On 1 October 2013 13:46, Ursula Whitcher <whitc...@uwec.edu> wrote:
> I recently learned that if A is a polynomial ring in Sage in variables x, y,
> and z, the command
>
> A({tuple([1,1,1]):1})
>
> returns x*y*z.
>
> Can somebody explain this syntax to me? I understand tuple([1,1,1]), but
> what are the curly brackets and the colon doing?
The argument is a python dict, which you should read up about for more
details. It's a collection of key:value pairs. Here the keys are
tuples giveing the vector of exponents and the values are the
coefficients. In your example there is only one term, the exponent
tuple is [1,1,1] and the coefficient is 1. You could also write
sage: A({(1,1,1):1})
since the key must be a tuple like (1,1,1) and not a list like [1,1,1]
(these are Python basics).
>
> Also, is there a reason that A.monomial([1,1,1]) does not return the same
You did not make precise what type your A is but if I define
sage: A.<x,y,z> = QQ[]
sage: A
Multivariate Polynomial Ring in x, y, z over Rational Field
sage: type(A)
<type
'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomialRing_libsingular'>
then A has no method called "monomial".
John Cremona
> result?
>
> --Ursula.
>
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