expression templates

[jasonw]

bearophile Wrote:

> Regarding expression templates in C++ and D there is something to be considered (this was probably already discussed in past, but probably not by me). D is or hopes to become a language quite fit for numerics processing too. Features like vectors ops, multiple dimensional dollars symbols, array slicing, inline assembly, string mixins, operator overloading, some support for parallelism, etc, and the general low-level nature of its C roots, make it good (or acceptable) for heavy numeric processing on the CPUs (and maybe acceptable on the GPUs too).
> 
> C++ template meta-programming looks hard to, but part of the complexity comes from the syntax, weird semantics corner cases, cheap limitations etc. If you translate some C++ template meta-programming code with a functional language, you see how much semantically easy most of that C++ code is. C++ template syntax is a kludge. D templates improve the situation some and remove some wizardry from C++ templates; I have learnt to use D templates in a relatively short time.
> 
> Similarly, there's some need for active libraries like Blitz++, that improve performance of the numeric code doing with library code some of the optimizations done by Fortran compilers (Blitz++ performs tiling, reordering, collapsing, unit stride optimizations, etc.). As with template meta-programming, such optimizations are not very complex, but they become wizardry if you have to implement them with C++ templates (and maybe with D templates too).
> 
> So is D going to somehow help the implementation of those optimizations, or is this need too much niche to deserve this work?

You are right, D's templates are very similar to C++'s templates modulo syntactic improvements, static if, and so on. However this discussion should be tagged with D 3.0. The feature set of D 2.0 is already set in stone. The only way to improve this is via library addons. You could try writing patches. Maybe a set of abstraction templates would help developing better metaprograms?