Hi
On Fri, Sep 23, 2011 at 9:13 PM, Aaron Meurer <[email protected]> wrote:
> If you just want to do simple arithmetic, you can use the FF class:
>
> In [1]: FF(12)
> Out[1]: ℤ₁₂
>
> In [2]: FF(12)(4)
> Out[2]: 4 mod 12
>
> In [3]: FF(12)(4)/FF(12)(11)
> Out[3]: 8 mod 12
>
> Note that the name FF comes from finite field, so this may not work if
> the modulus is not a power of a prime. For example:
>
> In [4]: FF(12)(4)/FF(12)(2)
> ---------------------------------------------------------------------------
> NotInvertible Traceback (most recent call last)
>
> /Users/aaronmeurer/Documents/python/sympy/sympy/<ipython console> in
> <module>()
>
>
> /Users/aaronmeurer/Documents/python/sympy/sympy/sympy/polys/domains/modularinteger.pyc
> in __div__(self, other)
> 92
> 93 if val is not None:
> ---> 94 return self.__class__(self.val * self._invert(val))
> 95 else:
> 96 return NotImplemented
>
>
> /Users/aaronmeurer/Documents/python/sympy/sympy/sympy/polys/domains/modularinteger.pyc
> in _invert(cls, value)
> 160 @classmethod
> 161 def _invert(cls, value):
> --> 162 return cls.dom.invert(value, cls.mod)
> 163
> 164 def invert(self):
>
>
> /Users/aaronmeurer/Documents/python/sympy/sympy/sympy/polys/domains/ring.pyc
> in invert(self, a, b)
> 39 return s % b
> 40 else:
> ---> 41 raise NotInvertible("zero divisor")
> 42
> 43 def revert(self, a):
>
> NotInvertible: zero divisor
>
> I'm not sure if you will get other errors if you use non-fields.
>
>
When I started writing gf_csolve ( Please see the pull request ) I was
aiming to add a function which solve
f(x) congruent 0 mod ( n)
where f(x) is polynomial and n is any number so I believe that should
suffice for the 1st problem.
> If you want to solve congruence relations, like x = 2 mod 3, then you
> might look at this branch: https://github.com/sympy/sympy/pull/390.
> It would be great if you could give that branch a complete review, as
> I've only been able to comment on the code quality up to this point.
>
> Aaron Meurer
>
> On Fri, Sep 23, 2011 at 2:16 AM, smichr <[email protected]> wrote:
> > I'm not sure where to look in sympy for support of things like solving
> > congruence relationships (what number is 2 mod 3, 3 mod 5 and 2 mod 7;
> > answer 23 mod 105) and operations modulo n, e.g., from
> http://tinyurl.com/3atamuj,
> > the following question:
> >
> > In Z_12, divide 4 by 2, 3, 5, 7,8, and 11
> >
> > Do we have support for such things?
> >
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> >
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--
-Regards
Hector
Whenever you think you can or you can't, in either way you are right.
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