Michael Fawcett wrote:
On 12/3/06, Daniel Wesslén <daniel@wesslen.org> wrote:
Not all swizzlings are named, but if the one you happen to want is not provided then it is easy to create:
const indexer<bits::index_swizzle<0,0,2,0> > xxzx; const indexer<bits::index_swizzle<3,2,1,0> > wzyx; vector<4> v1, v2(1,2,3,4); v1 = v2[xxzx]; // v1 = (1,1,3,1) v1[xxzx] = v2; // error - v1[xxzx] is not a lvalue due to aliasing v1[wzyx] = v2; // v1 = (4,3,2,1)
I really dislike that syntax. Feel free to make use of the swizzle code generation macros I posted in the Vault. They generate all possible combinations so users don't have to make instances of your index_swizzle classes. You would want to replace the SWIZZLE_BODY macro with your own. It simply takes in the next permutation as a sequence, e.g. (z)(w)(y).
The only downside is that there will be no compile-time error in situations like your //error line from above.
v1.xxzx() = v2; // compiles, but doesn't make too much sense
Fair enough. I much prefer my syntax to yours, but the main reason for posting was simply to present another way to do it - both syntax and implementation. Obviously I could also generate all indexing objects, but in my experience (~3 years of using this library in computer graphics), xy and xyz are the only swizzlings (if you can even call them that) that's seen any significant use. -- Daniel Wesslén