SQL and parse errors

Howdy:

Running Postgres 7.1.3 on RedHat Linux 7.2, kernel 2.4.7-rel 10.

Have an SQL question, which may very well be that
I need a second pair of eyes to trouble shoot the script.

[script]
explain
select
q.qid,
q.year,
m.contract,
m.mbr_num,
m.bu,
m.mbr_sex,
m.product,
m.prov_num,
m.riskgrp,
p.c_spec_1 as spec,
date_larger(m.effdt, q.effdt) as effdt,
date_smaller(m.enddt, q.enddt) as enddt,
-->>> (date_smaller(m.enddt, q.enddt) as enddt -
date_larger(m.effdt, q.effdt) as effdt)::float8 / 30.4 as memmonth <<<--
from members m,
product p,
quarters q
where
m.prov_num=p.c_prov_num

--------- make sure *all* the spans overlap one another ----
and not (
m.enddt < q.effdt
or m.effdt > q.enddt
)
;
[/script]

I believe the problem comes from what's marked off by
the arrows. The error I get from this is:

ERROR: parser: parse error at or near "as"

If I comment that out, things work. It *used* to work
before, but for the life of me, I don't recall changing
anything ...

Where is the syntax error?

Thanks!

-X