Factorization over $\mathbb {Z}$/p$\mathbb {Z}$[x] : factor factoriser

factor takes as argument a polynomial with coefficients in $\mathbb {Z}$/p$\mathbb {Z}$[x].
factor factorizes this polynomial in $\mathbb {Z}$/p$\mathbb {Z}$[x] (p must be prime).
Input :

factor((-3*x^3+5*x^2-5*x+4)%13)

Output :

((1%13)*x+-6%13)*((-3%13)*x^2+-5%13)