[Bug-readline] partial word completion

[David Fang]

Hi,
	(Apologies if this is not appropriate for the bug list but I found 
no other readline mailing list!)
	I'm trying to perform completion on a *part* of a word like the 
following:

shell% whatis foo.bar.<TAB>

by parsing "foo.bar" to determine the context of what could follow,
I'm successfully able to generate a list of members of foo.bar:

  xx  yy  zz

But for completion, readline considers "foo.bar." the entire word, and 
after tab-completing "foo.bar.x", I'm left with only:

shell% whatis xx

The prefix was deleted/replaced.
I would like this to behave similarly to directory completion:
% cd foo/bar/x<TAB>
% cd foo/bar/xx

What additional steps do I need to be able to retain the prefix-portion of 
a word being substituted, and only substitute the tail-portion?

Thanks in advance.

Fang

David Fang
http://www.csl.cornell.edu/~fang/
http://www.achronix.com/