Shortest distance between two line segments

Function computes the shortest distance between two line segments.

Computes the shortest distance between two line segments given start and end points for each. Adapts the algorithm found on Dan Sunday's website (http://softsurfer.com/Archive/algorithm_0106/algorithm_0106.htm#dist3D_Segment_to_Segment
).
Usage: Input the start and end x,y,z coordinates for two line segments.
p1, p2 are [x,y,z] coordinates of first line segment and p3,p4 are for
second line segment.

Output: scalar minimum distance between the two segments.

Example:
P1 = [0 0 0]; P2 = [1 0 0];
P3 = [0 1 0]; P4 = [1 1 0];
dist = DistBetween2Segment(P1, P2, P3, P4)
dist =

1