I have a function with one parameter. How can I check whether this parameter is a polynomial? (Univariate or multvariate, does'nt count which is the base ring) I want use this information in a multilevel if construction
Will something like this work?
sage: is_polynomial = lambda s: all(s.is_polynomial(v) for v in s.variables())
sage: var("x y z")
(x, y, z)
sage: is_polynomial(x)
True
sage: is_polynomial(3+x+x**7)
True
sage: is_polynomial(3+x*exp(x))
False
sage: is_polynomial(3*x*y)
True
sage: is_polynomial(3*x*y+sin(y))
False
Thank you, but it is a partial solution, becaus I do'nt know, the parameter has varibales() property or not. For example : a=2 is_polynomial(a) generates an AttributeError. I believed, the .parent() will help me, but there are rings without this property.
Ah, so you don't even know that it's an Expression, then. Maybe casting it would suffice: is_polynomial = lambda s: all(SR(s).is_polynomial(v) for v in SR(s).variables()) but I'm not clear on your use cases (and how much information you want to preserve).
Yes, I don't know, the parameter is a number or a polynom. After some preparation the algoritm is same (for example, gcd, cra). but the preparation and some little aid-functions depend on the parent ring.
So does casting your parameter explicitly into an Expression by wrapping it in SR suffice for your case, or do we need to work harder?
I think it's hard. What do you mean on 'SR suffice'?
Asked: 14 years ago
Seen: 592 times
Last updated: Nov 14 '10
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