====== Description ======
The exp node returns the exponential e to the power of the value of its child-node.

====== Constraints ======
  * Minimum number of child-nodes: 1
  * Maximum number of child-nodes: 1
  * Valid input range: no constraints, but results may under or overflow.

====== Calculus ======
The exp node's value is calculated by raising e to the power of the value of its child-node.

value = e<sup>x</sup> , where x is the value of the child-node