### 5.27.2 Convert from a symbolic polynomial : e2r symb2poly

e2r or symb2poly takes as argument a symbolic polynomial and either a symbolic variable name (by default x) or a list of symbolic variable names.
e2r or symb2poly transforms the polynomial into a list (dense representation of the univariate polynomial, coefficients written by decreasing order) or into a sum of monomials (sparse representation of multivariate polynomials).
Input :

e2r(x`^`2-1)

or :

symb2poly(x`^`2-1)

or :

symb2poly(y`^`2-1,y)

or :

e2r(y`^`2-1,y)

Output :

1,0,-1

Input :

e2r(x`^`2-x*y+y, [x,y])

or :

symb2poly(x`^`2-x*y+2*y, [x,y])

Output :

%%%{1,[2,0]%%%}+%%%{-1,[1,1]%%%}+%%%{2,[0,1]%%%}