Thread: merge arrays homework struggle

The good news is that I have the program working.

The problem is that I am getting a "assignment from incompatible pointer type" warning when I compile. For example, in line 26.

The pointers are declared as doubles, the arrays pointed to are doubles, the function prototypes are defined with double type arrays.

I'm sure it's something stupid that I just don't understand.

Code:

#include <stdio.h>
#include <stdlib.h>

int array_input ( double user[] );

void array_sort ( double user[], int limit );

int array_combined ( double A[], double B[], double C[], int a_loop, int b_loop );

int main()
{
    int limit = 1000;                               // limit of array size
    double A[limit], B[limit], C[ 2 * limit];       // 1,2, and 3 arrays
    int junk = 0, loop, a_loop, b_loop, c_loop;     // loop and array variables
    double *puser, *puser_B, *puser_C;              // pointer declaration
    char yes;                                       // user controlled loop

    // user controlled loop
    while (junk == 0 )
    {

    printf("Enter the numbers in the first array.\n");
    fflush(stdin);

// function call for user input of first array
    puser = &A;
    a_loop = array_input( puser );

    printf("Enter the numbers in the second array.\n");
    fflush(stdin);

// function call for user input of second array
    puser = &B;
    b_loop = array_input( puser );


    // function call to sort first array
    printf("\nThe first set of numbers sorted in descending order are:\n");
    puser = &A;
    array_sort( puser, a_loop );


// function call to sort second array
    printf("\nThe second set of numbers sorted in descending order are:\n");
    puser = &B;
    array_sort( puser, b_loop );


    // function call to combine arrays
    puser = &A;
    puser_B = &B;
    puser_C = &C;
    c_loop = array_combined ( puser, puser_B, puser_C, a_loop, b_loop );


    // function call to sort combined array
    array_sort( puser_C, c_loop );

    printf("\n");


     printf("\nThe combined loop is:\n");
     for ( loop=0; loop < c_loop; loop++)
        printf("%.1f\n",C[loop]);


    printf("Would you like to run the program again? y for yes\n");
    fflush(stdin);
    scanf("%c", &yes);

    if (yes != 'y')
    exit(0);
    }
    return 0;
}


// input array
int array_input ( double user[] )
{
    int loop = 0, x, finished;       // looping variable
    char yes;                        // user controlled variable

while ( finished == 0) {

    while (scanf("%lf",&user[loop]))
    {
        loop++;
    }

    printf("Do you want to stop entering numbers? y for yes.\n");
    fflush(stdin);
    scanf("%c", &yes);

    if ( yes == 'y' ) {
        finished = 1;
    }

    if ( yes != 'y')
        printf("Enter the next number >");
}

    printf("The numbers you entered were:\n");
    for ( x=0; x < loop; x++)
        printf("%.1f\n",user[x]);


    return (loop);
}


void array_sort ( double user[], int limit )
{
    int loop,x;             // loop variables
    double temp;            // temp variable

    // set limit of array size
        loop = limit;
    // shorten array after largest moved to end
      for ( x = 1 ; x < loop  ; x++ )
        {
        // loop to move highest number to end of array
        for (limit = 0; limit < loop - x ; limit++)
            {
               if ( user[limit] < user[limit+1] )
               {
                   temp = user[limit+1];
                   user[limit+1] = user[limit];
                   user[limit] = temp;
               }
            }
        }

    // print sorted array
    for ( x=0; x < loop; x++)
        printf("%.1f\n",user[x]);

}

// function to combine arrays
int array_combined ( double A[], double B[], double C[], int a_loop, int b_loop )
{
   int x=0, y=0, z=0,w;   // loop variables

// combine arrays to point where size of arrays are equal
 while(x < a_loop && y < b_loop )
 {
  if(A[x] <= B[y])
   {
   C[z]=A[x];
   x++;
   z++;
   }
  else
   {
   C[z]=B[y];
   z++;
   y++;
   }
 }

// if A is larger, add in remaining elements of A

 while( x < a_loop )
  {
  C[z]=A[x];
  x++;
  z++;
  }

// if B is larger, add in remaining elements of B

 while( y < b_loop )
  {
  C[z]=B[y];
  z++;
  y++;
  }

  // eliminate duplicates
  for( x = 0; x < z; x++ )
{
   for( y = x + 1; y < z; )
   {
      if( C[y] == C[x])
      {
         for( w = y; w < z ; w++ )
             C[w] = C[w+1];
          z--;
      }
      else
         y++;
   }
}

  return(z);
}

The good news is that I have the program working.

The problem is that I am getting a "assignment from incompatible pointer type" warning when I compile. For example, in line 26.

First if that second line is true then the first line is necessarily false.

There are several problems with your code:

First do you realize that you are trying to use VLA (Variable Length Arrays)? This feature is only guaranteed to be available when compiling with a C99 compatible compiler. Since you seem to be using the Microsoft compiler I recommend you stop using this feature, since this compiler is not C99 compliant. I'd recommend you #define the constant outside of main() to avoid this issue.

Second fflush() is only defined in the standard to work with output streams, using it on input streams is undefined. You can eliminate the need for most of your fflush() calls by changing your scanf() calls to fix the problem. Put a space before the percent symbol to skip leading whitespace.

Code:

scanf(" %c", &someCharacterVariable);

Third since A[] is an array the name of the array without any brackets (A) is a pointer to the first element, so no need for the ampersand.

Jim

Originally Posted by jimblumberg

Third since A[] is an array the name of the array without any brackets (A) is a pointer to the first element, so no need for the ampersand.

or you could use &A[0].