title: octave error: subscript indices must be either positive integers or logicals
body: <p>I'm trying to sum the product of an indexed vector and an indexed matrix like this:  </p>
  
  <pre><code>k=[0:1:N-1]  
  n=[0:1:N-1]  
  x_n = sin(pi*n)  
  N = size(x_n,2)  
  _seqgen(x_n(n)*exp(k*n/N), n, 0..N-1)  
  </code></pre>
  
  <p>but I get the error: </p>
  
  <pre><code>error: subscript indices must be either positive integers or logicals  
  </code></pre>
  
  <p>What am I missing here?  </p>
  
  <p>EDIT: I just realized that I missed the _plus function to sum the generated sequences. It should look like this:</p>
  
  <pre><code>k=[0:1:N-1]  
  n=[0:1:N-1]  
  x_n = sin(pi*n)  
  N = size(x_n,2)  
  _plus(_seqgen(x_n(n)*exp(k*n/N), n, 0..N-1))  
  </code></pre>
  
  <p>I still get the same error though...</p>