Hi!
On 2013-03-31, Dima Pasechnik <[email protected]> wrote:
> On 2013-03-30, tvn <[email protected]> wrote:
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>>
>> In sympy there's a method call as_coeffficients_dict() that returns all
>> the terms and their coefficients from an expression. I am if I can do
>> something like this in Sage.
> you can do a similar thing, except that the monomials are encoded by
> their exponents
>
> sage: R.<x,a> = ZZ[]
> sage: p=x^2*a-a^2+a-4
Note that this is not a symbolic expression, but a "proper" polynomial.
But the original question was about symbolic expressions. Perhaps the
original poster has a reason for using symbolic expressions?
Perhaps the following does what is requested?
sage: var('x','a')
(x, a)
sage: b = (3*x + a*x + 4)
sage: b.operands()
[a*x, 3*x, 4]
It would probably not be too dificult to extract the constant
coefficient of each operand.
It all depends on what answer you would expect. Say, if you present an
equal polynomial symbolic expression by
sage: c = (3+a)*x + 4
Then you get
sage: c.operands()
[(a + 3)*x, 4]
Is this what you want? Or do you want that an automatic expansion into a
sum takes place? In this case it might really be better to use
polynomials.
Cheers,
Simon
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