[chbot] New chocolate fish challenge

[Andre Renaud]

Hi Mike,
Are you allowed loops? You can implement addition using <<, &, ^. So:

static int inc(int x)
{
        int y = 1;
        while (y) {
                int carry = x & y;
                x = x ^ y;
                y = carry << 1;
        }
        return x;
}

int fish(void)
{
        static unsigned char b = 0;

        b = inc(b);
        if (b == 60) {
                b = 0;
                return 1;
        }
        return 0;
}

More than 10 lines though. Essentially it's just the naive solution
with b++ 'unpacked' into binary operators.

Andre

On 19 November 2014 15:36, hamster <hamster at snap.net.nz> wrote:
> I'm building a jumbo LED clock (using 8" 7-segment displays) for the local
> pool, as I can't read a small analogue clock without my glasses when
> swimming. The PCBs are on their way from China as I type....
>
> So here is the challenge. Make a C function that usually returns 0, but
> returns a value of 1 once in every 60 calls calls - just like this:
>
> int chocolate_fish(void)
>
> {
>
>   unsigned counter = 0;
>
>    if(counter == 59) {
>
>       counter = 0;
>
>       return 1;
>
>    }
>
>    counter++;
>
>    return 0;
>
> }
>
> Now to make it hard. You can't use any math operations - no addition,
> subtraction multiplication or division, including the increment/decrement
> operations.
>
> Bonus points for using no more static memory than one byte, and code less
> than 10 lines - with each statement on a line of their own.
>
> Mike
>
>
>
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