usage: vol = gquad2dgen(funxy,limxlow,limxhigh,ylow,yhigh,bpxv,wfxv,bpyv,wfyv);
or
usage: vol = gquad2dgen(funxy,limxlow,limxhigh,ylow,yhigh,nquadx,nquady);
This function evaluates a general double integral. The limits of the
inner integration may be functions of the outer integral's variable of
integration. Such as
yhigh ghigh(y)
Vol = Int Int f(x,y) dx dy
ylow glow(y)
where
funxy = f(x,y)
limxlow = glow(y)
limxhigh = ghigh(y)
and the base points and weighting functions are found from
[bpxv,wfxv,bpyv,wfyv]=grule2dgen(nquadx,nquady);
where nquadx and nquady are the number of gauss points in the x- and
y-directions, respectively.
The first form of gquad2dgen is faster when used several times, because
the points and weights are only calculated once.
The second form of gquad2dgen is usefull if it is only called once (or a
few times).
