What results would you expect from this test:
enum days {SUN, MON, TUE, WED, THU, FRI, SAT};

days day = TUE;

void setup()
{
#if day == SUN
     Serial.println("SUN");
#elif day == MON
     Serial.println("MON")
#elif day == TUE
     Serial.println("TUE")
#elif day == WED
     Serial.println("WED")
#elif day == THU
     Serial.println("THU")
#elif day == FRI
     Serial.println("FRI")
#elif day == SAT
     Serial.println("SAT")
#endif
}

void loop(){}

I expect to see TUE, but it prints SUN instead. This is proof of a pattern that I don't understand. The "#if" will always select the first value rather than the matching value if the value is based on an enum. 

Is this a bug or expected behavior? If it is expected, then how do I get the results I am looking for (i.e., how can I make the compiler select the correct choice to generate?

Tim,

I am almost dead stop in the water until I can determine how the compiler directives are supposed to work. I get that they don't work with enum, but my last experimented proved that the #if..#elif..#elif sequence doesn't match anything. 

Since my code already blows memory in an UNO, I have to be able to conditionally include only the code needed by this specific robot, but right now I don't seem to have the tools to do this. 

Any thoughts on this?

Bob

Hi bb,

Generic Arduino code questions are best directed to the Arduino forum. The Arduino ide works the same way.

Thanks

Tim,

I think you are missing my point. My need is to know @ compile time which classes to include in the program. If I have five different motor drivers, I only need one in the resulting program, so I am absolutely dependent on #if and #elif... and they do not work as expected. 

I can send you multiple examples that prove this. I will also post this on the Arduino forum, but I know I can count on you for good and quick feedback. 

Please take a look at the code I just sent you and you will quickly see what I mean. 

Thanks,

Bob

Cool.


This works and and prints "y"

#define x  1
#define y  2
#define state y

void setup()
{
	Serial.begin(115200);
}

void loop()
{
#if state==x
	Serial.println("x");
#elif state==y
	Serial.println("y");
#else
	Serial.println("Unkown");
#endif


}