[Inquiry] Re: Theme One Program -- Commentary

[Jon Awbrey]

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TOP.  Commentary Note 18

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Belong.

Belong is a function from "casts" and ideas to ideas.
A cast is a set of characters.  The functional value of
Belong is nil unless its argument idea addresses a form
whose 'sign' field bears a character that belongs to its
argument cast, in which case its functional value is equal
to its argument idea.  In other words, Belong functions as
a membership test for characters belonging to specified sets.

function belong (such: cast;
                 this: idea): idea;
var here: idea;
begin
 here := nil;
 if this <> nil then
  if arch (this) in such then here := this;
 belong := here
end;

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Beside.

Beside is a function from "casts" and ideas to ideas.
A cast is a set of characters.  The functional value of
Beside is nil unless its argument idea addresses a form
whose 'sign' field has a character that does not belong
to its argument cast, in which case its functional value
is equal to its argument idea.  In other words, Beside is
a membership test for characters outside of specified sets.

function beside (such: cast;
                 this: idea): idea;
var here: idea;
begin
 here := nil;
 if this <> nil then
  if not (arch (this) in such) then here := this;
 beside := here
end;

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