Practical details Useful ingredient to handle successive algebraic extensions: AlgExtend : (A, F) 7−→ (B, g, a), where A(x) ∈ K[x] irr., F(x) ∈ K(α)[x] where A(α) = 0, and B(x) ∈ K[x] irr. g(x) ∈ K[x]: g(β) root of F(x) where B(β) = 0, a(x) ∈ K[x]: a(β) root of A(x). Nicolas Mascot Algebraic curves