====== Description ======

The switch node is a proxy-node that uses the value of its topic-node to select an evaluation path based on evaluation of its argument list.




====== Constraints ======

  * Minimum number of child-nodes: 0

  * Maximum number of child-nodes: no limit



====== Calculus ======
  - If the topic-node has no data then the switch node's value = 0 (undetermined)
  - Otherwise:
    - Arguments are evaluated in sequence
    - The chosen argument is the first true argument in the argument list 
    - The chosen child-node is the n<sup>th</sup> node where n is the index of the chosen argument
    - If there are no true arguments and there are more child-nodes than arguments then the chosen child-node is the (n+1)<sup>th</sup> child-node where n is the argument count.
    - If there is a chosen child-node then the value of the chosen child-node is passed as the value of the switch node
    - Otherwise the value of the switch node = 0 (undetermined)