In graph theory, a flow network (also known as a transportation network) is a directed graph where each edge has a capacity and each edge receives a flow. A network can be used to model traffic in a computer network, circulation with demands, fluids in pipes, currents in an electrical circuit, or anything like in which something travels through a network of nodes.

COMING SOON!

```
package org.gs.digraph
/** Edge with capacity and flow
*
* @constructor creates a new FlowEdge with start and end vertices and capacity
* @param v from vertex
* @param w to vertex
* @param capacity of edge
* @see [[https://algs4.cs.princeton.edu/64maxflow/FlowEdge.java.html]]
* @author Scala translation by Gary Struthers from Java by Robert Sedgewick and Kevin Wayne.
*/
class FlowEdge(v: Int, w: Int, val capacity: Double) extends BaseDirectedEdge {
require(v >= 0 && w >= 0 && capacity >= 0 && !capacity.isNaN,
"s invalid arg(s) v:$v w:$w capacity$capacity")
private var _flow = 0.0
/** @constructor creates a new FlowEdge with start and end vertices, capacity and flow */
def this(v: Int, w: Int, capacity: Double, flow: Double) {
this(v, w, capacity)
require(_flow >= 0 && flow <= capacity,
s"flow:${_flow} must not be negative and can't exceed capacity:$capacity")
_flow = flow
}
override def toString(): String = f"$v%d->$w%d $capacity ${_flow} "
def from(): Int = v
def to(): Int = w
def flow(): Double = _flow
def other(vertex: Int): Int = vertex match {
case `v` => w
case `w` => v
case _ => throw new IllegalArgumentException(s"Illegal endpoint vertex:${vertex}")
}
def residualCapacityTo(vertex: Int): Double = vertex match {
case `v` => _flow
case `w` => capacity - _flow
case _ => throw new IllegalArgumentException(s"Illegal endpoint vertex:${vertex}")
}
def addResidualFlowTo(vertex: Int, delta: Double): Unit = {
require(!delta.isNaN, "s invalid arg(s) vertex:$vertex delta:$delta")
vertex match {
case `v` => _flow -= delta
case `w` => _flow += delta
case _ => throw new IllegalArgumentException(s"Illegal endpoint vertex:${vertex}")
}
assert(_flow >= 0 && flow <= capacity,
s"flow:${_flow} must not be negative and can't exceed capacity:$capacity")
}
}
```