definition
existence
ex b1 being Function of [:the_set_of_l2RealSequences,the_set_of_l2RealSequences:],REAL st
for x, y being object st x in the_set_of_l2RealSequences & y in the_set_of_l2RealSequences holds
b1 . (x,y) = Sum ((seq_id x) (#) (seq_id y))
uniqueness
for b1, b2 being Function of [:the_set_of_l2RealSequences,the_set_of_l2RealSequences:],REAL st ( for x, y being object st x in the_set_of_l2RealSequences & y in the_set_of_l2RealSequences holds
b1 . (x,y) = Sum ((seq_id x) (#) (seq_id y)) ) & ( for x, y being object st x in the_set_of_l2RealSequences & y in the_set_of_l2RealSequences holds
b2 . (x,y) = Sum ((seq_id x) (#) (seq_id y)) ) holds
b1 = b2
end;