wow, thank you. I would not have thought of using list comprehensions here.
Is there a way to do
[s for s in sol if <all of the assumptions are satisfied>]
thanks
Robin
On Fri, Dec 9, 2011 at 11:48 AM, achrzesz <achrz...@wp.pl> wrote:
>
>
> On Dec 8, 9:36 pm, robin hankin <hankin.ro...@gmail.com> wrote:
>> hello
>>
>> I have been playing with assumptions(). I want to assume a>b
>> but solve() gives me a solution which is not consistent with this:
>>
>> sage: var('a b')
>> (a, b)
>> sage: assume(a>b)
>> sage: assumptions()
>> [a > b]
>> sage: solve([a+b==2,a-b==0],a,b)
>> [[a == 1, b == 1]]
>> sage:
>>
>> How come the solution (viz a=b=1) is not consistent with my assumption()?
>>
>> --
>> Robin Hankin
>> Uncertainty Analyst
>> hankin.ro...@gmail.com
>
> Sometimes one can use workarounds:
>
> sage: var('a b')
> (a, b)
> sage: sol=solve([a+b==2,a-b==0],a,b)
> sage: [s for s in sol if s[0].rhs()>s[1].rhs()]
> []
>
> sage: sol=((x+1)*x*(x-1)==0).solve(x)
> sage: [s for s in sol if s.rhs()>0]
> [x == 1]
>
> sage: var('x y')
> sage: sol=solve([x^2-4*x+y^2==0,y^4==x^2],x,y)
> sage: [s for s in sol if all([s[0].rhs()>0,s[1].rhs()>0])]
> [[x == 3, y == sqrt(3)]]
>
> --
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--
Robin Hankin
Uncertainty Analyst
hankin.ro...@gmail.com
--
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