"Programming in objective-c" 3rd Kochan exercise 4.2 - objective-c

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;
}

Answer 2

As you are not using objects even this will do it. Plain C.
int main(int argc, const char * argv[])
{
double C, F;
F=27;
C=(F-32)/1.8;
int c=C;
printf("%g degrees Fahrenheit equals %i centigrades!", F, c);
return 0;
}
Do you need to parse the arguments and calculate based on those?