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Suppose I have some number field $K$, with its ring of integers $O_K$ = K.ring_of_integers(). If $I$ is an ideal of $O_K$ (or, if $I$ is a fractional ideal of $K$), I'd like to be able to compute with the ring $O_K/I$. For example, I'd like to be able to ask how big that ring is.

K.<omega> = NumberField(x^2+x+1)
OK = K.ring_of_integers()
R.<a,b> = OK.quo(OK.ideal(9))
R.cardinality()

gives a NotImplementedError. (Even though cardinality shows up as one of the supported methods if I type R.??).

Or, again for example, I'd like to be able to determine the ring structure of $R$, or the structure of its group of units, but none of these methods seem to actually be supported.

The type of R is sage.rings.quotient_ring.QuotientRing_generic_with_category.

What am I missing?

Suppose I have some number field $K$, with its ring of integers $O_K$ = K.ring_of_integers(). If $I$ is an ideal of $O_K$ (or, if $I$ is a fractional ideal of $K$), I'd like to be able to compute with the ring $O_K/I$. For example, I'd like to be able to ask how big that ring is.

K.<omega> = NumberField(x^2+x+1)
OK = K.ring_of_integers()
R.<a,b> = OK.quo(OK.ideal(9))
R.cardinality()

gives a NotImplementedError. (Even though cardinality shows up as one of the supported methods if I type R.??).

Or, again for example, I'd like to be able to determine the ring structure of $R$, or the structure of its group of units, but none of these methods seem to actually be supported.

The type of R is sage.rings.quotient_ring.QuotientRing_generic_with_category.

What am I missing?

Suppose I have some number field $K$, with its ring of integers $O_K$ = K.ring_of_integers(). If $I$ is an ideal of $O_K$ (or, if $I$ is a fractional ideal of $K$), I'd like to be able to compute with the ring $O_K/I$. For example, I'd like to be able to ask how big that ring is.

K.<omega> = NumberField(x^2+x+1)
OK = K.ring_of_integers()
R.<a,b> = OK.quo(OK.ideal(9))
R.cardinality()

gives a NotImplementedError. (Even though cardinality shows up as one of the supported methods if I type R.??).

Or, again for example, I'd like to be able to determine the ring structure of $R$, or the structure of its group of units, but none of these methods seem to actually be supported.

The type of R is sage.rings.quotient_ring.QuotientRing_generic_with_category.

What am I missing?