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

[Jon Awbrey]

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TOP.  Commentary Note 53

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Grasp.

Grasp is a transformation of ideas that acts as a predicate recognizer,
in effect, computing the logical disjunction of the Grain test and the
Suspect test, with the non-nil cases as shown in the following figures:

Case 1.  grain (this) =/= nil.

              o---o
              | x | arch (this) not in {comma, left parenthesis}
              o---o  
              ^
         this |
              @

Case 2.  suspect (this) =/= nil.

                ^             o-------o 
              o--\------------|---o   |
              |   o---o   o---o   |   |
              o-->|   |-->| ) |---o   |
                  o---o   o---o       |
                  ^                   |
                  |     o-------------o
                  |    /
                  |   /
                  |  /
          o-------|-/-------o
          |   o---o<        |
          o-->| ( |-->...---o
              o---o
              ^
         this |
              @

function grasp (this: idea): idea;
var here: idea;
begin
 here := nil;
 if this <> nil then
  if grain (this) <> nil then here := this
   else if suspect (this) <> nil then here := this;
 grasp := here
end;

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