Cartesian Product method for Sets

[sagetrac-chrisjamesberg]

Right now, Sets has a method CartesianProduct (not to be confused with cartesian_product). The documentation says that this is the class for implementing cartesian_product. Does this belong as a method in the global namespace for sets? I can't think why the user would want this method to come up, when all it says is to use cartesian_product instead.

For instance:

S = Set([1,2])
S.CartesianProduct(S)
Traceback (click to the left of this block for traceback)
...
TypeError: __init__() takes at least 3 arguments (2 given)

Component: algebra

Keywords: Cartesian Product for sets

Author: Chris Berg

Issue created by migration from https://trac.sagemath.org/ticket/13435

[mjungmath]

comment:6

This does not reflect the current behavior as of Sage 9.2. The method CartesianProduct seems to be the "categorical version" now.

[fchapoton]

comment:7

I get the same traceback in 9.3.b6.

The question is: why does the class CartesianProduct appear as a method of any Set object ?

[mjungmath]

comment:8

I get a slightly different traceback (Sage 9.2 stable):

sage: S = Set([1,2])
sage: S.CartesianProduct(S)
 Traceback (most recent call last)
...
TypeError: __init__() missing 1 required positional argument: 'category'

Thus,

sage: S = Set([1,2])
sage: S.CartesianProduct(S, category=Sets())
The Cartesian product of (1, 2)

works perfectly.

Alternatively, one could try to meet the category of both objects by default?