[Cython] [ENH] Compile-time code execution (macros / templates)

[Celelibi]

Le Fri, Feb 26, 2021 at 01:32:34PM +1300, Greg Ewing a écrit :
> On 26/02/21 9:29 am, Celelibi wrote:
> > Maybe in the future if cython
> > support compiling closures to C?
> 
> Your "twice" example already needs some closure functionality.
Yes, at the python level only. That's precisely the point.

> It relies on being able to manufacture a cdef function inside
> a Python function, with the expectation that it will have
> access to arguments of the Python function. With all or some
> of that happening at compile time rather than run time. I'm
> having trouble imagining how it would be implemented.

It relies on creating a python object representing the inner cdef
function during the compile-time execution. Which is, like, the trivial
part.

Just picture the `twice` example being converted like this for the
compile-time execution.


def twice(f):
    fun = CdefFunction(... use f ...)
    return fun

foo = CdefFunction(...)
ast.append(AstCdefFunction("foo", twice(foo)))


Where CdefFunction is not necessarily callable. It's just a class
representing a cdef function. And AstCdefFunction is an AST node
representing a cdef function definition.

Does that seem far fetched to you?
I think this might even be doable without having to even detect the
closure in cython. We'd just have to let python perform the name lookup.


Celelibi