How to measure distance between two data

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i can't do this code in memory like register

i try but failed

process(addr_a)

begin

for i in data_a'range loop

for j in data_a'range loop

if data_a(i) = data_b(j) then

d <= addr_a - addr_b;

end if ;

distance <= d;

end loop;

end loop;

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The code I suggested was for shift register(not ram). even then you have to use d(i) not just d

if you want to use ram then use two rams one for s1 and one for s2 then subtract addresses without the need for loop