// Solve Poisson equation using matrix synta (18 liens, comments and blank lines included)
int n=10;
func f=1.;
mesh Th=square(n,n);

// Define variationnal formulation
	macro grad(u) [dx(u),dy(u)] //
	varf a(u,v)=int2d(Th)(grad(u)'*grad(v))+on(1,2,3,4,u=0);
	varf L(u,v)=int2d(Th)(f*v);

// build matrix and seond member
	fespace Vh(Th,P1);
	matrix A=a(Vh,Vh);
	real[int] b=L(0,Vh);

// Solve the problem
Vh u=0;u[]=A^-1*b;
plot(u,wait=1,cmm="Solution of Poisson equation");