Geoffrey Romer wrote:
I think you're assuming that when I said "polymorphism", I meant "inheritance and virtual functions", but "polymorphism" just means having one piece of code operate on different kinds of data. Templates are a kind of polymorphism, and that's what I'm referring to.
In the general C++ community, there is a sharp distinction between run-time and compile-time polymorphism, due to the 'zero-overhead' philosophy of C++, (ie. you don't pay for what you don't absolutely _have_ to pay for). Therefore, unqualified use of the term 'polymorphism' is normally assumed to mean run-time polymophism (simply because that was added to C++ first), although you are correct in your usage of it otherwise. The 'safe' term to use in this case is 'generic' code. Just FYI.
My question, rephrased, is just "why use templates?" What does this templated structure give you that you wouldn't get from just having a bunch of unrelated classes (rgb_color, cymk_color, etc.)? How would a programmer take advantage of your templated structure?
The idea is to write code that can operate on graphical data without assuming anything about the representation of said data. To do that efficiently in C++ is practicly a description of what templates are for.
In other words, can you give an example of how you see this library being used, in a way that wouldn't be possible (or easy) without templates?
consider a function that *someone* will need to use, that doesn't depend on the representation of the data: // where GraphContext is a TwoDimContainer with a value_type // convertable to PixelRepr template <class PixelRepr, class GraphContext> void resample(const GraphContext& from, GraphContext& to) { // ... // Dumb aliasing resampling to[x][y] = from[x*x_scale][y*y_scale]; // ... } <snip gargantuan quote placed below replies>