[R] quadratically constrained quadratic programming

[Jianhui Zhou]

Hi,

Does anybody have experience to solve an quadratic programming problem 
with quadratic constraints in R?
It seems that the package "quadprog" only handles the quadratic 
programming with linear constraint.  My probelm is to maximze 
x^T\Sigma_{xy} y,
subject to x^Tx=1, y^T\Sigma_{yy} y=1, and sum(y)<t, or sum(y)=t, where 
x and y are the variable, and the Sigma's and t are know.
Can R slove this problem, or do you know any other Fortran or C  
subroutine I can load into R to solve this problem?

Thanks in advance,
Jianhui