Help with conditional operator.

Hi,

Usually I understand how to use the conditional operator in C, but this one was tricky.

Code:

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if (GEN_SLIDING_ATTACKS[(RANKS[square]-1) < (FILES[square]-1) ? (RANKS[square]-1) : (FILES[square]-1)][state6Bit] & CHARBITSET[attackbit])

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GEN_SLIDING_ATTACKS[..... is an two-dimensional array, while RANKS[... and FILES[... is two one-dimensional arrays.

Could someone please explain to me where both the true and the false part in the statement ends up?
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One

The ternary operator is being used to compute the first index.

So (assuming index is of an appropriate integral type) the code is equivalent to

Code:

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    /*  first expand the ternary operator */
 
    if ((RANKS[square] - 1) < (FILES[square] - 1))
        index = RANKS[square] - 1;
    else
        index = FILES[square] - 1;

    /*  now plug that into the rest of the if() statement  */

     

    if (GEN_SLIDING_ATTACKS[index][state6Bit]  & CHARBITSET[attackbit])
          /* whatever */

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Note that I've done a literal interpretation of the code .... plenty of opportunities for making it simpler.

Whoever wrote that code was more interested in getting everything into one statement, than in clarity of code. IMHO, that has demonstrated their foolishness, no more.

Somewhat simplification: if (GEN_SLIDING_ATTACKS[min(RANKS[square], FILES[square]) - 1][state6Bit] & CHARBITSET[attackbit])