How to select multiple elements in an array with C?

Question

Is there a way to select multiple elements in array using one line of code in C? For instance, say I had the following code (assuming I already asked the user for twenty numbers, the first ten I asked to be positive and the last ten I asked to be negative):

if (myArray[0 through 9] > 0)
{
  printf("Thank you for providing positive numbers!");
}
else
{
  printf("Sorry, please try again!");
}

if (myArray[10 through 19] < 0)
{
  printf("Thank you for providing negative numbers!");
}
else
{
  printf("Sorry, please try again!");
}

What code could I substitute for "through"? I am fairly new to this language, and have never heard of a way of doing so. I know that with this particular code I could make two arrays, one for the positive numbers and one for the negative numbers, but I am curious to know for other programming projects.

Thank you for reading and answering!

There's no array slicing, you'd have to do it yourself, with a loop, most likely — Ben
– Ben, Commented Jul 17, 2014 at 14:49

Barmar · Accepted Answer · 2014-07-17 14:50:26Z

3

There's nothing built-in that does it, you need to write a loop. Don't forget that array indexes start at 0.

int all_positive = 1;
int i;
for (i = 0; i < 10; i++) {
    if (myArray[i] <= 0) {
        all_positive = 0;
        break;
    }
}
if (all_positive) {
    printf("Thank you for providing positive numbers!\n");
}

answered Jul 17, 2014 at 14:50

Barmar

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Terryn Over a year ago

Okay thank you I wasn't sure if there was or not, so I will use loops instead. And thank you for pointing out that I wrote one instead of zero! I will fix that.

Vlad from Moscow · Accepted Answer · 2014-07-17 15:07:11Z

0

int a[20];

// entering values for the array

_Bool first_positive = 1;

for ( size_t i = 0; i < 10 && first_positive; i++ )
{
   first_positive = 0 < a[i];
}

if ( first_positive ) puts( "Hura, first 10 elements are positive" );

_Bool last_negative = 1;

for ( size_t i = 10; i < 20 && last_negative; i++ )
{
   last_negative = a[i] < 0;
}

if ( last_negative ) puts( "Hura, last 10 elements are negative" );

Instead of type name _Bool you can use type int if your compiler does not support _Bool

edited Jul 17, 2014 at 15:07

answered Jul 17, 2014 at 14:56

Vlad from Moscow

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Comments

Radar Blue · Accepted Answer · 2016-08-28 18:09:25Z

0

The program requests number of rows (1D array). Then asks for 2 integers, whole numbers. Then asks user to select 2 rows. The sum of the 2 selected rows is then added.

   #include <stdio.h>
   int main ()
   //1D_Array. Load Element and Add Sumline .
   //KHO2016.no5. mingw (TDM-GCC-32) . c-ansi .
   {
   //declare
   int a,b,c,d,e,sum1=0;
   int array[50];
   int i,j,elm1,elm2;

   //valuate
   printf ("Plot a number of elements [1 - 20]: ");
   scanf ("%d",&a);
   printf ("Plot a value : ");
   scanf ("%d",&b);
   printf ("Plot an increment value : ");
   scanf ("%d",&c);

   //calculate
   {for (i<0;i<=a;i++)
   {array[i] =(b+(++c)); // set value for variable [i], inside the array subscript. the vairable [i] must have an INT, and an increment to function !
   sum1 = (sum1 + array[i]);
   printf ("Row [%.2d] : %.2d + %.2d = %d\n",i,b,c,array[i]);}
   printf ("\nSum total = %d\n",sum1);} 
   printf ("\nRow [%.2d] = %d\n",b,array[b]);
   printf ("Row [%.2d] = %d\n",a,array[a]);
   printf ("Select 2 Rows :\n");
   scanf ("%d%d",&elm1,&elm2);
   d=elm1;
   e=elm2;

   printf ("You selected Row [%.2d] = %d\n",d,array[d]);
   printf ("You selected Row [%.2d] = %d\n",e,array[e]);
   printf ("The sum of two selected Rows [%d]+[%d] : %d + %d = %d\n",d,e,array[d],array[e],array[d]+array[e]);
   //terminate
   return 0;
   }

edited Aug 28, 2016 at 18:09

answered Aug 27, 2016 at 17:36

Radar Blue

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David Ranieri Over a year ago

It seems that you are answering another question.

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