Extensions to C(Chapter 2 of Learn Objective-C on the Mac)

 #import <Foundation/Foundation.h>

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

 {

   NSLog (@"Hello, Objective- C!");

   return (0);

 } // main

 

 1 #import <Foundation/Foundation.h>
 2 // returns NO if the two integers have the same
 3 // value, YES otherwise
 4 BOOL areIntsDifferent (int thing1, int thing2)
 5 {
 6   if (thing1 == thing2) 
 7   {
 8     return (NO);
 9   } 
10   else 
11   {
12     return (YES);
13   }
14 } // areIntsDifferent
15 
16 // given a YES value, return the human- readable
17 // string "YES". Otherwise return "NO"
18 NSString *boolString (BOOL yesNo)
19 {
20   if (yesNo == NO) 
21   {
22     return (@"NO");
23   } 
24   else 
25   {
26     return (@"YES");
27   }
28 } // boolString
29 
30 int main (int argc, const char *argv[])
31 {
32   BOOL areTheyDifferent;
33   areTheyDifferent = areIntsDifferent (5, 5);
34   NSLog (@"are %d and %d different? %@", 5, 5, boolString(areTheyDifferent));
35   areTheyDifferent = areIntsDifferent (23, 42);
36   NSLog (@"are %d and %d different? %@", 23, 42, boolString(areTheyDifferent));
37   return (0);
38 } // main