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

[Jon Awbrey]

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TOP.  Commentary Note 57

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Lade.

Lade is a transformation of ideas that operates on
the premiss that its argument idea, if significant,
references a form in a cycle of forms.  It is used
to search the cycle in reverse order until finding
a form that passes the Lode test, in which case it
returns the address of the first such form, if any,
as its functional value, otherwise returning a nil.
The following figure illustrates a non-nil outcome:

 o-----------------------------------------o
 |   o---o   o---o         o---o   o---o   |
 o-->| a |-->| b |-->···-->| x |-->| y |---o
     o---o   o---o         o---o   o---o
     ^                     ^
this |               there | = lode (there)
     @                     @

function lade (this: idea): idea;
var here, there: idea;
begin
 here := nil;
 if this <> nil then
  begin
   there := this;
   repeat there := fore (there);
    here := lode (there)
   until (here <> nil) or (there = this)
  end;
 lade := here
end;

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