# Function: extensie

## CALL:

fname = extensie(fname, ext)

## DESCRIPTION:

Verify extension, append extension if needed

## INPUT:

fname | any |
    string, candidate filename
ext | any |
    string, required file extension
LEGACY | any |
    if true:
        Default behavior. Anything after "." is replaced
            extensie('donar.mat','dia')   ==> donar.dia
            extensie('donar.mat','mat')   ==> donar.mat
            extensie('gis.osm.shp','shp') ==> gis.shp
            extensie('gis.osm','shp')     ==> gis.shp

    if false:
        New behavior (20171022) if proposed file has extension already
        (or filename containing ".") and extension is different, append
        extension.
            extensie('donar.mat','dia')   ==> donar.mat.dia
            extensie('donar.mat','mat')   ==> donar.mat
            extensie('gis.osm.shp','shp') ==> gis.osm.shp
            extensie('gis.osm','shp')     ==> gis.osm.shp

## OUTPUT:

fname | any |
    string, filename including extension

## EXAMPLE:

           fname1 = extensie('donar', 'dia')
           fname2 = extensie('donar.dia', 'dia')

## APPROACH:

         Replace or append extension

      AUTHOR:
       Nanne van der Zijpp, ModelIT