Evaluating arithmetic

youstra

In declaring an array for a timeline, I do this in DEFINE_VARIABLE:

long alDailyRegTimeline[4] =
{
(1000 * 60 * 60 * 4), // 4 AM - Towel Warm On
(1000 * 60 * 60 * 9), // 9 AM - Towel Warm Off
(1000 * 60 * 60 * 15), // 3 PM - Towel Warm On
(1000 * 60 * 60 * 21) // 9 PM - Towel Warm Off
}

I get the wrong numbers in the resulting array: 47616, 25216, 63872, 36992

Same thing w/ or w/o paren around the multiplication.

If I just do:

long alDailyRegTimeline[4] = { 14400000, 32400000, 54000000, 75600000 }

then everything's fine.

Is there something I'm missing about having the compiler do the calc? I try to break it down for readability and easy changes down the road.

Thanks,
Bill

champ

The numbers are being seen by the compiler as integers so it is rounding down the result. This is what the compiler is doing:

1000 * 60 % $10000 * 60 % $10000 * 4 % $10000

which equals 47616


Try the below statement (I haven't tested it on a master but it should work)


DEFINE_CONSTANT

LONG MSECS_IN_A_SECOND = 1000

LONG SECONDS_IN_A_MINUTE = 60
LONG MINUTES_IN_AN_HOUR = 60

LONG TOWEL_WARM_ON_AM = 4
LONG TOWEL_WARM_OFF_AM = 9
LONG TOWEL_WARM_ON_PM = 15
LONG TOWEL_WARM_OFF_PM = 21


DEFINE_VARIABLE

long alDailyRegTimeline[4] =
{
(MSECS_IN_A_SECOND
* SECONDS_IN_A_MINUTE
* MINUTES_IN_AN_HOUR
* TOWEL_WARM_ON_AM ), // 4 AM - Towel Warm On

(MSECS_IN_A_SECOND
* SECONDS_IN_A_MINUTE
* MINUTES_IN_AN_HOUR
* TOWEL_WARM_OFF_AM), // 9 AM - Towel Warm Off

(MSECS_IN_A_SECOND
* SECONDS_IN_A_MINUTE
* MINUTES_IN_AN_HOUR
* TOWEL_WARM_ON_PM ), // 3 PM - Towel Warm On

(MSECS_IN_A_SECOND
* SECONDS_IN_A_MINUTE
* MINUTES_IN_AN_HOUR
* TOWEL_WARM_OFF_PM) // 9 PM - Towel Warm Off
}

youstra

Thanks, Champ for figuring this out.

I know you can't typecast literals. I'm just surprised when I'm assigning into a long that the compiler assumes num literals are anything but long. When I do a direct assignment, it's ok...it's only if I have an arith expression that I guess it thinks the operands are not long. weird.

Guess I'll have to define another slew of constants...or maybe I'll just do the math and comment it for the maintenance guys to tweak down the road.

-Bill

DHawthorne

Yeah, this is an irritating issue for me as well, the way you can't force literals to a specific data type all the time. The format of the literal will often do this for you (like typing in 20.0 for 20 as a DOUBLE), but you can't use it in every situation (your case being the perfect example).