--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/extra/integration/quad2dggen.m	Wed Oct 10 19:54:49 2001 +0000
@@ -0,0 +1,55 @@
+function int = quad2dggen(fun,xlow,xhigh,ylow,yhigh,tol)
+%
+%usage:  int = quad2dggen('Fun','funxlow','funxhigh',ylow,yhigh)
+%or
+%        int = quad2dggen('Fun','funxlow','funxhigh',ylow,yhigh,tol)
+%
+%This function is similar to QUAD or QUAD8 for 2-dimensional integration
+%over a general 2-dimensional region, but it uses a Gaussian quadrature 
+%integration scheme.  
+%The integral is like:
+%              yhigh   funxhigh(y)
+%      int = Int     Int       Fun(x,y)  dx  dy
+%              ylow    funxlow(y)
+%
+% 	int     -- value of the integral
+%       Fun     -- Fun(x,y) (function to be integrated)
+%       funxlow -- funxlow(y)
+%       funxhigh-- funxhigh(y)
+%       ylow    -- lower y limit of integration
+%       yhigh   -- upper y limit of integration
+%       tol     -- tolerance parameter (optional)
+%Note that if there are discontinuities the region of integration 
+%should be broken up into separate pieces.  And if there are singularities,
+%a more appropriate integration quadrature should be used 
+%(such as the Gauss-Chebyshev for a specific type of singularity).
+
+%This routine could be optimized.
+
+if ( exist('tol') != 1)
+  tol=1e-3;
+elseif ( tol==[] )
+  tol=1e-3;
+endif
+
+oldint=gquad2dgen(fun,xlow,xhigh,ylow,yhigh,2,2);
+
+converge=0;
+for i=1:7
+  lim = 2^(i+1);
+  int=gquad2dgen(fun,xlow,xhigh,ylow,yhigh,lim,lim);
+
+  diff  = oldint - int;
+  limit = abs(tol*int);
+  if ( abs(diff) < limit )
+    converge=1;
+    break;
+  endif
+  oldint=int;
+endfor
+
+if ( converge==0 )
+  disp('Integral did not converge--singularity likely')
+endif
+
+endfunction