Question

What is the difference between

if mi.(j) = false && m.(j).(i) = false

and

if not (mi.(j) && m.(j).(i))

Because I think it has the same meaning, but when I run the code it gives me a different answer.

Answer 1

Say mi.(j) is true and m.(j).(i) is false.

mi.(j) = false && m.(j).(i) = false
true = false && false = false
false && true
false

not (mi.(j) && m.(j).(i))
not (true && false)
not (false)
true

You probably want not (mi.(j) || m.(j).(i)). This is basically
an instance of DeMorgan’s laws.