浮点函数返回值

Question

I am writing my object first app and i can't understand why compiler gives my errors. (With int codes works... )

#import <Foundation/Foundation.h>

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

    @autoreleasepool {


        // 1st var
        NSLog(@"Hi, %f World!", res(1.0f, 2.0f, 3.0f));

    }
    return 0;
}
float res (float a, float b, float c)
{
    float res=a+b+c;
    return res;
}

Answer 1

Try declaring res before main, so that it is known to the compiler when it founds it in main . If you don't declare it beforehand, what happens is:

1. the compiler first encounters res in main body;

2. it makes up an "implicit declaration" for res , based on what it can infer from the way res is called inside of main ; this implies an int return type, according to C conventions;

3. when the real res is found later on, a mismatch between the inferred signature (ie, return type) and the real one triggers the compilation error.

To fix it:

float res (float a, float b, float c);

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

    // 1st var
    NSLog(@"Hi, %f World!", res(1.0f, 2.0f, 3.0f));
  }
  return 0;
}

float res (float a, float b, float c)
{
  float res=a+b+c;
  return res;
}

Answer 2

You are just forgetting to declare function, just put

float res (float a, float b, float c);

before your int main

hope it helps you!

Answer 3

Try:

#import <Foundation/Foundation.h>

float res (float a, float b, float c)
{
    float res=a+b+c;
    return res;
}

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

    @autoreleasepool {


        // 1st var
        NSLog(@"Hi, %f World!", res(1.0f, 2.0f, 3.0f));

    }
    return 0;
}