COVER

The COVER operator performs an "opaque" overlay operation.  It 
overlays the result of the EXPR onto the map "mapname".

syntax:   (COVER mapname EXPR)

operation:
  Mapname must already exist.  Non-zero values from EXPR are all
  turned to the next available category.

             110000
    EXPR --  002200 --
             000033   \          881447    Note that COVER opaquely
                      COVER -->  448877    overlays an existing
             111447   /          755788    mapname using next avail-
mapname  --  444177 --                     able category number.
             755777

aliases: cover  paint
