mmarco a écrit :
Dealing with polynomial ringsi found something that seems incorrect
sage: R=QQ['x','y']
sage: S=QQ['x']['y']
Shouldn't there be natural coercions from rings like QQ[x,y][z] or
QQ[x][y][z] to QQ[x,y,z] and vice-versa?
One easy way to coerce is Domain("the-expression")
Dealing with polynomial ringsi found something that seems incorrect
sage: R=QQ['x','y']
sage: S=QQ['x']['y']
sage: R.has_coerce_map_from(S)
True
sage: S.has_coerce_map_from(R)
False
Even if both rings are naturally isomorphic. Moreover,
the .polynomial(y) method gives preciselly the natural map f
