Re: Ada generics

["Hyman Rosen" <hyman.rosen@gmail.com>]

Martin Krischik wrote:
> Dmitry A. Kazakov schrieb:
>
> > 2. Support separate compilation (1 is a premise to have this)
>
> C++ 2003 now has "export" templates which promises separate compilation.
> But it is an optional feature and only one compiler [1] implements it. I
> guess it is missing point 1 which makes it so difficult.

Remember that C++ templates support specializations while Ada generics
do not. That means that instantiating a generic will depend much more
heavily on the parameters than is the case in Ada. In the same vein,
the automatic type conversions that C++ supports and Ada does not also
affect the instantiated code. This makes compiling a template itself
not a terribly useful operation. The compiler can verify syntactical
correctness and can bind some names which are not dependent on the
parameters, but it can do very little else until instantiation.
Furthermore, because of the popularity of template metaprogramming,
compilers know to apply intensive inlining while compiling
instantiations, lessening the meaningfulness of separate compilation
even more.