table functions as fields in a select

hallo,
i am using pg7.3.4. i have written a table function in c that tokenizes
a text, returning a setof text. i can use this function either in
constructs like:
select * from tokenize( 'some text that has to be tokenized' );
or in costructs like:
select tokenize( text_field ) from some_table;
the latter gives me the whole result of all words contained in every
"text_field" of "some_table". i wonder if this is a forseen behaviour,
since doing the same with a plpgsql function does not work (the plpgsql
interpreter raises an error when it reaches the "return next" statement
telling i'm using a "set-valued function in a context that can not
accept a set"). but the c function works fine. now i'm trying the 8beta,
where my "tokenize" function does not work anymore in the second
construct. the server does not alert me, it simply returns an empy
record set. this behaviour for sure not the right one since it should
raise an error, but mainly i would really like it to work at least as it
did on 7.3.4 since, as i believe my little example shows, this can be
very useful. does anybody know what is the forseen behavior for using a
set returning function in the field list of a select and, if the answer
is "it should raise an error", if it is possible to work around it?

thanks in advance,

max.

ps: i did not subscribe the mailing list, so please use "replay all"..