{[],
update(se_lt_x, [c-(C + 2 * F + 20)]),
@ :: [a-A, c-C] =*= se_lt_y :: [d-A, f-F],
C < 100}
This joins the table being updated (table se_lt_x) on
table se_lt_y where se_lt_x.a = se_lt_y.a and
where se_lt_x.c < 200 then updates each identified row se_lt_x.c
with the specified expression.