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The only difference between MACRO("Rhino3",,,,) and and MACRO("Rhino4",,,,) is is that the first uses a single running instance of Rhino and the latter makes a new instance of rhino each time the function is executed (see Rhino Wiki). If you want to execute a script by a single running instance of Rhino, please use the "Rhino4.Interface" argument instead.
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