I'm having some snags trying to perform some conditional compilation based
on the magnitude of a literal:

        TecDrive = (int)(
#if ((P_GAIN < 1) && (P_GAIN > 0))
        (TemperatureError / (int)(1/P_GAIN))+
#else
        (TemperatureError * P_GAIN )+
#endif

#if ((I_GAIN < 1) && (I_GAIN > 0))
        (TemperatureIntegral / (int)(1/I_GAIN));
#else
        (TemperatureIntegral * I_GAIN));
#endif

This is part of a PI (no D) control loop.  I want to be able to specify the
various gains as literals in an include file, and I wish to be able to use
gains below 1 e.g. 0.5.  However I am using integer math, and I am basicaly
trying to make the compiler replace the multiply with a divide by 1/GAIN is
the gain is less than 1 but greater than 0.

This scheme works for integer values of 1 or greater, but whenever I try to
use a fractional value I get the error "Illegal #if line (error)".  After
some experiementation is seems that any floating point value within a #if
line throws this error e.g. #if (1.0 < 2.0)  will throw the same error.

Has anyone seen this and is it an inherent limitation of the pre-processor,
or am I (most likely) doing something stupid?

Regards

Mike

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu