[Cython] Fused Types

[Sturla Molden]

Den 02.05.2011 11:15, skrev Dag Sverre Seljebotn:
>
> I.e., your question is very vague.

Ok, what I wanted to ask was "why have one syntax for interfacing C++ 
templates and another for generics?" It seems like syntax bloat to me.


> You're welcome to draft your own proposal for full-blown templates in 
> Cython, if that is what you mean. When we came up with this idea, we 
> felt that bringing the full power of C++ templates (including pattern 
> matching etc.) into Cython would be a bit too much; I think Cython 
> devs are above average sceptical to C++ and the mixed blessings of 
> templates.
>
> E.g., one reason for not wanting to do it the C++ way is the need to 
> stick largs parts of your program in header files. With fused types, 
> the valid instantiations are determined up front.

C++ templates are evil. They require huge header files (compiler 
dependent, but they all do) and make debugging a night mare. Template 
metaprogramming in C++ is crazy; we have optimizing compilers for 
avoiding that. Java and C# has a simpler form of generics, but even that 
can be too general.

Java and C# can specialize code at run-time, because there is a 
JIT-compiler. Cython must do this in advance, for which fused_types 
which will give us a combinatoral bloat of specialized code. That is why 
I suggested using run-time type information from test runs to select 
those we want.

Personally I solve this by "writing code that writes code". It is easy 
to use a Python script to generate ad print specialized C or Cython code.

Sturla