should PlanePartitions([a,b,c], symmetry=XXX) really raise an error when the dimensions do not fit?

[mantepse]

Problem Description

sage: PlanePartitions([1,2,3], symmetry="TSSCPP")

currently raises a ValueError: x, y, and z dimensions (1,2,3) must all be equal.

I think that this is unnecessary, it might be better not to. In this case, the set would simply be empty.

Here is an application: for #36124, I wanted to create the lattice of symmetries of plane partitions. Here is what I ended up doing:

def subsymmetry(A, B):
    """
    sage: D = Poset([ls, lambda A, B: A != B and subsymmetry(A, B)])
    """
    for n in range(0, 10, 2):
        AS = PlanePartitions([n]*3, symmetry=A)
        BS = PlanePartitions([n]*3, symmetry=B)
        if AS.cardinality() > BS.cardinality():
            return False
    for n in range(0, 5, 2):
        AS = PlanePartitions([n]*3, symmetry=A)
        la = AS.list()
        BS = PlanePartitions([n]*3, symmetry=B)
        lb = BS.list()
        if not set(la).issubset(lb):
            return False
    return True

It would have been nice not to iterate only over even n, but all triples [a,b,c] in a Cartesian product, this might also have been a lot faster.

Proposed Solution

Not raise the error.

Alternatives Considered

Keep the current solution. The benefit of raising an error is a clear message to the user. I guess that I could have wrapped the PlanePartitions calls with try ... except.

Additional Information

No response

Is there an existing issue for this?

• I have searched the existing issues for a bug report that matches the one I want to file, without success.

[tscrim]

@kevindilks Kevin, any thoughts about this?

[kevindilks]

I'd be fine with optional parameter like "warn" that defaults to true, and the error message could indicate that you can set warn=false if you would rather get an empty set instead of raising a warning.

I think I presumed it was more likely and more harmful that somebody doing code exploration would type in PlanePartitions([1,2,3], symmetry="TSSCPP") and just get "Set of Plane Partitions with TSSCPP symmetry in a 1x2x3 box" and start running methods without realizing it was just the empty set and not an actual thing, versus somebody trying to iterate over a large number of dimensions not being able to set up their loops to avoid passing invalid input. But optional override param would handle both cases.

[mantepse]

@kevindilks I very much like this idea! Let us try to come up with a keyword:

• check is used, I think, consistently for checking whether user input is allowed, in situations where bad user input gives wrong results or crashes sage
• warn is used only for inject_variable
• warning is used in a handful of functions where something is usually done (e.g. a normalization) but cannot for the specific input
• allow_empty is used only generating LaTeX code in a private function in an educational module.

I think I like allow_empty=False best, what do you think?