How to run loop in psql?

Hello there.

Perhaps I'm supposed to know this, but how can I run a function on
each query result in psql?

I run the query  select a,b from foo where x=y; and I would like to
run the function bar(u,v) for each result from the query and using
the values of a and b as parameters to the function.
How can I do that in psql?


Something like:

for x in select a,b from foo where x=y loop
    select bar(x.a,x.b);
end loop;

would be great!