Does sympy break CyclotomicField?

asked 2023-08-17 13:49:15 +0100

Alex Karenin
81 ●3 ●4 ●10

One can define a cyclotomic field as CyclotomicField(16) for example. But the code below crashes:

from sympy import *
CyclotomicField(16) 
... 
File ~/Soft/sage/src/sage/rings/integer.pyx:714, in sage.rings.integer.Integer.__init__()
    712                 return
    713 
--> 714             raise TypeError("unable to coerce %s to an integer" % type(x))
    715 
    716 def __reduce__(self):

TypeError: unable to coerce <class 'sympy.core.numbers.Integer'> to an integer

Am I doing something wrong? Is my sage broken? I would like to use sympy and CyclotomicField in the same program. Specs: Sage 9.8, 10.0, Ubuntu 22.04.

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answered 2023-08-18 17:13:15 +0100

slelievre
17684 ●22 ●160 ●349 http://carva.org/samue...

The breakage comes from importing SymPy's Integer.

Indeed, in Sage, the input 16 is preparsed as Integer(16).

Usually Integer means sage.rings.integer.Integer.

However after the line

from sympy import *

this is overridden and Integer now means sympy.core.numbers.Integer.

It seems the CyclotomicField constructor cannot cope with a SymPy Integer.

That should probably be fixed in Sage.

In the meantime, here are some possible workarounds. Each should work separately, no need to combine them.

a. Only import from sympy what you need, rather than *

b. After importing everything from SymPy as you did, restore Sage's Integer.

sage: reset('Integer')

c. Make sure to feed CyclotomicField an appropriate integer.

For instance, either a Python int or a Sage Integer, with one of the following:

sage: CyclotomicField(16r)  # r for raw -> Python int
sage: CyclotomicField(int(16))
sage: CyclotomicField(ZZ(16))
sage: CyclotomicField(sage.rings.integer.Integer(16))

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Comments

Perhaps, CyclotomicField itself should perform conversion of a given argument to whatever integer type it wants.

Max Alekseyev ( 2023-08-18 18:09:44 +0100 )edit

I agree. A similar fix was contributed by Vincent Delecroix in

Sage Trac ticket 30849: Make gcd/lcm interact better with pari and gmpy2

slelievre ( 2023-08-18 23:06:59 +0100 )edit

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