How can i return a char with array in function to main?

[anyone94]

char* category (int aqi)
{
char *p;
if(aqi>=0 && aqi<=50)
p="Good";
else if(aqi>=51 && aqi<=100)
p="Moderate";
else if(aqi>=101 && aqi<=200)
p="Unhealthy";
else if(aqi>=201)
p="Hazarhous;
else
p="Nothing";
return p;
}

[anyone94]

the output didnt show any character,how to solve it?

[cire]

There is no output, because nothing is output. Showing actual code that you know compiles and reproduces the problem you're experiencing is advised -- this won't compile.

[anyone94]

#include<stdio.h>
char category(int aqi);
int main()
{
char aqr[20];
//enter aqr
aqr[20] = category(aqi);
return 0;
}
char category(int aqi)
{
char x[20];
if(aqi>300 && aqi<401)
x[20]= 'Good';
else if(aqi>401)
x[20]='Unhealthy';
else
x[20]='Nothing';
return x;
}



base on the code on above,is it right to return a char with array to main or how to using strcpy to do it?or how to slove it?i nid to return the status to main

[jlb]

base on the code on above,is it right to return a char with array to main

As shown above, no it is not correct. First you declared your function to return a single character, not an array. Second even if you did declare your function to return a char* you can't return an array that is local to your function. Third you really should study up on Arrays and Character Sequences. Start with these two links: http://www.cplusplus.com/doc/tutorial/arrays/ and http://www.cplusplus.com/doc/tutorial/arrays/ and I also suggest you study up a little on Pointers: http://www.cplusplus.com/doc/tutorial/pointers/


But you really should learn to use the std::string class instead of the C-strings, it will make your life much easier.

Something like the following may work.

#include <iostream>

using namespace std;

const char* category (int aqi);

int main()
{
   const char* test;
   test = category(60) ;
   std::cout << test << std::endl;

}
const char* category (int aqi)
{
   const char *p;
   if(aqi>=0 && aqi<=50)
      p="Good";
   else if(aqi>=51 && aqi<=100)
      p="Moderate";
   else if(aqi>=101 && aqi<=200)
      p="Unhealthy";
   else if(aqi>=201)
      p="Hazarhous";
   else
      p="Nothing";
   return p;
}

[anyone94]

can u show me how to return an array from a function to main,i m a student now,only start to learn c++.

[anyone94]

but now i hvt learn about std::string,my school only teach the basic one.can u show me a basic code that can return a char with an array?

[jlb]

The best way to "return" and array from a function would be to pass that array to your your function as a parameter. Or even better yet use the standard string class.

void category (char *test, int aqi);
string category(int aqi);

int main()
{
   char test[100];
   category(test, 60);
   cout << test << endl;

   string mstring = category(60);
   cout << mstring << endl;
   return(0);
}

void category (char *test, int aqi)
{
   strcpy(test,"Moderate");
}

string category(int aqi)
{
   string retVal = "Moderate";

   return retVal;
}

[anyone94]

Because this is my assignment,so the question mention that must follow:
o Parameter : int aqi
o Return type : string
o Determine air quality result based on the following table:

If that, i can use the code like your reply on above?

[jlb]

If that, i can use the code like your reply on above?

I would say yes, if your definition of string is to use std::string, the following returns a string from the function.

string category(int aqi)
{
   string retVal = "Moderate";

   return retVal;
}

You may want to read up on the string class. http://www.cplusplus.com/reference/string/string/string/

[anyone94]

Are your string refer to any means or variables ?Because if i follow your code on above,i get syntax error there.

[jlb]

Your question doesn't really make sense. A "string" is a standard C++ class. Please study the link I provided above.

[anyone94]

Ok, thx ya!