Question

Exercise:
Write a program that converts 27° from degrees Fahrenheit (F) to degrees Celsius
(C) using the following formula:

C = (F – 32) / 1.8

Note that you don’t need to define a class to perform this calculation. Simply evaluating
the expression will suffice.

Here is my code:

#import <Foundation/Foundation.h>
int main (int argc, const char *argv[])
{
    NSAutoreleasePool *pool=[[NSAutoreleasePool alloc] init];

        float C;
        float F;
    F = 27;
    C=(F-32)/1.8;
    NSLog (@"27 degrees Fahrenheit is %f degrees Celsius." , C);
    [drain pool];
        return 0;
}

“Build failed”

On official forum there is a suggestion to write it this way :

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

   double C, F;
   F=27;
   C=(F-32)/1.8;
   int c=C;

    NSLog(@"%g degrees Fahrenheit equals %i centigrades!", F, c);

[pool drain];
    return 0;
}

But it also gives me “Failed” message.
What is not correct?

Update

Problem resolved.

I didn’t set up initial settings of my project properly.
I was working inside other “C” programming language project.
I had to just create new project-> OS X -> Command line tool (type: Foundation) unmark “Use Automatic Reference Counting”

But the best part- i was rewarded with successfully compiled program:

2012-08-09 00:20:29.214 4.2[19452:403] 27 degrees Fahrenheit is -2.777778 degrees Celsius.

Thank you @trojanfoe , @john.k.doe , @drewk , @hol

Answer 1

This works:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {            
        float C;
        float F;
        F = 27.0;
        C=(F-32.0)/1.8;
        NSLog (@"27 degrees Fahrenheit is %f degrees Celsius." , C);
    }
    return 0;
}

So does this:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    double F=27.2;
    double C=(F-32.0)/1.8;

    NSLog(@"%g degrees Fahrenheit equals %g centigrade!", F, C);

    [pool drain];
    return 0;
}