//Probleme avec une singularite
//Domaine en L

border a(t=-1,  1.){x=t;   y=-1;   label=1;};
border b(t=-1,  0.){x=1;   y=t;    label=2;};
border c(t= 0., 1.){x=1-t; y=0.;   label=3;};
border d(t= 0., 1.){x=0.;  y=t;    label=4;};
border e(t= 0., 1.){x=-t;  y=1;    label=5;};
border f(t= 0., 1.){x=-1;  y=1-2*t;label=6;};
mesh Th = buildmesh (a(6) + b(4) + c(4) +d(4) + e(4) + f(6));

fespace Vh(Th,P1);
Vh u,v;
real error=0.01;

problem Problem1(u, v) =
    int2d(Th,qforder=2)( dx(u)*dx(v) + dy(u)*dy(v)) 
  + int2d(Th,qforder=2)(-2*pi^2*sin(pi*x)*sin(pi*y)*v)
  + on(a,b,c,d,e,f,u=0);
int i;
for (i=0;i< 4;i++)
{   
   plot(Th,wait=1);
   Problem1; 
//   cout << u[].min << " " << u[].max << endl; 
   plot(u,fill=1,wait=1);
   Th=adaptmesh(Th,u,err=error);
   u=u;	
   error = error/2;
} ;