Error referencing a custom function within a view

Question

The view I'm working on works fine if I leave it without a function I'm using to calculate which gpa to use, likewise the function I designed works fine on its own.
However when I add the bolded line below, to my view I get a "Missing Expression" error when I try to create the view. I'm guessing this is some silly mistake on my part, but I'd appreciate if someone could point me in the right direction as all my searching on these forums hasn't turned up anything.
I've tried various changes in formatting such as removing the as CALC_GPA and nesting the function in a sub-query. All ended up with the same error.
Lastly the select statement does work with the function on its own, it only fails when I try to make it into a view.
create view AR_SCHOLARSHIP_GPA as
select SPRIDEN_PIDM "PIDM_KEY",SPRIDEN_ID "STUDENT_ID",SPRIDEN_LAST_NAME "LAST_NAME",
SPRIDEN_FIRST_NAME "FIRST_NAME",
(select SUM(SHRTGPA_QUALITY_POINTS)/SUM(SHRTGPA_GPA_HOURS)
     from SATURN.SHRTGPA
     where pa.SPRIDEN_PIDM = SHRTGPA_PIDM
     and SHRTGPA_GPA_TYPE_IND = 'I'
     and SHRTGPA_GPA_HOURS > 0) "INST_GPA",
(select MAX(SORDEGR_GPA_TRANSFERRED)
     from SATURN.SORDEGR
     where pa.SPRIDEN_PIDM = SORDEGR_PIDM) "PCOL_GPA",
(select MAX(SORHSCH_GPA)
     from SATURN.SORHSCH
     where pa.SPRIDEN_PIDM = SORHSCH_PIDM) "HSCH_GPA",
ZFINDGPA(pa.SPRIDEN_PIDM) as CALC_GPA,
(select MAX(SORTEST_TEST_SCORE)
     from SATURN.SORTEST
     where pa.SPRIDEN_PIDM = SORTEST_PIDM
     and SORTEST_TESC_CODE = 'SATV') "SAT_VERBAL",
(select MAX(SORTEST_TEST_SCORE)
     from SATURN.SORTEST
     where pa.SPRIDEN_PIDM = SORTEST_PIDM
     and SORTEST_TESC_CODE = 'SATM') "SAT_MATH"
from SATURN.SPRIDEN pa
where SPRIDEN_CHANGE_IND is null
and ((select SUM(SHRTGPA_QUALITY_POINTS)/SUM(SHRTGPA_GPA_HOURS)
     from SATURN.SHRTGPA
     where pa.SPRIDEN_PIDM = SHRTGPA_PIDM
     and SHRTGPA_GPA_TYPE_IND = 'I'
     and SHRTGPA_GPA_HOURS > 0) >= 3.25
or ((select NVL(SUM(SHRTGPA_GPA_HOURS),0)
     from SATURN.SHRTGPA
     where pa.SPRIDEN_PIDM = SHRTGPA_PIDM
     and SHRTGPA_GPA_TYPE_IND = 'I') = 0
and ((select MAX(SORDEGR_GPA_TRANSFERRED)
     from SATURN.SORDEGR
     where pa.SPRIDEN_PIDM = SORDEGR_PIDM) >= 3.25
or (NOT EXISTS (select MAX(SORDEGR_GPA_TRANSFERRED)
     from SATURN.SORDEGR
     where pa.SPRIDEN_PIDM = SORDEGR_PIDM)
and (select MAX(SORHSCH_GPA)
     from SATURN.SORHSCH
     where pa.SPRIDEN_PIDM = SORHSCH_PIDM) >= 3.25))))
Thank you for any help you can provide.

Answer 1

That where clause that you're seeing is within one of the subqueries in my select statement. If you look carefully (sorry I know its a bit messy in this format) the function itself is within the main select statement, which is the same one in which I alias pa. I have tried moving the function around in the select statement, but although it continues to work as a standalone select statement, it fails as soon as I try and turn it into a view.
As for the function coding as requested:
create or replace Function ZFindGPA
(pidm_in IN number)
return number is
i_gpa number(4,2);
p_gpa number(4,2);
h_gpa number(4,2);
gpa number(4,2);
BEGIN
BEGIN
select SUM(SHRTGPA_QUALITY_POINTS)/SUM(SHRTGPA_GPA_HOURS)
into i_gpa
from SATURN.SHRTGPA
where pidm_in = SHRTGPA_PIDM
and SHRTGPA_GPA_TYPE_IND = 'I'
and SHRTGPA_GPA_HOURS > 0;
exception
when no_data_found then
i_gpa := NULL;
END;
BEGIN
select MAX(SORDEGR_GPA_TRANSFERRED)
into p_gpa
from SATURN.SORDEGR
where pidm_in = SORDEGR_PIDM;
exception
when no_data_found then
p_gpa := NULL;
END;
BEGIN
select MAX(SORHSCH_GPA)
into h_gpa
from SATURN.SORHSCH
where pidm_in = SORHSCH_PIDM;
exception
when no_data_found then
h_gpa := NULL;
END;
IF i_gpa is not null THEN
gpa := i_gpa;
ELSIF p_gpa is not null THEN
gpa := p_gpa;
ELSE
gpa := h_gpa;
END IF;
return gpa;
END;
In any case thanks for helping me look into this, I know its got me stumped :-P