Linker/Parser error

I'm trying to learn Objective-C and my program (creating a calculator) gets linker or parser error that I'm not able to figure out. I don't know what can cause this problem. I'm using Xcode 4.1

#include <Foundation/Foundation.h>

@interface Calculator: NSObject
{
    double accumulator; 
}
// accumulator methods
- (void) setAccumulator: (double) value; 
- (void) clear;
-(double) accumulator;

// arithmetic methods
-(void) add: (double) value; 
-(void) subtract: (double) value; 
-(void) multiply: (double) value; 
-(void) divide: (double) value; 
@end

@implementation Calculator
-(void) setAccumulator: (double) value 
{
    accumulator = value; 
}
-(void) clear {
    accumulator = 0; 
}
-(double) accumulator {
    return accumulator; 
}
-(void) add: (double) value {
    accumulator += value; 
}
-(void) subtract: (double) value {
    accumulator -= value; 
}
-(void) multiply: (double) value {
    accumulator *= value; 
}
-(void) divide: (double) value {
    accumulator /= value; 
}
@end

int main (int argc, char *argv[]) 
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; 
    double value1, value2;
    char operator;
    Calculator *deskCalc = [[Calculator alloc] init];
    NSLog (@"Type in your expression.");
    scanf ("%lf %c %lf", &value1, &operator, &value2);

    [deskCalc setAccumulator: value1]; 
    if ( operator == '+' )
        [deskCalc add: value2]; 
    else if ( operator == '-' )
        [deskCalc subtract: value2]; 
    else if ( operator == '*' )
        [deskCalc multiply: value2]; 
    开发者_JAVA百科else if ( operator == '/' )
        [deskCalc divide: value2];
    NSLog (@"%.2f", [deskCalc accumulator]); 
    [deskCalc release];
    [pool drain]; 
    return 0;
}

I'm guessing it has to do something with the header?!?!? the exact error messages are :

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h
/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:299:1: error: expected identifier or '(' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:301:19: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:302:44: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:304:19: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:305:43: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:307:19: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:307:50: error: unknown type name 'Protocol' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:308:19: error: unknown type name 'Protocol' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:308:50: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:312:30: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:312:53:{312:53-312:76}: error: format argument not an NSString [3]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:313:31: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObjCRuntime.h:313:63:{313:63-313:86}: error: format argument not an NSString [3]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSZone.h
/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSZone.h:8:1: error: expected identifier or '(' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSZone.h:16:52: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSZone.h:17:19: error: unknown type name 'NSString' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h
/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:8:1: error: expected identifier or '(' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:9:1: error: expected identifier or '(' [1]

/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:13:1: error: expected identifier or '(' [1]

fatal error: too many errors emitted, stopping now [-ferror-limit=]

I'm not able to see anything like a foundation tool as mentioned in the answers. Here is a screenshot :

Program from the book example : Programming in Objective C (3rd edition) - Pg 125

---

You may not have chose the correct Foundation project template:

So check that the Foundation Framework is included in your project:

From the second image below, type in Foundation and select "Foundation.framework", then "Clean" and "Build" again.

---

Another thing to try: rename your code file from *.cpp to *.mm

---

When you created the project, you chose C as the type. Try Foundation instead.

---

Use #import <Foundation/Foundation.h>

#import is better than #include ... it guarantees that the imported header is introduced only once.

Make sure you have "Foundation" in your project frameworks.