multivariable polynomials

[Siman Wong <siman@math.umass.edu>]

Hi,

I'm using pari-2.1.4 to work with two-variable polynomials, and I got a 
strange result:

	? f = x^5 - y^234*x^2 - 3*y^7
	%1 = x^5 - y^234*x^2 - 3*y^7
	? f % (x^3-1)
	%2 = (-y^234 + 1)*x^2 - 3*y^7
	? f % (y^3-1)
	%3 = 0

In order words, I cannot "mod y" !  Is that because pari can only hand
polynomials with x as the variable?

Many thanks!

Best, Siman Wong