Question

I tried to place const double NA = 1e-300; in the header file for Cocoa-Touch but Xcode doesn’t like it. However when I did this in Cocoa(64 bit MAC), it works just fine.

????????

Errors:

---

Duplicate symbol _NA in
/Users/jdl/Library/Developer/Xcode/DerivedData/iExperiment-chcmotcyeolxeacnidtlgofkcihz/Build/Intermediates/iExperiment.build/Debug-iphonesimulator/iExperiment.build/Objects-normal/i386/ViewController.o
and
/Users/jdl/Library/Developer/Xcode/DerivedData/iExperiment-chcmotcyeolxeacnidtlgofkcihz/Build/Intermediates/iExperiment.build/Debug-iphonesimulator/iExperiment.build/Objects-normal/i386/AppDelegate.o
for architecture i386

---

Command
/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/clang
failed with exit code 1

---

#import <UIKit/UIKit.h>

const double NA = 1e-300; // <------------- Error in Cocoa-Touch but not Cocoa ??  
// So where do I put this so it doesn't error out in Cocoa-Touch?? 

@interface ViewController : UIViewController
{
    UITextView *tvText;
}
@end

Answer 1

Constants defined in header files should look like this:

__unused static const double NA = 1e-300; 

The __unused is to suppress compiler warnings for unused variables, and the static prevents the constant being exposed to the linker, which will solve your problem.