title: how to add patch-here to a list in netlogo?
body: <p>Or how can I add coordinates to a patch-set?
  I want to create a list and add each patch visited as another element of the list (using lput) but instead the list replaces the patch-here everytime, thus I tried to use patch-set, however I don't know how to add new patches in the end of it and add coordinates there.</p>
  
  <p>Here is my code so far:</p>
  
  <pre><code>globals [ frontier frontier2 ]
  
  breed [squares square]
  breed [circles circle]
  
  to setup
    ca
    set-default-shape squares "square"
    set-default-shape circles "circle"
    create-breeds
    reset-ticks
  end
  
  to create-breeds
      create-squares 1 [
        setxy 0 0  ]
      create-circles 1 [
        setxy 5 5 ]
  end
  
  to go
    ask squares [
      fd 1
      set frontier []
      set frontier lput patch-here frontier
      show frontier
    ]
    ask circles [
      fd 1
      set frontier2 patch-set patch-here
      show frontier2
    ]
    tick
  end
  </code></pre>
  
  <p>And that's what the command center is showing:</p>
  
  <p>"(square 0): [(patch 7 -3)]</p>
  
  <p>(circle 1): (agentset, 1 patch)"</p>
  
  <p>I was expecting something like (square 0): [(patch 0 0) (patch 1 0) (patch 2 0)]</p>