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

[Jon Awbrey]

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TOP.  Commentary Note 46

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Apse.

Apse 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 a form and each of these
forms has the same non-nil idea in its 'as'-field,
in which case the second argument idea is returned
as the functional value.

The following figure illustrates the case of a non-nil result:

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

function apse (that, this: idea): idea;
begin
 apse := divert (equity (ante (that), ante (this)), this)
end;

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