# internalEdges -- list the internal edges of a tree

## Synopsis

• Usage:
internalEdges T
• Inputs:
• Outputs:
• a list, the internal edges of T

## Description

An internal edge of a tree is an edge that is not incident to a leaf. This function lists such edges. Each entry of the list is a set of the leaves on one side of the edge.

 i1 : G = graph {{0,4},{1,4},{4,5},{5,2},{5,3}}; i2 : T = leafTree G; i3 : internalEdges T o3 = {set {0, 1}} o3 : List