Issues with ordinals module

[asmeurer]

I just noticed the new ordinals module (#13682). There are a few issues with it (sorry I didn't notice this when it was being reviewed).

• The printing should be defined in the printers in sympy.printing, not in __str__ (also side note here, methods should not define behavior for subclasses. If you want to define behavior on a subclass, put the method on the subclass. I'm referring to this line).
• Why is the class Basic? The operations produce Mul, so either the class should be Expr, or the ordinal operators should use their own classes.
• The classes should not be on S (I am removing them over at Add safe flag to sympify() #12524 so don't worry about this one).
• The str printer should print omega, since that is what the variable name is called.
• The pretty printer should use ω instead of w.
• Doing fancy stuff in __eq__ is generally considered an antipattern in SymPy (objects should compare with == structurally, not mathematically). I haven't dug into what it is actually doing, though, so this may be OK.

CC @ashishkg0022

[ashishkg0022]

We discussed a few points while implementing:

• class can't be Expr , because the addition is non - commutative.

• work was to be extended later by adding a pretty printer and a latex printer.

[asmeurer]

I see. Actually, for some reason when I was testing this before multiplying ordinals gave Mul, but now when I test it they only give Ordinal. I'm not sure what happened there.

[oscarbenjamin]

What's the status of this?

The comments above indicate that #13682 would be followed up with changes to the printers but that was 8 months ago. Did that happen?

[asmeurer]

__str__ is still defined on Ordinal so I guess not.