% This is a prologish variation 
% This illstrates how to use the data base to accumulate partial results
% and when complete print them out.

square( X, SX):- SX is X * X.

data(1). data(2). data(3). data(4). data(5).
data(6). data(7). data(8). data(9). data(10).

% The 'object' sum(S) has two 'methods': add and clear
:-dynamic(sum/1).
sum(0).
clear:-abolish(sum,1),assert(sum(0)).
add(I):-retract(sum(S)),S2 is S+I,asserta(sum(S2)).

summer:-data(I), square(I, I2), add(I2), fail.
summer:-sum(S),  write('The sum of data' = S), nl, clear.

go:-data(I),square(I,S), write(square(I)=S), nl,fail.
go:-write('---------------------'), nl, summer.