ideal in ring of integers: QQ vs number field

[Samuel Lelièvre]

Just to bring atttention to a question at math.stackexchange:

http://math.stackexchange.com/questions/1294942/mathbbq-isnt-a-number-field-for-sage

[Nils Bruin]

The same workaround that works in magma, also works in sage:

sage: K=NumberField(x-1,'a')
sage: OK=K.ring_of_integers()
sage: 3*OK/5*OK
Fractional ideal (3/5)

So at least it's possible to construct a number field in Sage that is isomorphic to QQ.