warning: assignment makes pointer from integer without a cast error

Question

I was doing this exercise and I had to write a program that takes in a list of numbers and swaps pairs of numbers so they're in order:

void swapPairs(int* a[], int length)
{
   int i=0;
   int temp;
   while(i<(length-1))
   {
     if(a[i]>a[i+1])
     {
        temp=a[i];
        a[i]=a[i+1];
        a[i+1]=temp;
     }
     i++;
   }
}

int main()
{
  int array[]={2,1,3,1};
  swapPairs(array, 4);
  return 0;
}

I keep getting these errors:

In function ‘swapPairs’:
warning: assignment makes integer from pointer without a cast
     temp=a[i];
         ^

warning: assignment makes pointer from integer without a cast
     a[i+1]=temp;


In function ‘main’: warning: passing argument 1 of ‘swapPairs’ from incompatible pointer type
swapPairs(array, 4);
         ^

note: expected ‘int **’ but argument is of type ‘int *’
void swapPairs(int* a[], int length)
  ^

When I tried it with just an array instead of a pointer, it worked perfectly fine. Can someone please explain what is wrong with this and how to fix it?
Thanks in advance.

int* a[] change that to int a[]

KarimS
– KarimS

2015-05-10 21:51:10 +00:00
Commented May 10, 2015 at 21:51 — KarimS
– KarimS, Commented May 10, 2015 at 21:51

Mureinik · Accepted Answer · 2015-05-10 21:55:49Z

2

Your declaration of swapPairs is wrong - it shouldn't accept an array of int * (int pointers) - it should accept and an array of ints:

void swapPairs(int a[], int length)

answered May 10, 2015 at 21:55

Mureinik

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5 Comments

csbk Over a year ago

my question had two parts; first i had to write it with int a[] as the parameter and then say how i would change it if the parameter instead was int* a[]. thats the part i m stuck on

WhozCraig Over a year ago

@ajia that is also coincidentally the part you left out of your posted question. We're not mind-readers.

M.M Over a year ago

@ajia int *a[] is not "a list of numbers" as you said in your question. It would help if you showed the code which will call the version with int *a[]

csbk Over a year ago

I did. I have exactly the same code for both except the other one had just int a[] as a parameter instead.

csbk Over a year ago

nevermind. I think the question was wrong to begin with

Barry Gackle · Accepted Answer · 2015-05-10 23:25:52Z

1

The type of 'temp' is int. The type of 'a[i]' is *int (pointer to an int).

You are assigning the value of a pointer rather than the value of an integer because you are failing to dereference the pointer.

The while loop should read:

    while(i<(length-1))
    {
        if(*(a[i])>*(a[i+1]))
        {
             temp=*(a[i]);
             *(a[i])=*(a[i+1]);
             *(a[i+1])=temp;
        }
        i++;
    }

answered May 10, 2015 at 23:25

Barry Gackle

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