What if it is inconvenient to define multiplication in terms of the basis (e.g. what if we don't want to work with a basis unless it is really necessary)?

What if we have infinite dimensional spaces but multiplication can
still be defined (without using a basis)?

Best
Jonas

On 28.11.2015 20:49, Travis Scrimshaw wrote:

     > Or what is the "modern" approach/solution for this?

    It is possible to do everything based on
    sage.combinat.free_module.CombinatorialFreeModule. It is a clean
    mathematical approach (for defining something like a multiplication on
    a module, it is enough to define what happens on a basis). But it is
    pure python code and it uses an amazing amount of indirections. So, I
    would recommend against using it for time-critical applications. And
    that's part of the motivation for the two tickets that I mentioned
    before:
    I want to make it possible to define a multiplication action in some
    Cython file, and let the categoy framework (written in Python) put the
    appropriate fast Cython methods into the parent's action cache.

A lot of the functionality has also been abstracted up to the category
ModulesWithBasis. However, I agree that there are a large number of
indirections that we might want to simplify, and CombinatorialFreeModule
would likely benefit from more cythonization (and common abstraction
with sparse free modules).

Best,
Travis

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