should support like etc. on nullable arguments

darcs-hash:20040522141403-cca28-d7d84598aad7189e78b69157f61bf9e98dac8f06.gz

Author: d00bring

TODO

@@ -7,6 +7,7 @@ Things that need to be done, in no particular order:
   * Overload operators so that when they take a maybe, they always 
     return maybe, i.e. .<. may give NULL when one of the arguments
     is NULL. Suggested by eivuokko.
+  * Support like, cat etc. on nullable arguments.
   * Support all SQL datatypes
   * make SQL generation tweakable by the DB driver, since different
     DBs have different SQL syntax, for example TOP / LIMIT.