//結果為0.468CGFloat tFloat = (CGFloat)375/800;//結果為0CGFloat tFloat = 375/800;//結果為0CGFloat tFloat = 1/0;//結果為+lnf 代表正無窮CGFloat tFloat = （CGFloat）1/0;

        float numberToRound;

    int result;

    numberToRound = 4.51;

    result = (int)roundf(numberToRound);

    NSLog(@"roundf(%f) = %d", numberToRound, result); // roundf(4.510000) = 5

    result = (int)ceilf(numberToRound);

    NSLog(@"ceilf(%f) = %d", numberToRound, result); // ceilf(4.510000) = 5

    result = (int)floorf(numberToRound);

    NSLog(@"floorf(%f) = %d", numberToRound, result); // floorf(4.510000) = 4

    numberToRound = 10.49;

    result = (int)roundf(numberToRound);

    NSLog(@"roundf(%f) = %d", numberToRound, result); // roundf(10.490000) = 10

    result = (int)ceilf(numberToRound);

    NSLog(@"ceilf(%f) = %d", numberToRound, result); // ceilf(10.490000) = 11

    result = (int)floorf(numberToRound);

    NSLog(@"floorf(%f) = %d", numberToRound, result); // floorf(10.490000) = 10

    numberToRound = -2.49;

    result = (int)roundf(numberToRound);

    NSLog(@"roundf(%f) = %d", numberToRound, result); // roundf(-2.490000) = -2

    result = (int)ceilf(numberToRound);

    NSLog(@"ceilf(%f) = %d", numberToRound, result); // ceilf(-2.490000) = -2

    result = (int)floorf(numberToRound);

    NSLog(@"floorf(%f) = %d", numberToRound, result); // floorf(-2.490000) = -3

    numberToRound = -3.51;

    result = (int)roundf(numberToRound);

    NSLog(@"roundf(%f) = %d", numberToRound, result); // roundf(-3.510000) = -4

    result = (int)ceilf(numberToRound);

    NSLog(@"ceilf(%f) = %d", numberToRound, result); // ceilf(-3.510000) = -3

    result = (int)floorf(numberToRound);

    NSLog(@"floorf(%f) = %d", numberToRound, result); // floorf(-3.510000) = -4