Point inside/outside a polygon?

[Dennis Boccippio <djboccip(at)hotmail.com>]

Hi all,

Does anyone know of IDL routines for determination of whether a point 
datum is inside/outside a closed irregular polygon?  I'm told that some 
variants of this functionality are available in Matlab and Mathematica, 
was curious if anyone had implemented a solution for IDL.  My usual 
kludge to this is polyfill/mask-based, which is probably a very 
inefficient approach...

Thanks,

Dennis Boccippio