// Solve Poisson equation on a square (basic example, 15 lines comments and blank lines included)

int n=10;
func f=1.;
mesh Th=square(n,n);
fespace Vh(Th,P1);
Vh u,v;
problem Poisson(u,v)=int2d(Th)(dx(u)*dx(v)+dy(u)*dy(v))-int2d(Th)(f*v)+on(1,2,3,4,u=0);
Poisson;
plot(Th,u,wait=1,cmm="Solution of Poisson equation");

// Mesh adaptation
Th=adaptmesh(Th,u,err=1.e-3);
Poisson;
plot(Th,u,wait=1,cmm="Solution of Poisson equation on adapted mesh");