// Program for solving Poisson problem with homogeneous boundary conditions

int Nbnodes=10;  // number of nodes in x and y direction
mesh Th=square(Nbnodes,Nbnodes,[x,y]); // uniform mesh of the domain

func f=1.0;  // right-hand side term

fespace Vh(Th,P1);  // FE space (Lagrange P1) defined on Th
Vh uh,vh;  // functions of the FE space

problem Poisson(uh,vh,solver=LU)=  // Definition of the variational problem
  int2d(Th)(dx(uh)*dx(vh)+dy(uh)*dy(vh))  // bilinear form
 -int2d(Th)(f*vh)                         // linear form
 +on(1,2,3,4,uh=0);                       // Dirichlet boundary conditions

plot(Th,wait=1);  // draw mesh

Poisson;          // Numerical solution

plot(uh,wait=1);  // Plot the solution