How to run an algorithm with higher precision?

I would like to run my own function with higher precision (more than double precision). My problem is that i don't really understand the syntax. I have for example the following function:

function [ V_k, H_k ] = Arnoldi( A, b, K )
n=length(b);
V=zeros(n,K);
V(:,1)=b*1/norm(b);
H=zeros(K,K);
for k=1:1:K
  u=A*V(:,k);
  for j=1:1:k
      H(j,k)=V(:,j)'*u;
      u=u-H(j,k)*V(:,j);
  end
  H(k+1,k)=norm(u);
  V(:,k+1)=u*1/H(k+1,k);
V_k=V(1:n,1:K);
H_k=H(1:K,1:K);
end
end

wehre A is a n times n matrix and b is a n-dimensional vector and K a positive integer. Is it enough to use the command

digits(50)
[V,H] = vpa(Arnoldi(A,B,K))

this command doesn't work, because I have two output arguments. But the question is do I have to edit the whole code like:

function [ V_k, H_k ] = Arnoldi( A, b, K )
digits(50)
n=length(b);
V=zeros(n,K);
V(:,1)=vpa(b*1/norm(b));
H=zeros(K,K);
for k=1:1:K
  u=vpa(A*V(:,k));
  for j=1:1:k
      H(j,k)=vpa(V(:,j)'*u);
      u=vpa(u-H(j,k)*V(:,j));
  end
  H(k+1,k)=vpa(norm(u));
  V(:,k+1)=vpa(u*1/H(k+1,k));
V_k=V(1:n,1:K);
H_k=H(1:K,1:K);
end
end

and use than the command

[V,H]=Arnoldi(A,b,K)

Is the solution then more precise? This is just a short example. I would like to use higher precision for a longer code and funtcion.