xnul

This function does nothing, and is a useful default callback function

internal

Implements geodesic interpolation and basis
generation functions that allow you to create new tour
methods from R.

<dl><dt>...</dt>
<dd>all arguments to <code>...</code> are ignore</dd></dl>

<dl>

<dt>...</dt>
<dd>all arguments to <code>...</code> are ignore</dd>

</dl>