path.groovy

// monad state such as path-histories are encoded using reflection and self-modifying instructions

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* [choose,                                       *
*   [get,'value']  -> 5                          *
*   [get,'path']   -> [1,2,3,4]                  *
*   [plus,[zero]   -> [id]                       *
*   [mult,[one]]   -> [id]                       *                   *************************
*   [minus,[zero]] -> [id]                       *   => [plus,1] =>  * ...[get,'value'] -> 6 *
*   inst           -> [sideeffect,               *                   *************************
*                       [get,'path']             *
*                       [add,[get,'value']]]     *
*                        [eval,[id]]]            *
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