Q:\FU\GROUPS.TXT

The FU and IDX groups are quite closely related.  We need to use
some theorems about functions to prove properties of id(x), and
vice-versa.  For this reason we have introduced a new group FU\3
which contains theorems about functions whose proofs need facts
about id(x).  Some of these theorems were formerly in the group
IDX3.  The rule of thumb here is that if the theorem does not
explicitly involve id(x) in its statement, but only in its proof then it does not
belong in the IDX group, but will go into the FU3 group.  So the 
order of the groups is something like this:

FU\1    Basic theorems about functions.
FU\2
OO
IDX\1   Basic theorems about id(x).
IDX\2
IDX\3
FU\3    Advanced theorems about functions.

We are not making a big distinction between functions in which the
hypothesis involves functions and those for which only singlevaluedness
is required.  The distinction is rather pedantic.