6.27.6 Transforming a polynomial in internal format into a list, and conversely: convert
The convert command does many conversions (see
Section 6.23.26). Among other things, it can convert between a
polynomial in internal sparse multivariate format and a list
representing the polynomial.
To convert from a polynomial in internal sparse multivariate format to
a list:
-
convert takes one mandatory argument and one optional
argument:
-
P, a polynomial written in internal sparse
multivariate format (see Section 6.27.2).
- Optionally, list.
- convert(P ⟨, list⟩) returns a list
representing the polynomial.
Example.
Input:
p:= symb2poly(x^2 - x*y + 2y, [x,y])
Output:
%%%{1,[2,0]%%%}+%%%{-1,[1,1]%%%}+%%%{2,[0,1]%%%}
Input:
l:= convert(p,list)
or:
l:= convert(p)
Output:
⎡
⎢
⎢
⎢
⎢
⎢
⎣ | | ⎤
⎥
⎥
⎥
⎥
⎥
⎦ |
which is a list of the coefficients followed by a list of the variable
powers.
To convert from a list representing a polynomial to the polynomial in
internal sparse multivariate format:
-
convert takes two arguments:
-
L, a list representing a polynomial.
- polynom.
- convert(L,polynom) returns the polynomial in
internal sparse multivariate format (see Section 6.27.2).
Example.
Input (l from above):
l:=[[1,[2,0]],[-1,[1,1]],[2,[0,1]]]
Output:
⎡
⎢
⎢
⎢
⎢
⎢
⎣ | | ⎤
⎥
⎥
⎥
⎥
⎥
⎦ |
Input:
convert(l,polynom)
Output:
%%%{1,[2,0]%%%}+%%%{-1,[1,1]%%%}+%%%{2,[0,1]%%%}