat2x2, mat3x3 and mat4x4.
  • I think these are left over from some older version and I can't find them in any other classes. In fact, they seem to be the only friends in the entire code base.
  • They clash with similar functions in the glm namespace (undefined reference errors if you use them).
  • Are they still used, or is it OK to remove them?
• Parameter naming for operator functions with tvec1 parameters.
  • In some places they're named v1 or v2 (because it's a vector type).
  • Other places call them scalar (one-dimensional vector, so it's a single number).
  • My previous PR called them v1 and v2, because that's what tvec2 called them, but I noticed this a bit inconsistent.
  • Which naming convention should I use (or does it matter)? Would you like for me to go over all operator functions and make them consistent?

I'd also like to take a closer look (probably tomorrow) to see if I can find any more of these. There are plenty of operators I'm not (yet) wrapping with SWIG, but I might as well get them all fixed in one go (if I find any more).

[Groovounet]

I agree that "friend operator/" looks like (very) old left over and actually U can't remember what was the use of this.

I think the conversion of tvec1 should be v1 - v2 style like other vector types. This said, I don't believe any of this is really consistent.

[kankaristo]

Alright, I think I've got them all (ready for review).

I removed const & from some operator functions where the parameter was a POD type, in order to match other functions for same type (tvec4). I added const & to other POD parameters, so that the functions would match other functions for that type (tmat2x4). I wanted to keep changes minimal, so I didn't start doing this across all types.

Both tquat and tdualquat were missing declarations for boolean operators (== and !=), so I added those.

Some operator declarations for tdualquat used tquat instead of tdualquat, so I fixed those. The unary operator- seemed to be doing what operator+ should do, and the definition for the unary operator+ was missing.

I have to admit that I don't really even know what a dual quaternion is used for (I have a limited understanding of normal quaternions), so these should really be checked by someone who knows more about them.

[Groovounet]

This is a really good work!

Thanks for contributing!
Christophe