Thread: Returning an Array

  1. #1
    Registered User mmarab's Avatar
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    Question Returning an Array

    Hi i undestand that in C you can not return an array, but a pointer to an array. But i am having trouble doing this, this is what i have done do far:

    Code:
    char * numberCon()
    {
       char numbers[10]
        for()
       {
         //adds numbers into the array
       }
       
      return numbers;
    }
    
    int main()
    {
      char * pt = numberCon();
      int i =0;
     for(;i<10;i++)
     {
       printf("%d", &pt);
       pt++;
     }
    }
    doing this the compiler gives me the following warning: "Suspicious pointer conversion in function numberCon" and also the incorrect values are printed out.

    Any help would be great.

  2. #2
    erstwhile
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    Your numbers variable only has scope local to the numberCon function. When the function returns whatever 'pt' has a hold of will be garbage, hence the incorrect values.

    Either make numbers static or dynamically allocate memory and return a pointer to that, remembering to free it when done.
    CProgramming FAQ
    Caution: this person may be a carrier of the misinformation virus.

  3. #3
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    The problem of yours is simple. You just misunderstood the difference between and numbers[10] defined string and a char * defined string. s points and adress right. But you can not assign that to an empty string adress,coz numbers keeps an adress that points a 10 charactered string.So you should change you numbercon function like this:


    return &numbers[0];

  4. #4
    Woof, woof! zacs7's Avatar
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    Quote Originally Posted by ozumsafa View Post
    The problem of yours is simple. You just misunderstood the difference between and numbers[10] defined string and a char * defined string. s points and adress right. But you can not assign that to an empty string adress,coz numbers keeps an adress that points a 10 charactered string.So you should change you numbercon function like this:


    return &numbers[0];
    No you shouldn't, that won't make a difference. See Ken Fitlike's post.

  5. #5
    Chinese pâté foxman's Avatar
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    There's also the classic solution, that's it, passing "an array" to your numberCon fonction, which could looks like this

    Code:
    char *numberCon(char *array, int arraySize)
    {
    	int i;
    
    	for (i = 0; i < arraySize; i++)
    	{
    		//...
    	}
    
    	return array;
    }
    
    
    int main()
    {
    	char numbers[10];
    	char *pt;
    
    	pt = numberCon(numbers, 10);
    
    	//...
    
    	return 0;
    }
    Anyway.

  6. #6
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    He is right. Forget about my post. That was an uncareful one anyway. I do not have the time right now . But I had a look again , the structure is in pain. First of all you shouldnt set an algorithm like that. You have also some operator errors. Based on what I saw in limited time. I will try to write more later.

  7. #7
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    by operator I mean : &pt

  8. #8
    Registered User MacNilly's Avatar
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    Redundant

    Quote Originally Posted by foxman View Post
    There's also the classic solution, that's it, passing "an array" to your numberCon fonction, which could looks like this

    Code:
    char *numberCon(char *array, int arraySize)
    {
    	int i;
    
    	for (i = 0; i < arraySize; i++)
    	{
    		//...
    	}
    
    	return array;
    }
    
    
    int main()
    {
    	char numbers[10];
    	char *pt;
    
    	pt = numberCon(numbers, 10);
    
    	//...
    
    	return 0;
    }
    Anyway.
    Arrays are passed "by reference" by default in C. There is no reason why you need to be returning the array from that function (or any function in C for that matter). The contents will be modified in the caller.

  9. #9
    Hurry Slowly vart's Avatar
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    There is no reason why
    same reason as in strcpy... for the calling chain support for example
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    – David J. Wheeler

  10. #10
    Registered User MacNilly's Avatar
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    Quote Originally Posted by vart View Post
    same reason as in strcpy... for the calling chain support for example
    Indeed. I stand corrected.
    Last edited by MacNilly; 07-19-2007 at 05:42 AM.

  11. #11
    Chinese pâté foxman's Avatar
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    Arrays are passed "by reference" by default in C. There is no reason why you need to be returning the array from that function (or any function in C for that matter). The contents will be modified in the caller.
    I know that. I just wanted my function to return something, it's free for you to use or not use the return value.

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