Y/x
x + 1
0
O(x^2)
  ***   at top-level: subst(x+O(x^2),x,Mod
  ***                 ^--------------------
  *** subst: forbidden substitution t_SER , t_INTMOD.
Mod(0, 3)
  ***   at top-level: subst(1/x+O(x^2),x,M
  ***                 ^--------------------
  *** subst: impossible inverse in gsubst: Mod(0, 3).
Mod(2, 3)
-1/-y
Mod(y*x, y^2*x^2 + 1)
y*x/(y^2*x^2 + 1)
List([])
List([y*x^2])
x^2 + y^2*x^3 + O(x^4)
[;]
  ***   at top-level: subst(1,x,Mat([1,2])
  ***                 ^--------------------
  *** subst: forbidden substitution t_INT , t_MAT (1x2).
4*y^2 + O(y^3)
1 + O(x)
x + O(x^2)
  ***   at top-level: substpol(x+O(x^4),x^
  ***                 ^--------------------
  *** substpol: domain error in gdeflate: valuation(x) % 2 != 0
1
(y + 1) + (y + 1)*x + O(x^2)
Total time spent: 4
