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

[Jon Awbrey]

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TOP.  Commentary Note 47

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Sape.

Sape is a function from pairs of ideas to ideas that
acts as a specialized significance and equality test.
Its functional value is nil unless each of the two
argument ideas points to an existing form and one
of the following two cases is true:  (1) both of
the forms bear the same Atom-type character in
their respective 'sign' fields, or (2) both of
the forms contain a blank character in their
respective 'sign' fields while bearing the
same non-nil idea in their 'as'-fields,
in which cases the functional value is
equal to the second argument idea.

Case 1.  atom (that) =/= nil.  arch (that) = arch (this).

        o---o           o---o
        | a |           | a |
        o---o           o---o
        ^               ^
   that |          this | = sape (that, this)
        @               @

Case 2.  arch (that) = arch (this) = blank.

      ^ ante (that) = ^ ante (this) =/= nil
       \               \
        o---o           o---o
        |   |           |   |
        o---o           o---o
        ^               ^
   that |          this | = sape (that, this)
        @               @

function sape (that, this: idea): idea;
var here: idea;
begin
 here := nil;
 if this <> nil then
  if atom (that) <> nil then here := rapt (that, this)
   else if bank (that) <> nil then here := apse (that, this);
 sape := here
end;

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