fn swap_b(cpu: &mut Cpu) {
        let b = cpu.b();

        let r = swap(cpu, b);

        cpu.set_b(r);
    }
/// Swap low and high nibbles of `B`
Swap low and high nibbles of `B`
Swap low and high nibbles of ` B `
fn swap_b(cpu: &mut Cpu) {
        let b = cpu.b();
        let r = swap(cpu, b);
        cpu.set_b(r);
    }
fn swap_b ( cpu : & mut Cpu ) { let b = cpu . b ( ) ; let r = swap ( cpu , b ) ; cpu . set_b ( r ) ; }
Swap low and high nibbles of `B`
Swap low and high nibbles of ` B `
cpu
&mut Cpu
cpu
&mut Cpu