# Bind C function and integrate with RooIntegrator1D

Hello,

i am trying to numerical integrate a C function using RooFit. Somehow I got stuck in the compilation of my code and I cannot solve the compilation error:
My code (simplified):

``````int numIntBindFunc()
{
RooRealVar x("x","x",-3,3) ;
RooAbsReal* integralFct = bindFunction("bfunc",toThePower,x) ;

RooIntegrator1D numInt1D(integralFct,.5,1.5,RooIntegrator1D::Trapezoid,1000,1e-3);
Double_t result = numInt1D.integral();

cout << " THE INTEGRAL IS: " << result << std::endl;
return 0;
}

Double_t toThePower(Double_t x)
{
return x*x;
}
``````

The error message at the compilation:

Maybe someone has an idea and could help me out!
I am using ROOT 5.28/00a and RooFit v3.14.

Thanks very much,
florian