fn dex(&mut self) -> bool {
        self.x -= 1;

        self.flags.set(Flags::N, self.x == 0);
        self.flags.set(Flags::Z, (self.x & 0x80) != 0);

        false
    }
// DEX: Decrement X
// Affects: N Z
Decrement X
Affects: N Z
Decrement X Affects : N Z
fn dex(&mut self) -> bool {
        self.x -= 1;
        self.flags.set(Flags::N, self.x == 0);
        self.flags.set(Flags::Z, (self.x & 0x80) != 0);
        false
    }
fn dex ( & mut self ) -> bool { self . x -= 1 ; self . flags . set ( Flags :: N , self . x == 0 ) ; self . flags . set ( Flags :: Z , ( self . x & 0x80 ) != 0 ) ; false }
DEX: Decrement X
Affects: N Z
DEX : Decrement X Affects : N Z
&mut self