alter table question for 7.2

hi,

can anyone tell me the right way to do something like

alter table foo add column bar int not null default '0';

in a postgresql 7.2 database?

all i managed to do was to add the column and alter it to have "default
'0'".
neither where the fields filled with "0" (like they are when i do this
in postgresql 8.1) nor did i manage to add the "not null" constraint.

thx for help
matthias