[Inquiry] Re: Theme One Program -- Commentary -- Lead

[Jon Awbrey]

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TOP.  Commentary Note 58

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Lead.

Lead is a transformation of ideas that is used to navigate
a particular species of cactus graph in a particular manner.
The cases of a non-nil result are shown in the figures below:

Case 1.  grasp (this) =/= nil.
                                                 o-------o
                           o---------------------|---o   |
                           |   o---o         o---o   |   |
                           o-->| y |-->...-->| ) |---o   |
                               o---o         o---o       |
                               ^                         |
                               |      o------------------o
                               |     /
                          this |    /
                               |   /
                               |  /
         o---------------------|-/-o
         |   o---o         o---o<  |
         o-->| x |-->...-->| ( |---o
             o---o         o---o
             ^
             | lead (this) = lade (stem (this))
             @

Case 2.  grasp (this) = nil.

          o-------------------------------o
          |   o---o         o---o         |
          o-->| x |-->···-->| y |-->...---o
              o---o         o---o
              ^             ^
         this |             | lead (this) = lade (this)
              @             @

function lead (this: idea): idea;
begin
 lead := lade (upon (grasp (this), stem (this), this))
end;

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