Can someone explain this please?

I know this is from the function perms but i dont understand how it works. from this part onwards:

q = permsr(1:n-1);  % recursive calls
m = size(q,1);
P = zeros(n*m,n);
P(1:m,:) = [n*ones(m,1) q];

for i = n-1:-1:1,
   t = q;
   t(t == i) = n;
   P((n-i)*m+1:(n-i+1)*m,:) = [i*ones(m,1) t]; % assign the next m
                                               % rows in P.
end

P = V(P);
end

[Jan]

As long as neither "permsr" nor "n" is defined, wild guessing is required to answer your question. Please post the complete code and ask a specific question. How much time should I spend to explain the meaning of "m = size(q,1)" or do I have to explain the zeros command?

[matmat lab]

function P = permsr(V)
% subfunction to help with recursion

V = V(:).'; % Make sure V is a row vector
n = length(V);
if n <= 1
    P = V; 
    return; 
end

q = permsr(1:n-1);  % recursive calls
m = size(q,1);
P = zeros(n*m,n);
P(1:m,:) = [n*ones(m,1) q];

for i = n-1:-1:1,
   t = q;
   t(t == i) = n;
   P((n-i)*m+1:(n-i+1)*m,:) = [i*ones(m,1) t]; % assign the next m
                                               % rows in P.
end

P = V(P);
end

This is the full code but i dont get why is there the [n*ones(m,1) q] and like the purpose of t and q and P((n-i)*m+1:(n-i+1)*m,:) = [i*ones(m,1) t] Basically i dont understand what it is doing