Asir - setmod

If the argument is a non-negative integer prime, GF(prime) is set as the current base field.
If the argument is a polynomial poly, GF(2^deg(poly mod 2)) = GF(2)[t]/(poly(t) mod2) is set as the current base field.
If the arguments are a prime p and an extension degree n, GF(p^n) is set as the current base field. p^n must be less than 2^29 and if p is greater than or equal to 2^14, then n must be equal to 1.
If no argument is specified, the modulus indicating the current base field is returned. If the current base field is GF(prime), prime is returned. If it is GF(2^n), the defining polynomial is returned. If it is GF(p^n), where p^n is less than 2^14, [p,defpoly,prim_elem] is returned. Here, defpoly is the defining polynomial of the n-th extension, and prim_elem is the generator of the multiplicative group of GF(p^n).
Any irreducible univariate polynomial over GF(2) is available to set GF(2^n). However the use of defpoly_mod2() is recommended for efficiency.

[174] defpoly_mod2(100);
x^100+x^15+1
[175] setmod_ff(@@);
x^100+x^15+1
[176] setmod_ff();
x^100+x^15+1
[177] setmod_ff(2,5);
[2,x^5+x^2+1,x]