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

[Jon Awbrey]

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TOP.  Commentary Note 54

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Fret.

Fret is a transformation of ideas that acts as a predicate recognizer,
in effect, computing the logical conjunction of the Lief test and the
negation of the Suspect test, with the non-nil outcome as shown below:

     o---o
     | ( |
     o---o
     ^
this | =/= suspect (this)
     o

function fret (this: idea): idea;
var here: idea;
begin
 here := nil;
 if lief (this) <> nil then
  if suspect (this) = nil then here := this;
 fret := here
end;

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