### 11.1.2 Polynomials of several variables

A polynomial of several variables can be represented in different ways:

1. by a symbolic expression.
2. by a dense recursive one-dimensional representation like above.
3. by a sum of monomials with non-zero coefficients (distributed sparse representation).

   A monomial with several variables is represented by a coefficient and a list of integers (interpreted as powers of a variable list). The delimiters for monomials are %%%{ and %%%}.

   For example, 3x2y is represented by %%%{3,[2,1]%%%} with respect to the variable list [x,y], and 2x3y2z−5 xz is represented by %%%{2,[3,2,1]%%%}-%%%{5,[1,0,1]%%%} with respect to the variable list [x,y,z].

   For a sparse representation, a single variable polynomial can be regarded as a multivariate polynomial with one variable.