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

[Jon Awbrey]

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TOP.  Commentary Note 39

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Coupon.

Coupon is a transformation of ideas that is composed of
the 'on'-field selector Trip followed by the specialized
search operator Coup.  The following figure illustrates
a typical situation in which the Coupon operator applies:

                       o------------o
         o-------------|---------o  |
         |  o---o  o---o  o---o  |  |
         o->| m |->| ) |->| n |--o  |
            o---o  o---o  o---o     |
            ^             ^         |
            |      o------|---------o
            |     /       |
trip (this) |    /        | coupon (this)
            |   /         @
            |  /
     o------|-/---------------------o
     |  o---o< o---o  o---o  o---o  |
     o->| ( |->| a |->| b |->| c |--o
        o---o  o---o  o---o  o---o
        ^
   this |
        @

function coupon (this: idea): idea;
begin
 coupon := coup (trip (this))
end;

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