Hello John,
As a very regular user of these functions, I think this is useful to
have both (and luckily you don't want to remove one or the other!). For
the documentation, I agree that it could and should be clearer!
For your proposition, I am quite reluctant on using "dense" and "sparse"
in the documentation: There exist dense and sparse representations of
polynomials in Sage, and I wonder if this would not confuse users. Some
may think that f.coeffs is for densely represented polynomials and
f.coefficients for sparsely represented ones.
I think one could use as inspiration for the documentation of
f.coefficients() the case of multivariate polynomials. It states "Return
the nonzero coefficients of this polynomials in a list." I find this
formulation clear and simple enough. It is not clear to me that one
should add the part one the correlation with f.exponents() that you
proposed.
In the same vein, I would propose "Return all the coefficients of f in a
list, including the coefficients equal to zero" for f.coeffs.
Anyway, I agree and you can open a ticket, I'll be happy to review it!
Cheers,
Bruno
P.S.: On a related note, I am procrastinating for some time now the
opening of a ticket to make the interfaces of univariate polynomial
rings and multivariate polynomial rings more consistent. For instance,
the leading coefficient is f.leading_coefficient() in the former and
f.lc() in the latter. Many other things like that are a bit frustrating...
Le 26/11/2014 21:06, john_perry_usm a écrit :
Hello Sages
Last week (?) I noticed that a program I wrote was making a mistake,
because f.coeffs() and f.coefficients() return very different results:
the former provides a dense representation (with 0's), the second a
sparse one (no 0's, correlating with f.exponents()).
I like this OK, but the help string isn't clear on this: the latter
states merely, "Return the coefficients of the monomials appearing in
self;" while the former states, "Returns "self.list()." " The help on
self.list() states merely, "Returns a list with the coefficients of self."
So the difference is that one states "monomials /appearing/ in self,"
while the other does not clarify that it gives the monomials appearing
in self, which presumably means it includes monomials /not/ appearing
in self. I'm not good at these kinds of inferences, so this does not
immediately convey "dense" or "sparse representation," or not to me,
anyway.
I would propose the following:
*f.coeffs?* should state something to the effect of, "Returns all the
coefficients of a dense representation of f."
*f.coefficients?* should state something like, "Returns all the
coefficients of a sparse representation of f; that is, it returns only
the non-zero coefficients, in a list correlated with f.exponents."
(Notice the explicit statement of the correlation, reinforcing sparse
representation.)
*f.list?* should be mostly identical to f.coeffs?
I'm willing to open a ticket & author a patch to this effect, if at
least one other person agrees here.
john perry
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