int2[] vs int2vector in pg_catalog?

Dear hackers,

I'm wondering for the rationnal of the types used in various tables in
pg_catalog (v 7.4.2) so as to represent the very same thing:

- in pg_index, the indkey is represented by a int2vector

- in pg_constraint, conkey and confkey are represented my smallint[]

As I was trying to compare the two, I have to resort to some hacks.

It also appears that there are very few available function to deal with
int2vector at the SQL or PL/pgSQL level. Basically I found none:-(

Any comments?

-- 
Fabien Coelho - coelho@cri.ensmp.fr