function controle(kaartnr)
A::=[];
for i=1 to 15 step 1 A:=A|mod(floor(kaartnr/10^(16-i)),10); end
A:=A|mod(kaartnr,10);
som::=0;
n::=0;
for i=1 to 15 step 2 som:=som+2*A[i]; if A[i] > 4 then n:=n+1; endif end
for i=2 to 16 step 2 som:=som+A[i]; end
if mod(som+n,10) == 0
return "correct"
else
return "false"
endif
endfunction