/* ************************************* */
/* Procedim  que  constroi o dig controlo*/
/*****************************************/


constroiean:=proc(ean)

local i, isbn, testePAR, testeIM, checksum, eanArray;

begin
	eanArray:=array(1..12,ean);
        testeIM:=0;
        for i from 1 to 6 do
                testeIM:=testeIM+eanArray[2*i-1]
        end_for:
        testePAR:=0;
        for i from 1 to 6 do
                testePAR:=testePAR+3*eanArray[2*i]
        end_for:
        checksum:=-(testeIM+testePAR) mod 10:
 	print(" O digito de controlo e' ",checksum):
end_proc: