#import <Foundation/Foundation.h> extern double add(double x,double y); extern double subtract(double x,double y); extern double multiply(double x,double y); extern double divide(double x,double y);
#import <Foundation/Foundation.h> #import "MathOperation.h" BOOL isAnOperator(const char value) { return ((value == '+')||(value == '-')||(value =='*')||(value == '/')); } int main(int argc,const char * argv[]) { double result = 0; char operator = '