Hello,

I'd like to report a bug in
function:

//: true if the linesegment
joining [1], [2] meets the linesegment joining [3], [4].

export template <class
T>

bool
vgl_lineseg_test_lineseg(T x1, T y1, T x2, T y2, T x3, T y3, T x4, T y4)

This function is declared in
vgl/vgl_lineseg_test.h and is meant to determined whether two line segments
([1], [2]) and ([3], [4]) intersect.

When the inputs are:

x1 = 0; y1 = 1;

x2 = 1; y2 = 1;

x3 = 2; y3 = 1;

x4 = 3; y4 = 1;

the function returns `true',
which means the two line segments intersect while clearly these are two
completely separate, non-intersecting linesegments.

This bug occurs whenever the
two line segments lie on the same line.

A fix for this bug would be
greatly appreciated.

Nhon Trinh